Abby Normal wrote

When it is sized to the load the problem is it would only shut off for
an hour or two as the house cooled, then it would run steady until
after the sun came up to catch up. No real point in setting back.

That is just plain wrong. The whole point of a set back is that
less is pumped at the setback temp because the losses are lower.
How much lower depends on how well insulated the house is.

The only way set back works with a heat pump is if it is grossly oversized.

Wrong again.

All that accomplishes is set back without auxiliary heat.
It would short cycle inefficiently except for when it was
trying to recover from a set back.

Not if you one of the systems sized so that doesnt happen.

In an environment with an ambient dewpoint above 60F there will
be problems with a grossly oversized system in cooling mode.

Again, not if you have more than one system.

Abby Normal pontificates:

The only way set back works with a heat pump is if it is grossly
oversized. All that accomplishes is set back without auxiliary heat. It
would short cycle inefficiently except for when it was trying to
recover from a set back.

I disagree.

Nick

That was honest of you.

"Abby Normal" wrote in message
oups.com...
I only sold ground source in areas where gas was not
available.
Compared to propane, oil and straight electric they
are viable.

I had an opportunity to sell one in a gas area and it
would have saved
about $100 per year over high-efficiency gas, but
talked the customer
out of it as he would have spent perhaps 6 grand more
than the gas
furnace with central ac.


John P.. Bengi wrote:
I also know of two ground source units that have
bit
the dust and were never replaced due to costs
compared
to gas here. I have heard longer life with the
ground
source units though. The air source units had too
many
freeze up problems with rainy freezing weather then
the
"defrost" cycle had to be brought in and the unit
was
never big enough to handle the BTU load anyway so
the
backup was cutting in from timte to time.


"Abby Normal" wrote in
message

oups.com...
Air source were useless in NW Ontario, ground
source
worked.
John P.. Bengi wrote:
Slowly but surely, I guess. I become more glad
with
each year I didn't indulge.

With NG 1/3 of the price of electricity here,
the
reliability very poor, and a complete backup
system
required anyway, I doubt they will be selling
many
of
them anymore.

Sounded good in the 80s though.

"Abby Normal" wrote in
message


ups.com...
Air source getting yanked out of Southern
Ontario?

Abby Normal pontificates:



The only way set back works with a heat pump is if it is grossly
oversized. All that accomplishes is set back without auxiliary heat. It
would short cycle inefficiently except for when it was trying to
recover from a set back.


I disagree.

Nick


You disagree with almost everything Nick. Have you EVER installed ANY
heating or cooling equipment? Have you EVER installed a heat pump? Do
you have test equipment and data loggers to measure the performance?
Do you have any PRACTICAL experience? Or do you just like to disagree?
You obviously have a brain, it is a shame you don't do something more
constructive with it.

Stretch

for day:= Monday to Sunday
for post:= first to last
if answering_mode then
if person = respected then
post_snipe
else
if rnd()0.5 then
ad_hominem_attack()
else
declare_previously_resolved_by_self
endif
endif
else
with theory_confusion
post_basic_babble()
end with
endif
next post
next day

Stretch wrote:

Abby Normal pontificates:

The only way set back works with a heat pump is if it is grossly
oversized. All that accomplishes is set back without auxiliary heat. It
would short cycle inefficiently except for when it was trying to
recover from a set back.

I disagree.

You disagree with almost everything Nick.

I disagree.

Have you EVER installed ANY heating or cooling equipment? Have you EVER
installed a heat pump? Do you have test equipment and data loggers to
measure the performance? Do you have any PRACTICAL experience?

Yes. No. Yes. Yes. Why? Need some help? :-) HVAC criminals are not Gods.
Their assertions demand no more than counterassertions.

Now why do we need a 2-speed compressor vs a 2-speed fan?

Nick

Nick,

A two speed compressor gives two capacities. Typically low speed
compressor will give you 67% of the capacity that you get on high speed
compressor operation. A two speed fan just changes the SHR without
changing the capacity much. Youi may get a 5% variance in capacity by
changing just the blower speed. Note that when you change the
compressor speed you must change the blower speed as well. The
compressor will usually run at 1725 RPM on low speed and 3450 RPM on
high speed. Normally the indoor unit has a variable speed blower so
the air flow can change about 2 to 1. A standard multi tap motor has
trouble doing that. The ducts should be sized for high speed
operation.

Some systems use two swparate compressors (Trane). You have to be
careful of your refrigerant line sizing so you get good oil return to
the compressor(s).

Stretch

Abby Normal wrote:
With heat pumps and or high thermal mass buildings, set back is not

always a good scheme. If you set it back during the day, such as when

occupants go to work, think about having the space back up to

temperature before the sun sets.

Hey Ronnie, get er up to temp before the sun sets.

Abby Normal wrote
Abby Normal wrote

With heat pumps and or high thermal mass buildings, set back
is not always a good scheme. If you set it back during the day,
such as when occupants go to work, think about having the
space back up to temperature before the sun sets.

Hey Ronnie, get er up to temp before the sun sets.

Pity that was clearly about a setback during the
day, not the overnight actually being discussed.

Pity you also pig ignorantly claimed

Setback has a value, just not with heat pumps.

Cant even manage a consistent line in pig ignorant bull****.

Stretch wrote:

A two speed compressor gives two capacities. Typically low speed
compressor will give you 67% of the capacity that you get on high speed
compressor operation. A two speed fan just changes the SHR without
changing the capacity much. Youi may get a 5% variance in capacity by
changing just the blower speed... Normally the indoor unit has a variable
speed blower so the air flow can change about 2 to 1. A standard multi tap
motor has trouble doing that.

Why do we need a 2-speed compressor? Abby suggests a high capacity heat pump
for winter setbacks will do poorly for summer AC because it will inefficiently
short cycle and won't dehumidify well. It seems to me that it can dehumidify
well with less indoor airflow and a freezestat that turns off the compressor
while the blower keeps running. What are the numbers for this "short cycling?"

When do we have to worry about premature wearout or inefficiency resulting
from too many starts? If a 3 ton heat pump runs 100% of the time at the winter
design temp, can it do 1 ton of AC in summertime with less indoor airflow?
Maybe the answer to this question depends on thermal mass. If the AC runs for
10 minutes out of every half-hour that might be fine. If it has to run for
1 minute every 3 minutes that might be no good. Is there some way to add
thermal mass to the indoor coil? Do we need to worry about short cycling
on mild winter days?

Nick

Nick,
The next time you see an AC or heat pump, Use one of your data loggers
to measure the temperature drop across the indoor coil. The indoor
coil will take 10 to 15 minutes to reach max coldness. The colder the
ID coil gets, the farther below dew point it will be and the more
moisture it will take out. With a less cold coil, while it will cool
the house, it will not dehumidify well. That is why you want to size
it properly. The ID coil does not get cold instantly. A properly
sized unit will run longer and dehumidify better without losing
effeicieny. By the way, when they test efficiency, they run the
systems for an hour before they do the testing. Systems do not read
max efficiency till they have run an hour. Gas furnaces are the same
way.

If you just lower the air flow, if you go below 350 CFM per ton, your
system will loose capacity, while using about the same electricity.
Again, use your data loggers to measure capacity and power consumption.
So the efficiency goes to hell. If you recall, the original idea of
setback was to save money on electricity. Now we are talking about
extreeme efforts to make an oversized system work at all, running the
electric bills out of sight!

Sounds like you are all going in the wrong dirrection.

wrote:
Stretch wrote:

A two speed compressor gives two capacities. Typically low speed
compressor will give you 67% of the capacity that you get on high speed
compressor operation. A two speed fan just changes the SHR without
changing the capacity much. Youi may get a 5% variance in capacity by
changing just the blower speed... Normally the indoor unit has a variable
speed blower so the air flow can change about 2 to 1. A standard multi tap
motor has trouble doing that.

Why do we need a 2-speed compressor? Abby suggests a high capacity heat pump
for winter setbacks will do poorly for summer AC because it will inefficiently
short cycle and won't dehumidify well. It seems to me that it can dehumidify
well with less indoor airflow and a freezestat that turns off the compressor
while the blower keeps running. What are the numbers for this "short cycling?"

In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated
resulting in elevated indoor RH. 3 steps forward and 2 steps back.

It is even worse with a draw through air handler installed in a
horizontal position, the drain pans have a side connection. This means
that there is approximately an 1/8 of an inch of standing water tht
does not drain. So along with re-evaporating the moisture that did not
drain off of the coil, the constant fan makes the air handler into and
adibiatic saturator as it dries out the drain pan too.

Ballpark figure, constant fan will keep the indoor RH about 10% higher
than fan in "auto" mode. Hard concept to believe in the north but
perhaps search and see what Building Science or the Florida Solar
Center has to say on this matter.

When do we have to worry about premature wearout or inefficiency resulting
from too many starts? If a 3 ton heat pump runs 100% of the time at the winter
design temp, can it do 1 ton of AC in summertime with less indoor airflow?
Maybe the answer to this question depends on thermal mass. If the AC runs for
10 minutes out of every half-hour that might be fine. If it has to run for
1 minute every 3 minutes that might be no good. Is there some way to add
thermal mass to the indoor coil? Do we need to worry about short cycling
on mild winter days?

Well you are the electrical engineer by training so I would assume that
you realize that motors are aged every time they are started.

In an environment where in the summer the outdoor dewpoint will not be
that high then you could size a heat pump (most likely a ground source
heat pump) to the heating load and be grossly oversized for cooling.
But with a relatively low ambient dewpoint you would not end up with
the high indoor RH.

Typically a heat pump is sized with cooling in mind to avoid the poor
humidity control in summer. Therefore in the winter during design cold
weather the compressor runs, with incremental auxiliary heat. Would
suggest a long run time, compressor on steady, with heat strips cycling
on and off. It could be to the point that it is so cold outside that
the compressor is off and the home could be on full electric heat even.

Under less than extreme weather the compressor will still have a long
run time.

When you want to analyze the system from a temperature and pressure
standpoint you should wait 15 minutes for the system to stabalize. Work
backwards from 15 minutes and figure out the time constant of the
system.

Consider a furnace sized on the money for the heat load. Should be
running close to steady when the overnight lows reach and even exceed
the design levels. During weather that is cold but not at the design
level, they still run long enough to hit steady state and work at their
rated efficiency for a period of time, during mild weather they may not
run long enough to hit steady state before satisfying the thermostat.

Now consider a furnace that is oversized, runs 20 minutes on the hour
under a heating design ambient. Outdoor conditions warm up to a little
above the design level and soon not even 15 minute run time. Bulk of
the winter, at say half the design temperature differential, it never
even warms up to steady state before the thermostat is satisfied.
Wastes fuel, and heat exchanger is prematurely aged. HX ages everytime
it is heated up and cooled down.


Nick

Stretch states:

... The indoor coil will take 10 to 15 minutes to reach max coldness.

Got numbers? "Max coldness" may not be important, if it dehumidfies at 50 F
but takes 10 minutes to drop from 44 to 43.8 F.

The colder the ID coil gets, the farther below dew point it will be and
the more moisture it will take out. With a less cold coil, while it will
cool the house, it will not dehumidify well.

Why not? If we reduce the airflow, the coil becomes colder. In the limit,
we dehumidify with little cooling. With lots of airflow, we cool with no
dehumidification. And let's not forget hygroscopic house furnishings.

... A properly sized unit will run longer and dehumidify better without
losing effeicieny.

Got numbers? Is this HVAC folklore, or something to do with poor controls
in commercial systems? A 40 F coil might dehumidify equally well whether
the compressor runs 10% or 50% of the time.

... Systems do not read max efficiency till they have run an hour.
Gas furnaces are the same way.

Got numbers? An hour is a long time... to go from 99% of the max efficiency
to 99.5%? :-)

If you just lower the air flow, if you go below 350 CFM per ton, your
system will loose capacity, while using about the same electricity.

Got any numbers for us unbelievers, or simply your word as a God? :-)

Nick

Abby Normal wrote:

In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Nick

wrote:
Abby Normal wrote:

In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Nick

Not following what you are saying Nick. If what rises above dewpoint?

wrote:
Abby Normal wrote:


In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Abby did say "running the fan constantly". There's a difference between
running it somewhat more than the compressor and running it 100% of the
time. So actually, I think the two of you are talking about different
things.

- Logan

Running the fan when the compressor is off is a bad idea in a humid
climate in cooling mode.

Nick mentioned running the fan steady on low speed and cycling the
compressor. Lower speed will result in more latent removal, but the
coil will warm up quick when the compressor is off either by pressures
equalizing in a fixed metering system or just from rapidly picking up
heat from the room air.

Even having the blower cycle off 60 seconds after a compressor stops to
ring the last sensible BTU out of the thermal mass of the coil is a bad
idea with respect to humidity control.


Logan Shaw wrote:
wrote:
Abby Normal wrote:


In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Abby did say "running the fan constantly". There's a difference between
running it somewhat more than the compressor and running it 100% of the
time. So actually, I think the two of you are talking about different
things.

- Logan

Well Nick never believes anything I say but maybe if some of his
cronies say the same thing he will believe them.

I went to a seminar put on by the Florida Solar Education Center, and
as a guest speaker, they brought in an aquaintence of Nick. As soon as
I heard the guy talk, I knew that he had to know Nick. I ask the guy
and sure enough they even collaborated on magazine articles. The
seminar was on PV panels, but if these guys say something concerning
humidity it surely must be the gospel as far as Nick is concerned.

Maybe check out this link,
http://www.fsec.ucf.edu/bldg/science/mold/index.htm , and look for the
heading "Practises That WIll Minimize Mold Growth" with the subheading
"Air Conditioner Operation".

Note you hear the same things from HVAC Criminals, except the criminals
go on to say that the practise of running the fan constant while the
compressor cycles on/off can even dry out the drain pan.


Logan Shaw wrote:
wrote:
Abby Normal wrote:


In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Abby did say "running the fan constantly". There's a difference between
running it somewhat more than the compressor and running it 100% of the
time. So actually, I think the two of you are talking about different
things.

- Logan

Abby Normal wrote:

In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Not following what you are saying Nick. If what rises above dewpoint?

The coil. If it's well-controlled, always between freezing and the dew point,
moisture will not re-evaporate.

Nick

my bad, it's the Florida Solar ENERGY Center

Abby Normal wrote:
Well Nick never believes anything I say but maybe if some of his
cronies say the same thing he will believe them.

I went to a seminar put on by the Florida Solar Education Center, and
as a guest speaker, they brought in an aquaintence of Nick. As soon as
I heard the guy talk, I knew that he had to know Nick. I ask the guy
and sure enough they even collaborated on magazine articles. The
seminar was on PV panels, but if these guys say something concerning
humidity it surely must be the gospel as far as Nick is concerned.

Maybe check out this link,
http://www.fsec.ucf.edu/bldg/science/mold/index.htm , and look for the
heading "Practises That WIll Minimize Mold Growth" with the subheading
"Air Conditioner Operation".

Note you hear the same things from HVAC Criminals, except the criminals
go on to say that the practise of running the fan constant while the
compressor cycles on/off can even dry out the drain pan.


Logan Shaw wrote:
wrote:
Abby Normal wrote:


In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Abby did say "running the fan constantly". There's a difference between
running it somewhat more than the compressor and running it 100% of the
time. So actually, I think the two of you are talking about different
things.

- Logan

On 19 Dec 2005 10:01:00 -0800, "Abby Normal"
wrote:

Nick mentioned running the fan steady on low speed and cycling the
compressor. Lower speed will result in more latent removal


It sure will!

Especially if the face velocity is below the carryover threshold.
It is a critical design paramater for dehumidifiers. :-)

But since you are not reheating the air with the condenser, it acts
more like an oversized system (coil) than a dehumidifier. And I doubt
if short cycling does squat for efficiency (in fact I think it hurts,
both efficiency and the compressor).


P.S.: Why is this crossposted to misc.consumers.frugal-living?
I read all three groups, but I don't understand... this is an
engineering question, or a frugality issue?

(Maybe except for the fact that it is unfrugal to waste energy and/or
thrash an HVAC system.) ;-


--
-john
wide-open at throttle dot info

~~~~~~~~
The time to repair the roof is when the sun is shining
- JFK
~~~~~~~~

wrote:
Abby Normal wrote:

In a humid environment, running the fan constantly is a bad idea. The
reason being, as soon as the compressor shuts off, the indoor coil
warms up. The mositure still on the coil will be re-evaporated...

If it rises above the dew point. Sounds like poor control.

Not following what you are saying Nick. If what rises above dewpoint?

The coil. If it's well-controlled, always between freezing and the dew point,
moisture will not re-evaporate.

Nick


Fixed metering system, in a matter of a few seconds of that compressor
shutting off that coil is going to warm up. Pressures equalize pretty
fast.

Non bleed TX system, that air will warm up the coil fairly quick.

Your window shaker runs the fan steady as it has a sensing bulb for the
thermostat. Next summer wire your window shaker to a remote thermostat
that kills controls a contactor that kills the power to the whole unit.
The fan will then cycle with the compressor. Watch RH drop compared to
letting the fan run all the time.

Go look at the link to your solar buddies in Florida

"got numbers" = "I don't understand it"

"Abby Normal" wrote in message
oups.com...
Go look at the link to your solar buddies in Florida