"Stormin Mormon" wrote:

Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.


In the winter I have to run the furnace or it gets cold. That means heat leaks out.

If it is leaking out, don't put as much in to leak out while you are gone.

Simple

Wes

"jeff_wisnia" wrote in message
eonecommunications...
Ed Huntress wrote:

"Ignoramus10802" wrote in message
...

On 2009-10-29, ATP* wrote:

True. Yet I still hear this type of "reasoning" all the time. Should be
a
simple concept even for the technically challenged, for example, people
who
argued here that you can compress air and allow it to expand (while
doing no
useful work) with no loss of energy.

That would be almost possible if compressing and expanding was done
very quickly, before compressed air cools.

i


But it has to be done *awfully* quickly. That's why there's a minimum
cylinder size for diesel engines -- something like 300 cc. Below 3,000
rpm or so, the compressed air cools too quickly to ignite the fuel. And
heat transfer gets worse as compression goes up.


That statement may not be entirely correct, Ed.

Remembering waaaay back to my childhood playing around with control line
model aircraft. before the glow plug engine was developed we had but two
choices, conventional spark plug engines and diesel engines.

g I had one of those. They weren't really diesels (technically, they're
"homogeneous charge, compression-ignition engines), but that isn't the
issue, because they ignite from compression, the same as a true diesel. The
issue is that they use ether for fuel, or an ether-diesel mix in the larger
ones, and ether has a cetane rating of 86. Diesel fuel runs around 40 - 45
cetane. Those little engines can't produce enough heat from compression to
ignite diesel fuel.


The diesels were never very popular, but they are still being made for
thos who want to add a bit of "authenticity" to replicas of vintage model
aircraft. Those are surely far below 300 cc, but the fuel they burn may
not be quite the same as what cars and trucks use. G

http://www.eifflaender.com/enginepics.htm

I also remember my not terribly successful efforts at flying RC models
back then. My ham ticket let me do that legally on 28 Mhz (the 10 meter
ham band) using a one tube receiver in the plane which triggered a rubber
band energized "escapement" that moved a combination rudder-stabilizer at
the rear of the plane.

A tail-wagger. I built one of those, a Cessna Birddog from a kit, with an
..049 Babe Bee engine. I used a salvaged CB walkie-talkie for a transmitter
and a homebrew superregen receiver. The signal was CW. I made the escapement
from a tin can, with bits of HSS hacksaw blade soldered onto the tips of the
arms. It flew pretty well, but I was not much of a pilot. Fortunately, if
you just tossed the transmitter aside, it would land by itself.


How the heck I just remembered that the tube used in those receivers was
an RK61, a gas filled triode, I'll never understand.

For the same reason that I remember that my first homebrew regen receiver, a
battery-powered rig that I built in 1957, used a 1T4. Our memories of old
stuff tend to hang in there while we forget what we had for breakfast. d8-)


http://tubedata.milbert.com/sheets/138/r/RK61.pdf

Thaks for the mammaries though.

Jeff

sigh That's most of what I'm good for these days. Sometimes I feel like an
antique. d8-(

--
Ed Huntress

"Ignoramus10802" wrote in message
...
On 2009-10-29, Ed Huntress wrote:

"Ignoramus10802" wrote in message
...
On 2009-10-29, Don Foreman wrote:
Savings begins the instant inside temperature is reduced, whether or
not it is stable at a lower setpoint. This is true regardless of how
well the house is insulated, what the thermal mass might be, who the
president is, which party controls congress or whether DOE likes it or
not. Rate of heat loss at any (and every) instant depends upon
temperature gradient from inside to outside.

Very well put.

But it has little to do with the question of whether you get any
significant
energy savings from turning down the thermostat for relatively short
periods
of time.

Again, if you shut it down for eight hours and the temperature drops,
say,
12 - 15 degrees F (typical for my house), you will spend hours waiting
for
the temperature to climb back up -- and (you do the calculus, not me g)
the benefit you get from it is LESS than the theoretical savings you
would
have if you lived in a vacuum bottle and the temperature had dropped only
6
or 7 degrees for all of that time. Meanwhile, you're freezing your butt
off,
part of the time at close to 12 degrees lower than your regular setting.

Are we together on this, Dr. Algebra?

Sure. Savings would be there, t possibly too small to overcome
inconvenience. The solution to this has been well known and it is
thermostats with a time schedule function.


Whether or not the savings on the energy bill is noticable is another
question depending on how much the setback was for how long.

I wonder how much the DOE spent on a study to address what would be an
easy test question in thermodynamics 101.

That study might have been a part of economic stimulus.

You guys had better figure in thermal mass and look up some values for
thermal mass versus R-values in a typical house. The calculation is not
as
simple as you make it out to be. For a short time, as DOE says, the
saving
is trivial.


Yes, but it is still there, which is the point.

i

So is my hair, more or less, but I wouldn't make a big deal about it. d8-)

--
Ed Huntress

In article ,
Jon Elson wrote:
:Pete C. wrote:
:
: No, it isn't. It was documented on a well monitored high efficiency
: model home where the backup heat strips on the high efficiency heat pump
: were kicking in in order to provide a reasonable temp recovery time
: since the heat pump itself did not have the capacity. The electricity
: used during the temp recovery was more than would have been used on temp
: maintenance due to the switch to lower efficiency backup (100% vs.
: 300%+).
:
:OK, this is a killer example, where the furnace efficiency goes down the
:tubes when it needs to raise the temp suddenly. It might be possible to
:stage the temp rise to avoid that with a suitable thermostat.
:
:But, many other heating systems have no such penalty for a rise in temp
:setting, such as a traditional gas forced-air furnace.

My gas furnace is 2-stage, and not particularly exotic (a common Trane
model, 80,000 BTU). Presumably it's more efficient when operating on
low-heat, as otherwise there's little point in the added complexity of a
2-stage burner and control. Except in really extreme weather, the only
time it runs on high-heat is during recovery from night time setback.

--
Bob Nichols AT comcast.net I am "RNichols42"

Ed Huntress wrote:
"jeff_wisnia" wrote in message
eonecommunications...

Ed Huntress wrote:


"Ignoramus10802" wrote in message
...


On 2009-10-29, ATP* wrote:


True. Yet I still hear this type of "reasoning" all the time. Should be
a
simple concept even for the technically challenged, for example, people
who
argued here that you can compress air and allow it to expand (while
doing no
useful work) with no loss of energy.

That would be almost possible if compressing and expanding was done
very quickly, before compressed air cools.

i

But it has to be done *awfully* quickly. That's why there's a minimum
cylinder size for diesel engines -- something like 300 cc. Below 3,000
rpm or so, the compressed air cools too quickly to ignite the fuel. And
heat transfer gets worse as compression goes up.


That statement may not be entirely correct, Ed.

Remembering waaaay back to my childhood playing around with control line
model aircraft. before the glow plug engine was developed we had but two
choices, conventional spark plug engines and diesel engines.


g I had one of those. They weren't really diesels (technically, they're
"homogeneous charge, compression-ignition engines), but that isn't the
issue, because they ignite from compression, the same as a true diesel. The
issue is that they use ether for fuel, or an ether-diesel mix in the larger
ones, and ether has a cetane rating of 86. Diesel fuel runs around 40 - 45
cetane. Those little engines can't produce enough heat from compression to
ignite diesel fuel.


The diesels were never very popular, but they are still being made for
thos who want to add a bit of "authenticity" to replicas of vintage model
aircraft. Those are surely far below 300 cc, but the fuel they burn may
not be quite the same as what cars and trucks use. G

http://www.eifflaender.com/enginepics.htm

I also remember my not terribly successful efforts at flying RC models
back then. My ham ticket let me do that legally on 28 Mhz (the 10 meter
ham band) using a one tube receiver in the plane which triggered a rubber
band energized "escapement" that moved a combination rudder-stabilizer at
the rear of the plane.


A tail-wagger. I built one of those, a Cessna Birddog from a kit, with an
.049 Babe Bee engine. I used a salvaged CB walkie-talkie for a transmitter
and a homebrew superregen receiver. The signal was CW. I made the escapement
from a tin can, with bits of HSS hacksaw blade soldered onto the tips of the
arms. It flew pretty well, but I was not much of a pilot. Fortunately, if
you just tossed the transmitter aside, it would land by itself.


How the heck I just remembered that the tube used in those receivers was
an RK61, a gas filled triode, I'll never understand.


For the same reason that I remember that my first homebrew regen receiver, a
battery-powered rig that I built in 1957, used a 1T4. Our memories of old
stuff tend to hang in there while we forget what we had for breakfast. d8-)


http://tubedata.milbert.com/sheets/138/r/RK61.pdf

Thaks for the mammaries though.

Jeff


sigh That's most of what I'm good for these days. Sometimes I feel like an
antique. d8-(


A small diesel here
http://www.model-engineer.co.uk/albu...=6778&p=123122
, about 28cc, not sure about the relation of lamp oil to pump diesel but
it sounds less volatile than the small "diesel" aircraft engines I used
on occasions which were a blend of ether, caster oil and amyl nitrate.
Last time I used one was about 1981 and on returning to the US from the
UK I asked my chemistry teacher about getting some ether to blend my
own and she almost had a fit, then gave me a lecture about the dangerous
nature of ether. Didn't know then that engine start spray is mostly
ether and have seen a thread elsewhere where a chap detailed using it to
refill a capillary temperature gauge, Lucas IIRC.

David Billington wrote:

Ed Huntress wrote:
"jeff_wisnia" wrote in message
eonecommunications...

Ed Huntress wrote:


"Ignoramus10802" wrote in message
...


On 2009-10-29, ATP* wrote:


True. Yet I still hear this type of "reasoning" all the time. Should be
a
simple concept even for the technically challenged, for example, people
who
argued here that you can compress air and allow it to expand (while
doing no
useful work) with no loss of energy.

That would be almost possible if compressing and expanding was done
very quickly, before compressed air cools.

i

But it has to be done *awfully* quickly. That's why there's a minimum
cylinder size for diesel engines -- something like 300 cc. Below 3,000
rpm or so, the compressed air cools too quickly to ignite the fuel. And
heat transfer gets worse as compression goes up.


That statement may not be entirely correct, Ed.

Remembering waaaay back to my childhood playing around with control line
model aircraft. before the glow plug engine was developed we had but two
choices, conventional spark plug engines and diesel engines.


g I had one of those. They weren't really diesels (technically, they're
"homogeneous charge, compression-ignition engines), but that isn't the
issue, because they ignite from compression, the same as a true diesel. The
issue is that they use ether for fuel, or an ether-diesel mix in the larger
ones, and ether has a cetane rating of 86. Diesel fuel runs around 40 - 45
cetane. Those little engines can't produce enough heat from compression to
ignite diesel fuel.


The diesels were never very popular, but they are still being made for
thos who want to add a bit of "authenticity" to replicas of vintage model
aircraft. Those are surely far below 300 cc, but the fuel they burn may
not be quite the same as what cars and trucks use. G

http://www.eifflaender.com/enginepics.htm

I also remember my not terribly successful efforts at flying RC models
back then. My ham ticket let me do that legally on 28 Mhz (the 10 meter
ham band) using a one tube receiver in the plane which triggered a rubber
band energized "escapement" that moved a combination rudder-stabilizer at
the rear of the plane.


A tail-wagger. I built one of those, a Cessna Birddog from a kit, with an
.049 Babe Bee engine. I used a salvaged CB walkie-talkie for a transmitter
and a homebrew superregen receiver. The signal was CW. I made the escapement
from a tin can, with bits of HSS hacksaw blade soldered onto the tips of the
arms. It flew pretty well, but I was not much of a pilot. Fortunately, if
you just tossed the transmitter aside, it would land by itself.


How the heck I just remembered that the tube used in those receivers was
an RK61, a gas filled triode, I'll never understand.


For the same reason that I remember that my first homebrew regen receiver, a
battery-powered rig that I built in 1957, used a 1T4. Our memories of old
stuff tend to hang in there while we forget what we had for breakfast. d8-)


http://tubedata.milbert.com/sheets/138/r/RK61.pdf

Thaks for the mammaries though.

Jeff


sigh That's most of what I'm good for these days. Sometimes I feel like an
antique. d8-(


A small diesel here
http://www.model-engineer.co.uk/albu...=6778&p=123122
, about 28cc, not sure about the relation of lamp oil to pump diesel but
it sounds less volatile than the small "diesel" aircraft engines I used
on occasions which were a blend of ether, caster oil and amyl nitrate.
Last time I used one was about 1981 and on returning to the US from the
UK I asked my chemistry teacher about getting some ether to blend my
own and she almost had a fit, then gave me a lecture about the dangerous
nature of ether. Didn't know then that engine start spray is mostly
ether and have seen a thread elsewhere where a chap detailed using it to
refill a capillary temperature gauge, Lucas IIRC.

I believe "lamp oil" is deodorized kerosene K1, pretty much like
"winter" diesel D1.

Echoing what Robert Nichols said:

I'm in the midst of optimizing a brand new, Bryant 80% forced air, 2
stage, 110k Btu furnace. It sucks every BTU out of things when running
in the low fire mode. On high fire it is just trying to get you
comfortable enough to let it get back to the economy mode. I doubt that
the difference is more than a few percent but I suspect it is
measurable. If nothing else, the high fire mode requires the high speed
fan and attendant increase in electrical use.

Jon Elson wrote:
Pete C. wrote:

No, it isn't. It was documented on a well monitored high efficiency
model home where the backup heat strips on the high efficiency heat pump
were kicking in in order to provide a reasonable temp recovery time
since the heat pump itself did not have the capacity. The electricity
used during the temp recovery was more than would have been used on temp
maintenance due to the switch to lower efficiency backup (100% vs.
300%+).

OK, this is a killer example, where the furnace efficiency goes down the
tubes when it needs to raise the temp suddenly. It might be possible to
stage the temp rise to avoid that with a suitable thermostat.

But, many other heating systems have no such penalty for a rise in temp
setting, such as a traditional gas forced-air furnace.

Jon

On Thu, 29 Oct 2009 10:54:59 -0500, the infamous Ignoramus10802
scrawled the following:

On 2009-10-29, Pete C. wrote:

Ignoramus10802 wrote:

On 2009-10-29, Stormin Mormon wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.


Imagine for a minute that you have to leave house for a month.

Would it be energy efficient to turn thermostat down? Of course, as
less heat will be produced for a whole month, with only a few minutes
to catch up.

The same applies to only one day.

i

It's far more complicated than that. Factors such as insulation / heat
loss, type of heating, multi-stage heating, electric backup heat on heat
pumps, etc. all come into play in determining the away duration and temp
reduction where savings begin, and in some cases (typically high
efficiency homes) it can require a multi day absence to see any savings.

This is patently untrue.

Think about what you just said, Ig. The better insulated homes can go
days without an injection of heat or cooling. Poorly insulated homes
can't go an hour without in exteme climes. Using a setback thermostat
in a well insulated home has much less impact (if any for a day) than
it does in a leaky old shack. Your comment was the untruth.

I've used setback thermometers since 1975, when I got my first home.
(It was a leaky old shack, but that wasn't too bad in temperate LoCal)

--
"Giving every man a vote has no more made men wise and free
than Christianity has made them good." --H. L. Mencken
---

Stormin Mormon wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.

I have a programmable thermostat that go goes from 68F to 60F shortly
after I leave for work till just before I arrive home, then again
about 11PM till 5AM when I get up. Hard to say if it's made a
significant difference, but I installed the thermostat when I had to
replace my furnace in 2001 and I haven't really tracked the gas use.
My house was built in 1894 and has little insulation, temperature in
the winter can vary 8-10 degrees from near the heat register to the
farthest corner of the living room.

David

Let the Record show that "Pete C." on or about
Thu, 29 Oct 2009 13:30:44 -0500 did write/type or cause to appear in
rec.crafts.metalworking the following:

That isn't a "pair of heating systems", nearly all heat pumps include
backup heat strips for times when the heat pump is not able to produce
enough heat such as very cold weather / high demand.


In the case you've described, you aren't dealing just with the
thermodynamics of the situation. You're also adding the complexity of
multiple heat sources that operate under different circumstances.

That complexity exists everywhere and that was my point - you have to do
the actual analysis of the home in question to get the correct answer -
you can't rely on blanket statements / myths.

An additional complication is occupancy, since for folks who are retired
or work from home, or a stay at home spouse, you loose half or more of
your theoretical savings period with the occupants not being away during
the day.

OTOH., we can turn the heat down in the rest of the house, warm
just the office, and double up the blankets at night. Just don't let
the pipes freeze. B-) (that means no coffee.)


pyotr
-
pyotr filipivich
We will drink no whiskey before its nine.
It's eight fifty eight. Close enough!

Let the Record show that Lewis Hartswick on
or about Thu, 29 Oct 2009 06:53:05 -0600 did write/type or cause to
appear in rec.crafts.metalworking the following:
Stormin Mormon wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.

That is another one of those, " It Depends".
In this case on how long you will be gone.

Bingo. How long will you be gone, how low you set it, and how
fast does it take for the inside to cool down, and warm back up. If I
live where it is below freezing all the time, and the house is drafty
- I may shut the heat down more when I go out, because I can't afford
to heat all of Kansas! (OTOH, I might want to stand downwind of the
house and enjoy the heat I am paying for.)
If I have a snug warm house, that doesn't cool rapidly (lots of
thermal mass) then it doesn't matter _as much_.

When you come back, what are you going to do? Cooking dinner in
the oven is a good for reheating a house - or at least the kitchen.
B-)

And so it goes.
-
pyotr filipivich
We will drink no whiskey before its nine.
It's eight fifty eight. Close enough!

Let the Record show that jeff_wisnia
on or about Thu, 29 Oct 2009 15:59:36 -0400 did write/type or cause to
appear in rec.crafts.metalworking the following:

Poll question:

How many guys here have wives who mistakenly think that when warming up
a cooled down house the rate of temperature change produced by a typical
home heating system will be faster if they shove the thermostat setting
all the way up to 90F than if they just move it to the appropriate setpoint.

Then of course, they forget to reset it when the place reaches a
comfortable temperature which some time later causes the man of the
house to snarl, "Why the hell is it so damn hot in here?"

Ah, but there is a difference here. As I heard it, God created
Adam, and he said "Yoicks its hot! I can't wait to invent air
conditioning." Shortly afterwards, God takes advantage of Adam
knocking himself out trying, and creates Eve. Her first words are
"Good God, it's cold in here, why not create some warm clothes and
central heat!"
And it has been a problem ever since.
-
pyotr filipivich
We will drink no whiskey before its nine.
It's eight fifty eight. Close enough!

pyotr filipivich wrote:

Let the Record show that "Pete C." on or about
Thu, 29 Oct 2009 13:30:44 -0500 did write/type or cause to appear in
rec.crafts.metalworking the following:

That isn't a "pair of heating systems", nearly all heat pumps include
backup heat strips for times when the heat pump is not able to produce
enough heat such as very cold weather / high demand.


In the case you've described, you aren't dealing just with the
thermodynamics of the situation. You're also adding the complexity of
multiple heat sources that operate under different circumstances.

That complexity exists everywhere and that was my point - you have to do
the actual analysis of the home in question to get the correct answer -
you can't rely on blanket statements / myths.

An additional complication is occupancy, since for folks who are retired
or work from home, or a stay at home spouse, you loose half or more of
your theoretical savings period with the occupants not being away during
the day.

OTOH., we can turn the heat down in the rest of the house, warm
just the office, and double up the blankets at night. Just don't let
the pipes freeze. B-) (that means no coffee.)

Well, ideally you should be zoning and not heating long unoccupied rooms
beyond maintenance level anyway. Certainly I have the dampers mostly
closed on my spare bedroom and dining room pretty much all the time,
only opening them on the rare occasion those rooms will be occupied.

On Thu, 29 Oct 2009 12:46:13 -0400, "Ed Huntress"
wrote:


"Bill Noble" wrote in message
...


"Ignoramus10802" wrote in message
...
On 2009-10-29, Pete C. wrote:

Ignoramus10802 wrote:

On 2009-10-29, Stormin Mormon
wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.


Imagine for a minute that you have to leave house for a month.

Would it be energy efficient to turn thermostat down? Of course, as
less heat will be produced for a whole month, with only a few minutes
to catch up.

The same applies to only one day.

i

It's far more complicated than that. Factors such as insulation / heat
loss, type of heating, multi-stage heating, electric backup heat on heat
pumps, etc. all come into play in determining the away duration and temp
reduction where savings begin, and in some cases (typically high
efficiency homes) it can require a multi day absence to see any savings.

This is patently untrue.

I

Correct - whatever the net effect of insulation is, there is a net
negative heat flux from the house to the outside. The flux is
proportional to the temperature difference (the exact equation will depend
on the radiation, convection and conduction components - radiation alone
is governed by the Stephan-Boltzman equation). The larger the difference
the greater the flux. Averaged over any period of time, any time spent
with the thermostat set lower will yeild a lower internal temperature,
hence less heat flux. Whether that is enough to show up in your bill is
another question, but from a energy savings point of view, it is
incontestible.

The confounding issue, though, is the thermal mass of the house. That's why
the DOE explanation says that the savings occur when the temperature inside
the house has stabilized at the lower temperature.

When you shut off the furnace, the thermal mass of the inside of the house
is what's giving up heat to the outside. That's stored energy that came from
the furnace heat. When you raise the temperature, you have to restore that
heat to the thermal mass. So with the furnace off and the temperature inside
of the house dropping, you're losing stored heat. When you turn the
thermostat back on, you have to restore that lost heat, which will also heat
up the atmosphere inside of the house (which is a very small portion of the
total inside thermal mass).

Imagine a bucket with a pinhole leak near the bottom. Let's consider
the level of the water in the bucket as analogous to temperature in an
insulated enclosure. The diameter of the bucket determines the mass of
water needed to reach a given level. It's a valid analogy because
temperature is a measure of thermal potential, water height determines
pressure pushing water out the pinhole leak. Water leak rate is qty
of water per unit time, heat leak rate is qty of heat energy (Joules,
BTU, etc) per unit time.

Let's rig a little toilet-valve arrangement to maintain the level
except that it will have hysteresis: it will click on when water is
below a certain level and refil the bucket until the water rises some
incremental amount whereupon it will click off. Refill will stop and
the level will gradually go down because of the pinhole leak. How
long it takes to go down depends on the size of the leak (insulation)
and the diameter of the bucket (thermal mass).

I hope it's apparent that if the leakrate is 1 gallon per minute then
the average replenishment rate must also be 1 gallon per minute. If
it's less, the level will recede, if it's more the level will rise.

If we now lower the height of the toilet valve, there will be no
influx until the bucket leaks down to that level. If we then raise
the valve, the valve will stay open until the water has risen to that
level. But the average long-term water consumption will still be the
leakrate.

Note that this is true regardless of the diameter of the bucket.

It is true that both leak rates depend on potential (depth or
temperature difference) so differential equations are required to
express them correctly. This does not change the fact that what goes
in must equal what goes out long term if the long-term average
temperature is constant over several cycles of moving the setpoint up
and down.










That's what I read from their description, anyway, and it comports with
things I've read about it from other sources. There is no (theoretical) net
gain or loss when the thermal mass is put through the cycle of cooling down
and heating up. The savings occur when the temperature is reduced and
stabilized.

This all assumes that a house is decently insulated and that the thermal
mass of the house is substantial. Of course, the thermal differential
between the inside and outside temperatures are always at work, suggesting
that there is less heat loss with each degree of reduction of inside
temperature, as you say. But the DOE's reference to actual testing agrees
with the fact that, as soon as you turn the thermostat down, you begin
losing *stored* heat, and when you turn it back up, 100% of that lost heat
must be restored, regardless of actual thermal losses through the walls and
ceiling.

Let the Record show that "Pete C." on or about
Thu, 29 Oct 2009 23:04:40 -0500 did write/type or cause to appear in
rec.crafts.metalworking the following:

pyotr filipivich wrote:

Let the Record show that "Pete C." on or about
Thu, 29 Oct 2009 13:30:44 -0500 did write/type or cause to appear in
rec.crafts.metalworking the following:

That isn't a "pair of heating systems", nearly all heat pumps include
backup heat strips for times when the heat pump is not able to produce
enough heat such as very cold weather / high demand.


In the case you've described, you aren't dealing just with the
thermodynamics of the situation. You're also adding the complexity of
multiple heat sources that operate under different circumstances.

That complexity exists everywhere and that was my point - you have to do
the actual analysis of the home in question to get the correct answer -
you can't rely on blanket statements / myths.

An additional complication is occupancy, since for folks who are retired
or work from home, or a stay at home spouse, you loose half or more of
your theoretical savings period with the occupants not being away during
the day.

OTOH., we can turn the heat down in the rest of the house, warm
just the office, and double up the blankets at night. Just don't let
the pipes freeze. B-) (that means no coffee.)

Well, ideally you should be zoning and not heating long unoccupied rooms
beyond maintenance level anyway. Certainly I have the dampers mostly
closed on my spare bedroom and dining room pretty much all the time,
only opening them on the rare occasion those rooms will be occupied.

My problem is that the 'office' is the one room with the worst
heat. So I just turn the thermostat down for the house, and use a
space heater in the office, and in the bathroom. And dress warm.
-
pyotr filipivich
We will drink no whiskey before its nine.
It's eight fifty eight. Close enough!

Let the Record show that Gunner Asch on
or about Thu, 29 Oct 2009 21:52:22 -0700 did write/type or cause to
appear in rec.crafts.metalworking the following:
On Thu, 29 Oct 2009 20:39:27 -0700, pyotr filipivich
wrote:

Let the Record show that Lewis Hartswick on
or about Thu, 29 Oct 2009 06:53:05 -0600 did write/type or cause to
appear in rec.crafts.metalworking the following:
Stormin Mormon wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.

That is another one of those, " It Depends".
In this case on how long you will be gone.

Bingo. How long will you be gone, how low you set it, and how
fast does it take for the inside to cool down, and warm back up. If I
live where it is below freezing all the time, and the house is drafty
- I may shut the heat down more when I go out, because I can't afford
to heat all of Kansas! (OTOH, I might want to stand downwind of the
house and enjoy the heat I am paying for.)
If I have a snug warm house, that doesn't cool rapidly (lots of
thermal mass) then it doesn't matter _as much_.

When you come back, what are you going to do? Cooking dinner in
the oven is a good for reheating a house - or at least the kitchen.
B-)

And so it goes.
-

You in Kansas? My sister is single..and working for a Sherriffs
department in Kansas.....

Ooh, sounds interesting.

Alas, I have not lived in Kansas ... ack. Since before she was
born. There were only 48 states! No wait, that was after the start
of Camelot ... never mind. There were fifty. It just seems like it
was shortly after the glaciers receded, when the central sea dried
up...

Interested? Rather a hotty too as it happens.....

Not really my sister..but has been my "sister" for humm...20 yrs now. I
think she is 40..41ish.

If so..Ill turn you on to her face book page..and give you a strong
recommendation......

Alas, that is too far, or not far enough. I'm considering looking
into following the Boeing move.
-
pyotr filipivich
We will drink no whiskey before its nine.
It's eight fifty eight. Close enough!

On Thu, 29 Oct 2009 20:39:27 -0700, pyotr filipivich
wrote:

Let the Record show that jeff_wisnia
on or about Thu, 29 Oct 2009 15:59:36 -0400 did write/type or cause to
appear in rec.crafts.metalworking the following:

Poll question:

How many guys here have wives who mistakenly think that when warming up
a cooled down house the rate of temperature change produced by a typical
home heating system will be faster if they shove the thermostat setting
all the way up to 90F than if they just move it to the appropriate setpoint.

Then of course, they forget to reset it when the place reaches a
comfortable temperature which some time later causes the man of the
house to snarl, "Why the hell is it so damn hot in here?"

Ah, but there is a difference here. As I heard it, God created
Adam, and he said "Yoicks its hot! I can't wait to invent air
conditioning." Shortly afterwards, God takes advantage of Adam
knocking himself out trying, and creates Eve. Her first words are
"Good God, it's cold in here, why not create some warm clothes and
central heat!"
And it has been a problem ever since.
-

The Garden of Eden was obviously not in Minnesota. Minnesota Mary
thinks 40's is wet sheet weather while Bubba Don about can't sleep
unless he's sweating a little.

I can relate to Sam McGee, oh yeah! Don't bury me in cold Fort
Snelling, please, take me to a roaring furnace!

On Fri, 30 Oct 2009 02:02:27 -0500, Don Foreman
wrote:

On Thu, 29 Oct 2009 20:39:27 -0700, pyotr filipivich
wrote:

Let the Record show that jeff_wisnia
on or about Thu, 29 Oct 2009 15:59:36 -0400 did write/type or cause to
appear in rec.crafts.metalworking the following:

Poll question:

How many guys here have wives who mistakenly think that when warming up
a cooled down house the rate of temperature change produced by a typical
home heating system will be faster if they shove the thermostat setting
all the way up to 90F than if they just move it to the appropriate setpoint.

Then of course, they forget to reset it when the place reaches a
comfortable temperature which some time later causes the man of the
house to snarl, "Why the hell is it so damn hot in here?"

Ah, but there is a difference here. As I heard it, God created
Adam, and he said "Yoicks its hot! I can't wait to invent air
conditioning." Shortly afterwards, God takes advantage of Adam
knocking himself out trying, and creates Eve. Her first words are
"Good God, it's cold in here, why not create some warm clothes and
central heat!"
And it has been a problem ever since.
-

The Garden of Eden was obviously not in Minnesota. Minnesota Mary
thinks 40's is wet sheet weather while Bubba Don about can't sleep
unless he's sweating a little.

I can relate to Sam McGee, oh yeah! Don't bury me in cold Fort
Snelling, please, take me to a roaring furnace!

http://www.youtube.com/watch?v=6lBkuz1TlVc

On Thu, 29 Oct 2009 23:54:40 -0700, pyotr filipivich
wrote:

Let the Record show that Gunner Asch on
or about Thu, 29 Oct 2009 21:52:22 -0700 did write/type or cause to
appear in rec.crafts.metalworking the following:
On Thu, 29 Oct 2009 20:39:27 -0700, pyotr filipivich
wrote:

Let the Record show that Lewis Hartswick on
or about Thu, 29 Oct 2009 06:53:05 -0600 did write/type or cause to
appear in rec.crafts.metalworking the following:
Stormin Mormon wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.

That is another one of those, " It Depends".
In this case on how long you will be gone.

Bingo. How long will you be gone, how low you set it, and how
fast does it take for the inside to cool down, and warm back up. If I
live where it is below freezing all the time, and the house is drafty
- I may shut the heat down more when I go out, because I can't afford
to heat all of Kansas! (OTOH, I might want to stand downwind of the
house and enjoy the heat I am paying for.)
If I have a snug warm house, that doesn't cool rapidly (lots of
thermal mass) then it doesn't matter _as much_.

When you come back, what are you going to do? Cooking dinner in
the oven is a good for reheating a house - or at least the kitchen.
B-)

And so it goes.
-

You in Kansas? My sister is single..and working for a Sherriffs
department in Kansas.....

Ooh, sounds interesting.

Alas, I have not lived in Kansas ... ack. Since before she was
born. There were only 48 states! No wait, that was after the start
of Camelot ... never mind. There were fifty. It just seems like it
was shortly after the glaciers receded, when the central sea dried
up...

Interested? Rather a hotty too as it happens.....

Not really my sister..but has been my "sister" for humm...20 yrs now. I
think she is 40..41ish.

If so..Ill turn you on to her face book page..and give you a strong
recommendation......

Alas, that is too far, or not far enough. I'm considering looking
into following the Boeing move.
-
pyotr filipivich
We will drink no whiskey before its nine.
It's eight fifty eight. Close enough!

Shrug...you really really dont know what you are missing. The woman can
keep you satisfied till the day you die..which would probably be a week
from next Thursday, given her sex drive.....and skills....

But then...


Gunner

"IMHO, some people here give Jeff far more attention than he deserves,
but obviously craves. The most appropriate response, and perhaps the
cruelest, IMO, is to simply killfile and ignore him. An alternative, if
you must, would be to post the same standard reply to his every post,
listing the manifold reasons why he ought to be ignored. Just my $0.02
worth."

On Oct 29, 2:30*pm, "Pete C." wrote:

An additional complication is occupancy, since for folks who are retired
or work from home, or a stay at home spouse, you loose half or more of
your theoretical savings period with the occupants not being away during
the day.-

When I am working the house cools off considerably at night and the
next day and I have to fire the wood stove hotter than its efficient
range to make up in the evening. When I am home all day I keep it
warmer with about the same amount of fuel.

OTOH if I fire it normally to recover there is an obvious and
considerable savings from allowing the temperature to drop for a day
or two, as during holiday trips or when measuring the cooling and
recovery rates.

Exact numbers are difficult, outdoor temperature changes constantly
and internally the living space and basement (where the stove is) act
like two loosely coupled thermal masses that cool at different rates.
I think the house loses between 2% and 3% of the in-out difference per
hour, substantially through infiltration which I don't want to reduce
below what it is now.

jsw

Don Foreman wrote:

Even the venerable Honeywell
"round" (T-87), which has been around for over 50 years, did and does
a surprisingly good job of this by virtue of it's anticipator --
which almost nobody outside of their engineering org really completely
understood.

Did the old standing pilot type furnaces tend to draw about the same current from one
model to another to turn the burner on? I always thought it was clever getting a bit of
heat via resistance to 'anticipate' when to turn off the burner.

Wes

On Thu, 29 Oct 2009 20:39:27 -0700, the infamous pyotr filipivich
scrawled the following:

Let the Record show that jeff_wisnia
on or about Thu, 29 Oct 2009 15:59:36 -0400 did write/type or cause to
appear in rec.crafts.metalworking the following:

Poll question:

How many guys here have wives who mistakenly think that when warming up
a cooled down house the rate of temperature change produced by a typical
home heating system will be faster if they shove the thermostat setting
all the way up to 90F than if they just move it to the appropriate setpoint.

Then of course, they forget to reset it when the place reaches a
comfortable temperature which some time later causes the man of the
house to snarl, "Why the hell is it so damn hot in here?"

Ah, but there is a difference here. As I heard it, God created
Adam, and he said "Yoicks its hot! I can't wait to invent air
conditioning." Shortly afterwards, God takes advantage of Adam
knocking himself out trying, and creates Eve. Her first words are
"Good God, it's cold in here, why not create some warm clothes and
central heat!"
And it has been a problem ever since.

Ayup. If any of my short list of girlfriends ever had control of the
thermostat, I could bop around the house naked without a care for
warmth. I was still hot. (No, not like that. Well, OK, that, too, but
I meant the "I-feel-like-I'm-in-Hawaii-on-the-beach" warm.)
It's a major reason I never got married. Common sense prevailed.

God, that was a meanass thing to do with male/female thermostats.


--
"Giving every man a vote has no more made men wise and free
than Christianity has made them good." --H. L. Mencken
---

The anticpators have an adjustment to match it to the furnace controls
in question. Standard install checkout procedure is to measure the
current, set the anticipator accordingly. That goes for the old standing
pilot models as well as the modern microprocessor controlled versions.

Wes wrote:
Don Foreman wrote:

Even the venerable Honeywell
"round" (T-87), which has been around for over 50 years, did and does
a surprisingly good job of this by virtue of it's anticipator --
which almost nobody outside of their engineering org really completely
understood.

Did the old standing pilot type furnaces tend to draw about the same current from one
model to another to turn the burner on? I always thought it was clever getting a bit of
heat via resistance to 'anticipate' when to turn off the burner.

Wes

80% are hardly known for "sucking every BTU".

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"RoyJ" wrote in message
m...
Echoing what Robert Nichols said:

I'm in the midst of optimizing a brand new, Bryant 80%
forced air, 2
stage, 110k Btu furnace. It sucks every BTU out of things
when running
in the low fire mode. On high fire it is just trying to get
you
comfortable enough to let it get back to the economy mode. I
doubt that
the difference is more than a few percent but I suspect it
is
measurable. If nothing else, the high fire mode requires the
high speed
fan and attendant increase in electrical use.

Granted that the 80% is less than the 92% units. But the **WEIGHTED**
average stack temperature is much less than the older versions. Every
short fire of the gas starts with the heat exchanger at ambient plus no
more than a couple of degrees. Stack doesn't even get warm to the touch
for half of the burn time in moderate weather. Hard to argue with that.

This also argues to the point that a temperature setback may not produce
the fuel savings one might expect.

Stormin Mormon wrote:
80% are hardly known for "sucking every BTU".

"Spehro Pefhany" wrote in message
...
On Thu, 29 Oct 2009 12:46:13 -0400, "Ed Huntress"
wrote:


"Bill Noble" wrote in message
...


"Ignoramus10802" wrote in message
...
On 2009-10-29, Pete C. wrote:

Ignoramus10802 wrote:

On 2009-10-29, Stormin Mormon
wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.


Imagine for a minute that you have to leave house for a month.

Would it be energy efficient to turn thermostat down? Of course, as
less heat will be produced for a whole month, with only a few minutes
to catch up.

The same applies to only one day.

i

It's far more complicated than that. Factors such as insulation / heat
loss, type of heating, multi-stage heating, electric backup heat on
heat
pumps, etc. all come into play in determining the away duration and
temp
reduction where savings begin, and in some cases (typically high
efficiency homes) it can require a multi day absence to see any
savings.

This is patently untrue.

I

Correct - whatever the net effect of insulation is, there is a net
negative heat flux from the house to the outside. The flux is
proportional to the temperature difference (the exact equation will
depend
on the radiation, convection and conduction components - radiation alone
is governed by the Stephan-Boltzman equation). The larger the
difference
the greater the flux. Averaged over any period of time, any time spent
with the thermostat set lower will yeild a lower internal temperature,
hence less heat flux. Whether that is enough to show up in your bill is
another question, but from a energy savings point of view, it is
incontestible.

The confounding issue, though, is the thermal mass of the house. That's
why
the DOE explanation says that the savings occur when the temperature
inside
the house has stabilized at the lower temperature.

When you shut off the furnace, the thermal mass of the inside of the house
is what's giving up heat to the outside. That's stored energy that came
from
the furnace heat. When you raise the temperature, you have to restore that
heat to the thermal mass. So with the furnace off and the temperature
inside
of the house dropping, you're losing stored heat. When you turn the
thermostat back on, you have to restore that lost heat, which will also
heat
up the atmosphere inside of the house (which is a very small portion of
the
total inside thermal mass).

That's what I read from their description, anyway, and it comports with
things I've read about it from other sources. There is no (theoretical)
net
gain or loss when the thermal mass is put through the cycle of cooling
down
and heating up. The savings occur when the temperature is reduced and
stabilized.

The furnace is supplying an average of so many BTU when it is running
(assuming the usual on/off type of furnace).

The house is losing so many BTU when it is at temperature T0 inside,
and the losses will always Be LESS when the temperaure is closer to
the outside temperature (assumed to be lower, of course).

Right. But the integrated savings over time will be around half (without
doing the math) of what one would have if the temperature of the house
actually dropped to its final temperature and stayed there for a long time.

In other words, if the house temp keeps dropping through the day to, say, 55
deg F, and then you set the thermostat back up to your normal temperature of
70, the whole cycle is one of loss from the thermal mass, then restoration
of the heat stored in the thermal mass. If your house is well-insulated, you
wind up with half of the savings (slightly more; it's a calculus problem and
the physics involve exponential decay, but averages will do for this
discussion) you'd have if you either left the thermostat set at 55 for a
couple of days, or if you had a lightly-built house with poor insulation and
the temperature dropped quickly when you turned down the thermostat.

According to DOE (and I've seen that information before), the savings
resulting from shutting off the furnace over a short period of time are
quite small, even on a per-hour basis, because the mean temperature of the
house is a lot higher than its temperature when you come home. They say
that, on the average, lowering the temperature 10 - 15 deg during the
workday, and lowering it again to some unspecified lower temp while you
sleep at night, saves, typically, 10% of your heating bill.

Just as an example, say you saved 10 cents/hour when the temperature of the
house remains at 55 over several days. But if you let it drop to 55 and then
immediately turn up the thermostat to 70, you only save 5 cents/hour. And
you have to wait for the house to heat up.

And here's a more telling example. Say the temperature outside is 50 deg,
your normal house temperature is 68 deg., and your house is well-insulated
and contains a lot of masonry, plaster walls, and other stuff with high
thermal mass. You shut off the thermostat completely when you leave for work
in the morning. When you come home, you turn it back up. The temperature in
the house is 60 at that time. I think everyone can see that the savings due
to the mean temperature differential is quite small. But many people are
going to think that, because the furnace was off all day, they're saving a
day's worth of fuel. Not.


When the house is cooling, the thermal mass is supplying part of the
heat to the outside.

If your furnace is *off*, the thermal mass is supplying 100% of the heat to
the outside.

When the house is heating up, the furnace is
supplying heat to warm the thermal mass, PLUS the heat which is being
lost to the outside.

Right.


The heat lost to the outside during the cooling *that is supplied by
the thermal mass* is made up for that part of the heat supplied by the
furnace to heat the house back to T0, so that part IS a wash.

Right.


What's missing is that for for every second the house is at a lower
temperature than T0, the heat loss to the outside is less, so even if
it cools down and immediately is heated up there will be an energy
saving.

Yes, but a much smaller one than most people would think, since their
furnace was off for a whole day.


If it was linear (which it isn't, but bear with me) then say the
outside temperature was 25F and the internal temperature was 75F.
The loss is k*(75-25) = k*50, where k is a constant. Now allow the
house to cool to 50F over an hour, then heat it back up again to 75F
over another hour. The heat loss to the outside during that time is
k*(62.5-25) = 37.5*k, which is 25% less (62.5F is the *average* inside
temperature over those two hours).

Right. So it's 25% less heat loss than you have at your normal temperature,
even though the temperature inside the house dropped to 50 deg. But most
houses don't lose heat that quickly. As a practical matter, you're only
gaining around half of what some people would expect by letting the
temperature drop to 50 deg and then heating the house back up.

Chances are the heat loss is
actually worse than linear (convection and radiation are worse, and
conduction is linear), so this should be conservative. Now if it's 25%
of 2/24 of a day, that's not very much (about 2% saving) but it is
going to be a saving.

Without getting into the math or the other routes for heat transfer, the 2%
is the point. You need to let the house stabilize at the lower temperature
before you're getting the kind of savings that most people think they should
get.


This all assumes that a house is decently insulated and that the thermal
mass of the house is substantial. Of course, the thermal differential
between the inside and outside temperatures are always at work, suggesting
that there is less heat loss with each degree of reduction of inside
temperature, as you say. But the DOE's reference to actual testing agrees
with the fact that, as soon as you turn the thermostat down, you begin
losing *stored* heat, and when you turn it back up, 100% of that lost heat
must be restored, regardless of actual thermal losses through the walls
and
ceiling.

Yes, that *part* of it is a wash.

wrote in message
...
On Oct 29, 8:22 pm, "Ed Huntress" wrote:

I've seen those studies for years, Don, starting with a book I read in the
'70s, titled something like _Low-cost, Energy-efficient Shelter_. What the
DOE says is widely known.

--
Ed Huntress

What the DOE says is widely known, but incorrect.

No, it's dead on, and based on a lot of actual experiments.

Don has explained
the problem correctly.

But he explained the wrong problem. He explained a theoretical
thermodynamics problem. The question is whether the savings would be worth
it if you only shut off the furnace for a relatively short time. And the
answer is, unless you live in a lightly-built and underinsulated trailer,
probably not.

Thermal mass and insulation determine the
thermal time constant, which affects how much saving results. But
has no effect on whether there is a savings.

Again, you're talking about a vacuum-bottle experiment. The question is
whether the savings are worth coming back to a 50 deg house.


As Pete C. points out there are some heating systems that change
efficiency depending on the demand. Heat pumps are one case.

Approximately 8% of homes.

Another
case is modulating furnaces. These will be less efficient at higher
loads. But the common furnace located in a non heated area, will be
somewhat more efficient as the furnace will run for a longer time
before shutting off and loosing heat to the unheated area.

All of this is very nice for armchair philosophizing, Dan, but you have to
know the actual *values* involved in the practical problem to know whether
they're significant issues, in terms of your monthly heating bill. DOE has
done the work, and I've shown what their actual experiments show. The
savings are quite small in a typical house unless you leave the furnace off,
or the temperature set low, for a long enough period for the STABILIZED
temperature to be maintained for a significant portion of the total cycle.

Thermal mass works against you, by extending the ramping-down and -up
portions of the cycle. Likewise, insulation.

--
Ed Huntress

"David Billington" wrote in message
...
Ed Huntress wrote:
"jeff_wisnia" wrote in message
eonecommunications...

Ed Huntress wrote:


"Ignoramus10802" wrote in message
...


On 2009-10-29, ATP* wrote:


True. Yet I still hear this type of "reasoning" all the time. Should
be a
simple concept even for the technically challenged, for example,
people who
argued here that you can compress air and allow it to expand (while
doing no
useful work) with no loss of energy.

That would be almost possible if compressing and expanding was done
very quickly, before compressed air cools.

i

But it has to be done *awfully* quickly. That's why there's a minimum
cylinder size for diesel engines -- something like 300 cc. Below 3,000
rpm or so, the compressed air cools too quickly to ignite the fuel. And
heat transfer gets worse as compression goes up.


That statement may not be entirely correct, Ed.

Remembering waaaay back to my childhood playing around with control line
model aircraft. before the glow plug engine was developed we had but two
choices, conventional spark plug engines and diesel engines.


g I had one of those. They weren't really diesels (technically, they're
"homogeneous charge, compression-ignition engines), but that isn't the
issue, because they ignite from compression, the same as a true diesel.
The issue is that they use ether for fuel, or an ether-diesel mix in the
larger ones, and ether has a cetane rating of 86. Diesel fuel runs around
40 - 45 cetane. Those little engines can't produce enough heat from
compression to ignite diesel fuel.


The diesels were never very popular, but they are still being made for
thos who want to add a bit of "authenticity" to replicas of vintage
model aircraft. Those are surely far below 300 cc, but the fuel they
burn may not be quite the same as what cars and trucks use. G

http://www.eifflaender.com/enginepics.htm

I also remember my not terribly successful efforts at flying RC models
back then. My ham ticket let me do that legally on 28 Mhz (the 10 meter
ham band) using a one tube receiver in the plane which triggered a
rubber band energized "escapement" that moved a combination
rudder-stabilizer at the rear of the plane.


A tail-wagger. I built one of those, a Cessna Birddog from a kit, with an
.049 Babe Bee engine. I used a salvaged CB walkie-talkie for a
transmitter and a homebrew superregen receiver. The signal was CW. I made
the escapement from a tin can, with bits of HSS hacksaw blade soldered
onto the tips of the arms. It flew pretty well, but I was not much of a
pilot. Fortunately, if you just tossed the transmitter aside, it would
land by itself.


How the heck I just remembered that the tube used in those receivers was
an RK61, a gas filled triode, I'll never understand.


For the same reason that I remember that my first homebrew regen
receiver, a battery-powered rig that I built in 1957, used a 1T4. Our
memories of old stuff tend to hang in there while we forget what we had
for breakfast. d8-)


http://tubedata.milbert.com/sheets/138/r/RK61.pdf

Thaks for the mammaries though.

Jeff


sigh That's most of what I'm good for these days. Sometimes I feel like
an antique. d8-(


A small diesel here
http://www.model-engineer.co.uk/albu...=6778&p=123122 ,
about 28cc, not sure about the relation of lamp oil to pump diesel but it
sounds less volatile than the small "diesel" aircraft engines I used on
occasions which were a blend of ether, caster oil and amyl nitrate. Last
time I used one was about 1981 and on returning to the US from the UK I
asked my chemistry teacher about getting some ether to blend my own and
she almost had a fit, then gave me a lecture about the dangerous nature of
ether. Didn't know then that engine start spray is mostly ether and have
seen a thread elsewhere where a chap detailed using it to refill a
capillary temperature gauge, Lucas IIRC.

"Lamp oil" covers a lot of different products, but there are references in
the literature to using it as a cetane booster for diesels. Unconfirmed
references say that its cetane rating can be as high as 70.

The point is that small engines lose much more heat to the cylinder walls,
cylinder head, and piston crown, because of the relationship between volume
and surface area in a cylinder. When you get below 300 cc or so per
cylinder, conventional diesel fuel will either not run smoothly or reliably,
or not at all. The heat loss of the compressed air is too great and the
resulting temperature is too low to ignite regular diesel fuel.

There are some small specialty engines that use spark ignition or a glowplug
to start and heat up the engine, which is then switched to compression
ignition. I don't know how well they run but it all depends on how well they
can keep the temperature up inside of the cylinder. I would guess that their
efficiency is low, too, because of quenching against the cylinder walls
while the engine is running.

I was not talking about those, or about the models that run on high-cetane
fuels, which typically are too expensive, or, as you say, too dangerous to
use as a primary fuel.

You can buy ether in the US. I had a can of it for years that I used to
start a balky, clapped-out lawnmower.

--
Ed Huntress

"Don Foreman" wrote in message
...
On Thu, 29 Oct 2009 16:22:30 -0400, "Ed Huntress"
wrote:



The point is that what you're talking about is insignificant in most
homes.
That's what the DOE statement is all about: cycling of the heat mass
overwhelms the effect of the insulation, until the temperature is reduced
and stabilized for a while. Otherwise, all you're doing is cycling the
heat
retention of the thermal mass, with relatively much less actual savings as
the temperature drops in the house.

Furnaces cycle anyway, and often at about the same cyclic rate almost
independent of temperature or heat load. To meet higher heat load
(higher indoor temp or lower outdoor temp) they just have a higher
percentage of "on" time each cycle. Even the venerable Honeywell
"round" (T-87), which has been around for over 50 years, did and does
a surprisingly good job of this by virtue of it's anticipator --
which almost nobody outside of their engineering org really completely
understood.


Whether or not the savings on the energy bill is noticable is another
question depending on how much the setback was for how long.

I wonder how much the DOE spent on a study to address what would be an
easy test question in thermodynamics 101.

Probably enough to know that you learned your thermodynamics with a
calculator and a vacuum jar, rather than a house. g

They'd be wrong about that too. During my 33 years with Honeywell I
worked with engineers and scientists worldwide,including those from
their homes and buildings divisions.

I was invited by DOE just last week to serve as a technical reviewer
for buildings programs. (I'm not going to do it.) I was also on the
Technical Advisory Board for DOE's Brookhaven National Labs back in
the late 90's.

I've seen those studies for years, Don, starting with a book I read in the
'70s, titled something like _Low-cost, Energy-efficient Shelter_. What the
DOE says is widely known.

It is indeed, and it's known in the technical community to be wrong.

I've lost track of what you're saying is "right" or "wrong." It's a fact
that your savings are much lower than many would expect when you simply let
the temperature drop to some particular temperature and then start heating
the house up again, as you would if you turned the furnace off when you left
in the morning and then turned it back on when you got home.

It's another fact that the savings become significant when the lowest inside
temperature prevails for most of the cycle time, whether it's because the
house has reached outside temperature or because you simply set the
thermostat down to some temperature above outside temperature.

Physics was my best subject, too, Don. I'm aware of the physics involved.
There even was a time when I could do the equations without batting an eye.
Now, I let my thumbs rule. d8-) The question concerns whether the saving is
enough to make it worthwhile, not whether you can calculate the exponential
decay and the integrated temperature differential and show some numerical
value for the savings. Again, it's much less than most people expect.

--
Ed Huntress

"Don Foreman" wrote in message
...
On Thu, 29 Oct 2009 12:46:13 -0400, "Ed Huntress"
wrote:


"Bill Noble" wrote in message
...


"Ignoramus10802" wrote in message
...
On 2009-10-29, Pete C. wrote:

Ignoramus10802 wrote:

On 2009-10-29, Stormin Mormon
wrote:
Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.


Imagine for a minute that you have to leave house for a month.

Would it be energy efficient to turn thermostat down? Of course, as
less heat will be produced for a whole month, with only a few minutes
to catch up.

The same applies to only one day.

i

It's far more complicated than that. Factors such as insulation / heat
loss, type of heating, multi-stage heating, electric backup heat on
heat
pumps, etc. all come into play in determining the away duration and
temp
reduction where savings begin, and in some cases (typically high
efficiency homes) it can require a multi day absence to see any
savings.

This is patently untrue.

I

Correct - whatever the net effect of insulation is, there is a net
negative heat flux from the house to the outside. The flux is
proportional to the temperature difference (the exact equation will
depend
on the radiation, convection and conduction components - radiation alone
is governed by the Stephan-Boltzman equation). The larger the
difference
the greater the flux. Averaged over any period of time, any time spent
with the thermostat set lower will yeild a lower internal temperature,
hence less heat flux. Whether that is enough to show up in your bill is
another question, but from a energy savings point of view, it is
incontestible.

The confounding issue, though, is the thermal mass of the house. That's
why
the DOE explanation says that the savings occur when the temperature
inside
the house has stabilized at the lower temperature.

When you shut off the furnace, the thermal mass of the inside of the house
is what's giving up heat to the outside. That's stored energy that came
from
the furnace heat. When you raise the temperature, you have to restore that
heat to the thermal mass. So with the furnace off and the temperature
inside
of the house dropping, you're losing stored heat. When you turn the
thermostat back on, you have to restore that lost heat, which will also
heat
up the atmosphere inside of the house (which is a very small portion of
the
total inside thermal mass).

Imagine a bucket with a pinhole leak near the bottom. Let's consider
the level of the water in the bucket as analogous to temperature in an
insulated enclosure. The diameter of the bucket determines the mass of
water needed to reach a given level. It's a valid analogy because
temperature is a measure of thermal potential, water height determines
pressure pushing water out the pinhole leak. Water leak rate is qty
of water per unit time, heat leak rate is qty of heat energy (Joules,
BTU, etc) per unit time.

Let's rig a little toilet-valve arrangement to maintain the level
except that it will have hysteresis: it will click on when water is
below a certain level and refil the bucket until the water rises some
incremental amount whereupon it will click off. Refill will stop and
the level will gradually go down because of the pinhole leak. How
long it takes to go down depends on the size of the leak (insulation)
and the diameter of the bucket (thermal mass).

I hope it's apparent that if the leakrate is 1 gallon per minute then
the average replenishment rate must also be 1 gallon per minute. If
it's less, the level will recede, if it's more the level will rise.

If we now lower the height of the toilet valve, there will be no
influx until the bucket leaks down to that level. If we then raise
the valve, the valve will stay open until the water has risen to that
level. But the average long-term water consumption will still be the
leakrate.

Note that this is true regardless of the diameter of the bucket.

It is true that both leak rates depend on potential (depth or
temperature difference) so differential equations are required to
express them correctly. This does not change the fact that what goes
in must equal what goes out long term if the long-term average
temperature is constant over several cycles of moving the setpoint up
and down.

As I said, I'm aware of the physics, Don. But the questions, which have gone
all around the barn, are about whether it's worth it. And the answer is that
it's much more worthwhile if your periods of turning the furnace off (or the
thermostat 'way down) are quite long.

DOE addressed the question accurately: if you have two periods of reduced
heat per day -- the time you're at work and the time you're sleeping at
night -- you'll typically save 10%. That's a figure that's been tested and
reported for decades.

Most people think that shutting off their furnace for four hours should save
four hours worth of fuel. It doesn't. If the temperature keeps dropping
until you turn the furnace back on, you save the equivalent of roughly two
hours of fuel, not four hours.

And another way to look at it is whether shutting off the furnace 12 times
per day, for an hour each time, is equivalent in terms of savings to
shutting it off one time for 12 hours. The answer is, no; it probably is on
the order of 50% of the savings you get by shutting it off once for 12
hours.

The DOE's tests specifically addressed some common misconceptions. Both in
terms of the misconceptions over the physics and in terms of misconceptions
about actual savings, they were quite right.

--
Ed Huntress

Pete C. wrote:
jeff_wisnia wrote:
Stormin Mormon wrote:

Please forgive me while I troll for a moment.....

Is it energy saving to turn the thermostat down, when
leaving the house? I mean, the furnace has to run to catch
up when I get home. I have a way of looking at the matter.
I'll explain my point of view after the argument is
underway.

OK, Stormin, let's have your point of view now.

Poll question:

How many guys here have wives who mistakenly think that when warming up
a cooled down house the rate of temperature change produced by a typical
home heating system will be faster if they shove the thermostat setting
all the way up to 90F than if they just move it to the appropriate setpoint.

Then of course, they forget to reset it when the place reaches a
comfortable temperature which some time later causes the man of the
house to snarl, "Why the hell is it so damn hot in here?"

And visa versa for A/C of course.

It can't just only happen to me. G

Jeff

PS, I realize there may be some HVAC systems (and some wives too of
course) which don't conform to the above scenario, but they sure aren't
in the majority around here.

One of my tests for a potential girlfriend is to have here explain how a
thermostat operates. Few pass this test of course, but it sure saves a
lot of time and money.

Hers or yours? ;-)

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:

On Fri, 30 Oct 2009 13:17:41 -0400, "Ed Huntress"
wrote:



As I said, I'm aware of the physics, Don. But the questions, which have gone
all around the barn, are about whether it's worth it. And the answer is that
it's much more worthwhile if your periods of turning the furnace off (or the
thermostat 'way down) are quite long.

DOE addressed the question accurately: if you have two periods of reduced
heat per day -- the time you're at work and the time you're sleeping at
night -- you'll typically save 10%. That's a figure that's been tested and
reported for decades.

That's as good as any generalization. Savings vary a lot with how
much the homeowner sets back and for what percentage of the time. The
length of each period is only relevant if it is small or comparable to
the time constant of the enclosure. If the period is short enough
that the space can only cool 5 degrees, then lowering the setpoint
more than that has no effect or benefit.

But the assertion about not saving anything until the house is
stabilized at the lower temp is wrong, and the stuff about cycling
thermal mass requiring net energy is also wrong.

When these studies were done, 10% savings was far from trivial.
Houses are *much* more energy-efficient now than they were 30 years
ago.

"Don Foreman" wrote in message
news
On Fri, 30 Oct 2009 13:17:41 -0400, "Ed Huntress"
wrote:



As I said, I'm aware of the physics, Don. But the questions, which have
gone
all around the barn, are about whether it's worth it. And the answer is
that
it's much more worthwhile if your periods of turning the furnace off (or
the
thermostat 'way down) are quite long.

DOE addressed the question accurately: if you have two periods of reduced
heat per day -- the time you're at work and the time you're sleeping at
night -- you'll typically save 10%. That's a figure that's been tested and
reported for decades.

That's as good as any generalization. Savings vary a lot with how
much the homeowner sets back and for what percentage of the time. The
length of each period is only relevant if it is small or comparable to
the time constant of the enclosure. If the period is short enough
that the space can only cool 5 degrees, then lowering the setpoint
more than that has no effect or benefit.

But the assertion about not saving anything until the house is
stabilized at the lower temp is wrong...

I should have said "anything significant." Somehow significance stuck in my
mind throughout that discussion.

...and the stuff about cycling
thermal mass requiring net energy is also wrong.

I don't know who said that, but it wasn't me. Or if I did, then I misspoke.

Just to make sure we agree he If you read what DOE actually says, it's
perfectly accurate. They don't get into thermal masses or hypothetical
examples. They're talking about real savings, based both on theory and, more
importantly, on real tests run over a period of decades.


When these studies were done, 10% savings was far from trivial.
Houses are *much* more energy-efficient now than they were 30 years
ago.

--
Ed Huntress

On Fri, 30 Oct 2009 14:58:11 -0400, "Ed Huntress"
wrote:


"Don Foreman" wrote in message
news
On Fri, 30 Oct 2009 13:17:41 -0400, "Ed Huntress"
wrote:



As I said, I'm aware of the physics, Don. But the questions, which have
gone
all around the barn, are about whether it's worth it. And the answer is
that
it's much more worthwhile if your periods of turning the furnace off (or
the
thermostat 'way down) are quite long.

DOE addressed the question accurately: if you have two periods of reduced
heat per day -- the time you're at work and the time you're sleeping at
night -- you'll typically save 10%. That's a figure that's been tested and
reported for decades.

That's as good as any generalization. Savings vary a lot with how
much the homeowner sets back and for what percentage of the time. The
length of each period is only relevant if it is small or comparable to
the time constant of the enclosure. If the period is short enough
that the space can only cool 5 degrees, then lowering the setpoint
more than that has no effect or benefit.

But the assertion about not saving anything until the house is
stabilized at the lower temp is wrong...

I should have said "anything significant." Somehow significance stuck in my
mind throughout that discussion.

...and the stuff about cycling
thermal mass requiring net energy is also wrong.

I don't know who said that, but it wasn't me. Or if I did, then I misspoke.

Just to make sure we agree he If you read what DOE actually says, it's
perfectly accurate. They don't get into thermal masses or hypothetical
examples. They're talking about real savings, based both on theory and, more
importantly, on real tests run over a period of decades.

I don't know which DOE study you refer to here since there were
several, but I have no quarrel with findings based on actual data.
Honeywell did their own studies with similar findings.

Precis of findings:
How much does a setback stat save? It depends.
Are the savings significant? Maybe.
10% of not much is hardly any.
10% of a whole bunch is some.
Buy a Honeywell Chronotherm. Your family deserves the best.

Some gov't studies are almost laughable when they wander off into the
weeds trying to offer an impressive technical explanation of what the
data says and why, which more often is really the writer's attempt to
impress by verbose technobabble obfuscation. It's well known in
contract research labs that the gov't wants big thick reports for
their research buck. Hell, the proposals alone sometimes look like
phonebooks. It's widely suspected that nobody actually reads these
reports, they just weigh them and assign a grade.

Makes me think of a notorious DOH or OSHA study that spent 3/4 mil
finding that pig**** is slick. (Safety issues in pig farms or
something like that).

"Don Foreman" wrote in message
...
On Fri, 30 Oct 2009 14:58:11 -0400, "Ed Huntress"
wrote:


"Don Foreman" wrote in message
news
On Fri, 30 Oct 2009 13:17:41 -0400, "Ed Huntress"
wrote:



As I said, I'm aware of the physics, Don. But the questions, which have
gone
all around the barn, are about whether it's worth it. And the answer is
that
it's much more worthwhile if your periods of turning the furnace off (or
the
thermostat 'way down) are quite long.

DOE addressed the question accurately: if you have two periods of
reduced
heat per day -- the time you're at work and the time you're sleeping at
night -- you'll typically save 10%. That's a figure that's been tested
and
reported for decades.

That's as good as any generalization. Savings vary a lot with how
much the homeowner sets back and for what percentage of the time. The
length of each period is only relevant if it is small or comparable to
the time constant of the enclosure. If the period is short enough
that the space can only cool 5 degrees, then lowering the setpoint
more than that has no effect or benefit.

But the assertion about not saving anything until the house is
stabilized at the lower temp is wrong...

I should have said "anything significant." Somehow significance stuck in
my
mind throughout that discussion.

...and the stuff about cycling
thermal mass requiring net energy is also wrong.

I don't know who said that, but it wasn't me. Or if I did, then I
misspoke.

Just to make sure we agree he If you read what DOE actually says, it's
perfectly accurate. They don't get into thermal masses or hypothetical
examples. They're talking about real savings, based both on theory and,
more
importantly, on real tests run over a period of decades.

I don't know which DOE study you refer to here since there were
several, but I have no quarrel with findings based on actual data.
Honeywell did their own studies with similar findings.

Precis of findings:
How much does a setback stat save? It depends.
Are the savings significant? Maybe.
10% of not much is hardly any.
10% of a whole bunch is some.
Buy a Honeywell Chronotherm. Your family deserves the best.

Some gov't studies are almost laughable when they wander off into the
weeds trying to offer an impressive technical explanation of what the
data says and why, which more often is really the writer's attempt to
impress by verbose technobabble obfuscation. It's well known in
contract research labs that the gov't wants big thick reports for
their research buck. Hell, the proposals alone sometimes look like
phonebooks. It's widely suspected that nobody actually reads these
reports, they just weigh them and assign a grade.

Makes me think of a notorious DOH or OSHA study that spent 3/4 mil
finding that pig**** is slick. (Safety issues in pig farms or
something like that).


That probably was a report about Chicago's Grant Park in 1968. g

--
Ed Huntress

On Oct 30, 4:31*pm, "Ed Huntress" wrote:


No, it's dead on, and based on a lot of actual experiments.

Don has explained
the problem correctly.

But he explained the wrong problem. He explained a theoretical
thermodynamics problem. The question is whether the savings would be worth
it if you only shut off the furnace for a relatively short time. And the
answer is, unless you live in a lightly-built and underinsulated trailer,
probably not.

Thermal mass and insulation determine the
thermal time constant, *which affects how much saving results. *But
has no effect on whether there is a savings.

Again, you're talking about a vacuum-bottle experiment. The question is
whether the savings are worth coming back to a 50 deg house.


Ed Huntress

You need to improve your reading comprehension. The question was

"Is it energy saving to turn the thermostat down, when
leaving the house?"

It was not whether the savings were worthwhile. Or whether a 50
degree house is comfortable. Incidentally the problem can not be
accurately described by lump constants. The electrical analogy is a
transmission line, not a capacitor.

Dan

wrote in message
...
On Oct 30, 4:31 pm, "Ed Huntress" wrote:


No, it's dead on, and based on a lot of actual experiments.

Don has explained
the problem correctly.

But he explained the wrong problem. He explained a theoretical
thermodynamics problem. The question is whether the savings would be worth
it if you only shut off the furnace for a relatively short time. And the
answer is, unless you live in a lightly-built and underinsulated trailer,
probably not.

Thermal mass and insulation determine the
thermal time constant, which affects how much saving results. But
has no effect on whether there is a savings.

Again, you're talking about a vacuum-bottle experiment. The question is
whether the savings are worth coming back to a 50 deg house.


Ed Huntress

You need to improve your reading comprehension. The question was

"Is it energy saving to turn the thermostat down, when
leaving the house?"

It was not whether the savings were worthwhile.

Right. So the question was not whether it was worth doing, but whether one
could calculate some reduction in total joules of energy by working it out
with a calculator.

Save your pedantry, Dan. It's not illuminating. It's just annoying.

--
Ed Huntress

On Oct 30, 10:06*pm, "Ed Huntress" wrote:

Right. So the question was not whether it was worth doing, but whether one
could calculate some reduction in total joules of energy by working it out
with a calculator.

Save your pedantry, Dan. It's not illuminating. It's just annoying.

--
Ed Huntress

Well everyone else was answering the question that Stormy asked. You
are the only one that decided to ignore the question and answer what
you wanted to talk about. Which explains why you could not understand
why so many intelligent people disagreed with you. And to be
pedantic, the question was not about calculating the amount of
reduction. There are way too many variables to do that.

Dan

wrote in message
...
On Oct 30, 10:06 pm, "Ed Huntress" wrote:

Right. So the question was not whether it was worth doing, but whether one
could calculate some reduction in total joules of energy by working it out
with a calculator.

Save your pedantry, Dan. It's not illuminating. It's just annoying.

--
Ed Huntress

Well everyone else was answering the question that Stormy asked. You
are the only one that decided to ignore the question and answer what
you wanted to talk about. Which explains why you could not understand
why so many intelligent people disagreed with you. And to be
pedantic, the question was not about calculating the amount of
reduction. There are way too many variables to do that.

Pfffht. Go correct a kid's homework or something.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"Don Foreman" wrote in message
...
On Thu, 29 Oct 2009 16:22:30 -0400, "Ed Huntress"
wrote:



The point is that what you're talking about is insignificant in most
homes.
That's what the DOE statement is all about: cycling of the heat mass
overwhelms the effect of the insulation, until the temperature is reduced
and stabilized for a while. Otherwise, all you're doing is cycling the
heat
retention of the thermal mass, with relatively much less actual savings
as
the temperature drops in the house.

Furnaces cycle anyway, and often at about the same cyclic rate almost
independent of temperature or heat load. To meet higher heat load
(higher indoor temp or lower outdoor temp) they just have a higher
percentage of "on" time each cycle. Even the venerable Honeywell
"round" (T-87), which has been around for over 50 years, did and does
a surprisingly good job of this by virtue of it's anticipator --
which almost nobody outside of their engineering org really completely
understood.


Whether or not the savings on the energy bill is noticable is another
question depending on how much the setback was for how long.

I wonder how much the DOE spent on a study to address what would be an
easy test question in thermodynamics 101.

Probably enough to know that you learned your thermodynamics with a
calculator and a vacuum jar, rather than a house. g

They'd be wrong about that too. During my 33 years with Honeywell I
worked with engineers and scientists worldwide,including those from
their homes and buildings divisions.

I was invited by DOE just last week to serve as a technical reviewer
for buildings programs. (I'm not going to do it.) I was also on the
Technical Advisory Board for DOE's Brookhaven National Labs back in
the late 90's.

I've seen those studies for years, Don, starting with a book I read in
the
'70s, titled something like _Low-cost, Energy-efficient Shelter_. What
the
DOE says is widely known.

It is indeed, and it's known in the technical community to be wrong.

I've lost track of what you're saying is "right" or "wrong." It's a fact
that your savings are much lower than many would expect when you simply
let the temperature drop to some particular temperature and then start
heating the house up again, as you would if you turned the furnace off
when you left in the morning and then turned it back on when you got home.

It's another fact that the savings become significant when the lowest
inside temperature prevails for most of the cycle time, whether it's
because the house has reached outside temperature or because you simply
set the thermostat down to some temperature above outside temperature.

Physics was my best subject, too, Don. I'm aware of the physics involved.
There even was a time when I could do the equations without batting an
eye. Now, I let my thumbs rule. d8-) The question concerns whether the
saving is enough to make it worthwhile, not whether you can calculate the
exponential decay and the integrated temperature differential and show
some numerical value for the savings. Again, it's much less than most
people expect.

--
Ed Huntress
The misconception is that the heating plant will have to "work harder" to
catch up, leading some people to believe that a setback actually wastes
energy. Except in the specialized case of a heat pump on the verge of
electric resistance operation, that is not the case. Whether it is "worth
it" or not is another question. In a leaky building it definitely is.