I've just inherited a working 8' wide spa (AKA hot tub), fiberglass body in
a foam-insulated wooden frame with an insulated lid, holding about 700
gallons. We're going to install this outside on what was a small (non-reg.)
basketball court, and put up a windbreak around it.

My county's building code requires a separate circuit to feed the 200A 240V
draw of its control panel (AKA 'pack'), dual-stage pump and electrical
heater. Installing that circuit, and the new panel it would require (as
the existing panel can't handle it) will cost $2,400, as per two estimates
from reliable electricians.

A hot tub manufacturer's website estimates it will cost $380/year
a) to run the pump on low by timer to keep it clean,
b) to run the pump on high when we're in it, and
c) to heat it to the temp most folks like.
That assumes our electrical rate is at its current 8.4 cents per KWH.

Has anyone here reworked a similar hot tub for gas heat? Or, for solar?

Natural gas and LP gas are much less expensive to heat with here (our
electric utility is owned by Enron, happy, happy, joy, joy), and if I can
replumb it to use an on-demand heater,
http://www.realgoods.com/renew/shop/...204&ts=3006973
the heater would cost less than $800 and pay for itself in five years. It
also would reduce the size of the electrical install; I wouldn't need a
separate circuit and therefore would not need a new electrical panel.

I've also seen the Real Goods solar heating system. The Real Goods rep said
his Portland customers still need some heat in the coldest month or two,
but the rest of the time, no heat is required. This $1,900 (incl. motor
freight) system is said to be user-installable:

http://www.realgoods.com/renew/shop/...204&ts=1045209

It would be nice to use the existing control system ('pack') but those can
be had for $600
http://www.spadepot.com/Merchant2/me...y _Code=Packs
and could allow us, with pump replacement, to go 110V completely:
http://www.spadepot.com/Merchant2/me...y _Code=pumps

So, your comments regarding converting this spa to solar with gas, or
gars-only, would be appreciated. Thank you kindly in advance.


--
Nobody but a fool goes into a federal counterrorism operation without duct tape - Richard Preston, THE COBRA EVENT.

Are you sure about the 200 amp load? That's a big circuit for a portable
hot tub. Usually they are either 20 amp or 50 amp depending on the heater


John Grabowski
http://www.mrelectrician.tv
..


"Please invert everything left of the @ to reply"
wrote in message ...
I've just inherited a working 8' wide spa (AKA hot tub), fiberglass body
in
a foam-insulated wooden frame with an insulated lid, holding about 700
gallons. We're going to install this outside on what was a small
(non-reg.)
basketball court, and put up a windbreak around it.

My county's building code requires a separate circuit to feed the 200A
240V
draw of its control panel (AKA 'pack'), dual-stage pump and electrical
heater. Installing that circuit, and the new panel it would require (as
the existing panel can't handle it) will cost $2,400, as per two estimates
from reliable electricians.

A hot tub manufacturer's website estimates it will cost $380/year
a) to run the pump on low by timer to keep it clean,
b) to run the pump on high when we're in it, and
c) to heat it to the temp most folks like.
That assumes our electrical rate is at its current 8.4 cents per KWH.

Has anyone here reworked a similar hot tub for gas heat? Or, for solar?

Natural gas and LP gas are much less expensive to heat with here (our
electric utility is owned by Enron, happy, happy, joy, joy), and if I can
replumb it to use an on-demand heater,
http://www.realgoods.com/renew/shop/...204&ts=3006973
the heater would cost less than $800 and pay for itself in five years. It
also would reduce the size of the electrical install; I wouldn't need a
separate circuit and therefore would not need a new electrical panel.

I've also seen the Real Goods solar heating system. The Real Goods rep
said
his Portland customers still need some heat in the coldest month or two,
but the rest of the time, no heat is required. This $1,900 (incl. motor
freight) system is said to be user-installable:

http://www.realgoods.com/renew/shop/...204&ts=1045209

It would be nice to use the existing control system ('pack') but those can
be had for $600

http://www.spadepot.com/Merchant2/me...y _Code=Packs
and could allow us, with pump replacement, to go 110V completely:

http://www.spadepot.com/Merchant2/me...y _Code=pumps

So, your comments regarding converting this spa to solar with gas, or
gars-only, would be appreciated. Thank you kindly in advance.


--
Nobody but a fool goes into a federal counterrorism operation without duct
tape - Richard Preston, THE COBRA EVENT.

Sorry: 40A load, not 200A. Corrected version follows, and thank you, John
G., for spotting my egregious error.

On Mon, 18 Oct 2004 01:00:25 GMT, "John Grabowski"
wrote:
Are you sure about the 200 amp load? That's a big circuit for a portable
hot tub. Usually they are either 20 amp or 50 amp depending on the heater
John Grabowski
http://www.mrelectrician.tv


"Please invert everything left of the @ to reply"
wrote in message ...
I've just inherited a working 8' wide spa (AKA hot tub), fiberglass body
in a 2" foam-insulated wooden frame with an insulated lid, holding about 700
gallons. We're going to install this outside on what was a small
(non-reg.) basketball court, and put up a windbreak around it.

My county's building code requires a separate circuit to feed the 40A
240V draw of its control panel (AKA 'pack'), dual-stage pump and electrical
heater. Installing that circuit, and the new panel it would require (as
the existing panel can't handle it) will cost $2,400, as per two estimates
from reliable electricians.

A hot tub manufacturer's website estimates it will cost $380/year
a) to run the pump on low by timer to keep it clean,
b) to run the pump on high when we're in it, and
c) to heat it to the temp most folks like.
That assumes our electrical rate is at its current 8.4 cents per KWH.

Has anyone here reworked a similar hot tub for gas heat? Or, for solar?

Natural gas and LP gas are much less expensive to heat with here (our
electric utility is owned by Enron, happy, happy, joy, joy), and if I can
replumb it to use an on-demand heater,
http://www.realgoods.com/renew/shop/...204&ts=3006973
the heater would cost less than $800 and pay for itself in five years. It
also would reduce the size of the electrical install; I wouldn't need a
separate circuit and therefore would not need a new electrical panel.

I've also seen the Real Goods solar heating system. The Real Goods rep
said his Portland customers still need some heat in the coldest month or two,
but the rest of the time, no heat is required. This $1,900 (incl. motor
freight) system is said to be user-installable:

http://www.realgoods.com/renew/shop/...204&ts=1045209

It would be nice to use the existing control system ('pack') but those can
be had for $600

http://www.spadepot.com/Merchant2/me...y _Code=Packs
and could allow us, with pump replacement, to go 110V completely:

http://www.spadepot.com/Merchant2/me...y _Code=pumps

So, your comments regarding converting this spa to solar with gas, or
gas-only, would be appreciated. Thank you kindly in advance.


--
Nobody but a fool goes into a federal counterrorism operation without duct
tape - Richard Preston, THE COBRA EVENT.


--
Nobody but a fool goes into a federal counterrorism operation without duct tape - Richard Preston, THE COBRA EVENT.

On Sun, 17 Oct 2004 16:14:19 -0700, "Please invert everything left of
the @ to reply" wrote:

I've just inherited a working 8' wide spa (AKA hot tub), fiberglass body in
a foam-insulated wooden frame with an insulated lid, holding about 700
gallons. We're going to install this outside on what was a small (non-reg.)
basketball court, and put up a windbreak around it.

My county's building code requires a separate circuit to feed the 200A 240V
draw of its control panel (AKA 'pack'), dual-stage pump and electrical
heater.

200A? That's a *huge* heater and pump. Normally a spa that size
might hit a 50A or 60A circuit.

Installing that circuit, and the new panel it would require (as
the existing panel can't handle it) will cost $2,400, as per two estimates
from reliable electricians.

Well, for a 200A circuit that may be about right. But even still, you
could reconfigure with a standard 50A controller, heater and pumps for
less than $500, and *maybe* another $500 to run the new circuit.

Has anyone here reworked a similar hot tub for gas heat? Or, for solar?

Gas heat's no big deal, but you still have pumps. You'd need to buy
the gas heater and controller, but they're available for retrofit anf
may even have been an option on your model.

Solar is a waste for a spa. Can't provide enough heat rise and pretty
much sucks ofr a midnight soak.

Jeff

On Sun, 17 Oct 2004 18:34:37 -0700, "Please invert everything left of
the @ to reply" wrote:

Sorry: 40A load, not 200A. Corrected version follows, and thank you, John
G., for spotting my egregious error.

Okay, 40A and you can't pull it from an existing panel? Even the
average home on a 150A main would likely have no trouble with a 40A
spa.

But if those are the figures, I'd go with gas. Actually, I'd skip the
spa and look at upgrading my electrical service anyway.

Jeff


On Mon, 18 Oct 2004 01:00:25 GMT, "John Grabowski"
wrote:
Are you sure about the 200 amp load? That's a big circuit for a portable
hot tub. Usually they are either 20 amp or 50 amp depending on the heater
John Grabowski
http://www.mrelectrician.tv


"Please invert everything left of the @ to reply"
wrote in message ...
I've just inherited a working 8' wide spa (AKA hot tub), fiberglass body
in a 2" foam-insulated wooden frame with an insulated lid, holding about 700
gallons. We're going to install this outside on what was a small
(non-reg.) basketball court, and put up a windbreak around it.

My county's building code requires a separate circuit to feed the 40A
240V draw of its control panel (AKA 'pack'), dual-stage pump and electrical
heater. Installing that circuit, and the new panel it would require (as
the existing panel can't handle it) will cost $2,400, as per two estimates
from reliable electricians.

A hot tub manufacturer's website estimates it will cost $380/year
a) to run the pump on low by timer to keep it clean,
b) to run the pump on high when we're in it, and
c) to heat it to the temp most folks like.
That assumes our electrical rate is at its current 8.4 cents per KWH.

Has anyone here reworked a similar hot tub for gas heat? Or, for solar?

Natural gas and LP gas are much less expensive to heat with here (our
electric utility is owned by Enron, happy, happy, joy, joy), and if I can
replumb it to use an on-demand heater,
http://www.realgoods.com/renew/shop/...204&ts=3006973
the heater would cost less than $800 and pay for itself in five years. It
also would reduce the size of the electrical install; I wouldn't need a
separate circuit and therefore would not need a new electrical panel.

I've also seen the Real Goods solar heating system. The Real Goods rep
said his Portland customers still need some heat in the coldest month or two,
but the rest of the time, no heat is required. This $1,900 (incl. motor
freight) system is said to be user-installable:

http://www.realgoods.com/renew/shop/...204&ts=1045209

It would be nice to use the existing control system ('pack') but those can
be had for $600

http://www.spadepot.com/Merchant2/me...y _Code=Packs
and could allow us, with pump replacement, to go 110V completely:

http://www.spadepot.com/Merchant2/me...y _Code=pumps

So, your comments regarding converting this spa to solar with gas, or
gas-only, would be appreciated. Thank you kindly in advance.


--
Nobody but a fool goes into a federal counterrorism operation without duct
tape - Richard Preston, THE COBRA EVENT.

"Chet Hayes" wrote in message
om...
wrote in message
...
Jeff Cochran wrote:

Solar is a waste for a spa. Can't provide enough heat rise...

Evacuated tubes work well, even in cloudy climates.

and pretty much sucks ofr a midnight soak.

A spa can't store much heat, if 104 F is too cool and 106 is too warm for
people. Better to have a separate, well-insulated higher temp (170 F)
heat
store and meter it in as needed.

Drew Gillett and I have a solar water heater article in the Nov/Dec issue
of Solar Today, available soon at Borders bookstores...

Nick


I think you'll find from a practical standpoint, it's not worth
converting it to solar or gas. If it were practical, these would be
offered as options on these types of spas and they aren't. And with
solar, where you wouldn't pay for any fuel, you still will need some
other additional heat source to get it to 105, particularly during
winter. Regardless, you have to get an electric line out to it to run
the pump, blower, etc., so you still have a lot of the cost of the
electric work, even if you could avoid 240V.

One question on the $380 est for energy usage. Is that with the spa
constantly at 100+? Most spas can be programmed to come up to temp
during the times/days you will be likely to use it. Or, even without
that, you can just raise it an hour or two before you want to use it
and keep it at a lower temp, like 80 to save energy. That's what I
do, as I only use mine a couple times a week.

I keep my spa at 99 or 100. I can't imagine 105, and think that might even
be dangerous. I have a 220v. spa, and it raises the temp of water 5 degrees
F per hour. From 80 to 100 would take four hours of having the 220 on. I
believe it is less to just set it at 99, and the spa kicks on and off to use
less power. Anyway, that's the way I do it. Might not be the most
efficient, but it works for me. It is always ready to go jump into. Now
that the cooler weather is here, today is a draining day and refilling day.

I have considered a wood fired copper coil system for a mountain cabin, but
it would take a bit of preparation and maintenence. Not really worth it
unless you are living there long enough to justify it. Might work for a
home spa, but it would just get pricey and complicated IMHO. I'll stick
with the old reliable 220v system, thank you.

Steve

I have considered a wood fired copper coil system for a mountain cabin,

I tried it. 50' of 3/4 copper coiled in the top of a 55 gallon drum. I tried
wood and coal. It works but it isn't as hot as one would think and controlling
temp is hard once you get it hot.

"Greg" wrote in message
...
I have considered a wood fired copper coil system for a mountain cabin,

I tried it. 50' of 3/4 copper coiled in the top of a 55 gallon drum. I
tried
wood and coal. It works but it isn't as hot as one would think and
controlling
temp is hard once you get it hot.

I had also considered it for a Rube Goldberg type of hot water heater. A
couple of years back, I was considering a plot of land in the mountains, and
checking out systems. There is a lot available in 12v. lighting, propane
refrigeration, 12v. water pumping systems, etc. But HOT water was something
of a bear in large quantities.

So, I got a 38' motorhome instead.

STeve

I tried it. 50' of 3/4 copper coiled in the top of a 55 gallon drum. I
tried
wood and coal

I had also considered it for a Rube Goldberg type of hot water heater.

This thing would boil 30-40 gallons of water pretty quick, certainly fast
enough to supply normal hot water needs but when you have 300 gallons in an
open tub it takes a lot to make a difference.
If you put the tamk above the heater you would not even need a pump. It would
thermal siphon up there. Make damn sure you have a pop off valve so it doesn''t
blow up on you.

Don't get me wrong. Solar heat can be a cost effective and workable
solution for the right climate and the right application. But doing
this to save the few hundred dollars a year it costs to heat a home
spa is not one of them.


See me in the spring. I am fix'n to try it. My real objective is pool heating
but I am going to dump the hot water in the spa and then the pool.
(from glazed collectors)
My results are not going to transfer well if you are in Frostbite Falls Minn
tho. I am in south Florida.
This is really more of an experiment than a plan. I know I can buy myself about
10 degrees in the pool, I am just going to see what the spa does. If the solar
doesn't work I do have 11kw of heat.

BTW if gas is cheap where you are it is a good option. My 11kw (a lot more than
most spas) is only about 37,000 btu. A decent gas heater is well over
100,000btu.

"Please invert everything left of the @ to reply" wrote in message . ..
I've just inherited a working 8' wide spa (AKA hot tub), fiberglass body in
a foam-insulated wooden frame with an insulated lid, holding about 700
gallons. We're going to install this outside on what was a small (non-reg.)
basketball court, and put up a windbreak around it.

My county's building code requires a separate circuit to feed the 200A 240V
draw of its control panel (AKA 'pack'), dual-stage pump and electrical
heater. Installing that circuit, and the new panel it would require (as
the existing panel can't handle it) will cost $2,400, as per two estimates
from reliable electricians.

A hot tub manufacturer's website estimates it will cost $380/year
a) to run the pump on low by timer to keep it clean,
b) to run the pump on high when we're in it, and
c) to heat it to the temp most folks like.
That assumes our electrical rate is at its current 8.4 cents per KWH.

Has anyone here reworked a similar hot tub for gas heat? Or, for solar?

Natural gas and LP gas are much less expensive to heat with here (our
electric utility is owned by Enron, happy, happy, joy, joy), and if I can
replumb it to use an on-demand heater,
http://www.realgoods.com/renew/shop/...204&ts=3006973
the heater would cost less than $800 and pay for itself in five years. It
also would reduce the size of the electrical install; I wouldn't need a
separate circuit and therefore would not need a new electrical panel.

I've also seen the Real Goods solar heating system. The Real Goods rep said
his Portland customers still need some heat in the coldest month or two,
but the rest of the time, no heat is required. This $1,900 (incl. motor
freight) system is said to be user-installable:

http://www.realgoods.com/renew/shop/...204&ts=1045209

It would be nice to use the existing control system ('pack') but those can
be had for $600
http://www.spadepot.com/Merchant2/me...y _Code=Packs
and could allow us, with pump replacement, to go 110V completely:
http://www.spadepot.com/Merchant2/me...y _Code=pumps

So, your comments regarding converting this spa to solar with gas, or
gars-only, would be appreciated. Thank you kindly in advance.

I converted a 1986 Sundance fiberglass spa by making a woodstove heat
the water and use thermosyphon effect to circulate the water. No jets,
no electric, but I go away during the winter, so it doesn't get used
when there would be freezing temp(I drain it). It has a good
cover(really important) and heats up fairly quickly when needed with
about 1 1/2 cubic feet of pinewood. If I didn't have a wood supply, or
wanted to use it in cold times, I would bring in the 220 volts of
electricity, get the BEST cover for that model, and enjoy! Stretched
out over say 4 years your investment would cost you about the
equivelent of one seat at the movies a week, and I have never relaxed
that much at a movie!

I used to make the newbies bring me a case of beer and firewood for
using the tub, until I had so much of both that I couldn't park in my
garage, now I just let them make a donation if they want, might help
you defray your start-up costs if you did something similiar. Never
had a complaint about nudity, either, all my neighbors love to soak in
my backyard.

positively yours,

Pam

(Greg) wrote in message ...
Don't get me wrong. Solar heat can be a cost effective and workable
solution for the right climate and the right application. But doing
this to save the few hundred dollars a year it costs to heat a home
spa is not one of them.


See me in the spring. I am fix'n to try it. My real objective is pool heating
but I am going to dump the hot water in the spa and then the pool.
(from glazed collectors)
My results are not going to transfer well if you are in Frostbite Falls Minn
tho. I am in south Florida.
This is really more of an experiment than a plan. I know I can buy myself about
10 degrees in the pool, I am just going to see what the spa does. If the solar
doesn't work I do have 11kw of heat.

BTW if gas is cheap where you are it is a good option. My 11kw (a lot more than
most spas) is only about 37,000 btu. A decent gas heater is well over
100,000btu.


What you're doing in south FL sounds reasonable for many reasons:

Your spa is part of a pool, so the solar heat installation is saving
not just the spa energy cost, but the pool heating costs, which are
much larger than the heating costs of a typical stand alone home spa.

The climate is ideal

You have backup heat available

You're approaching it as an experiment, not a recommendation for
someone seeking to avoid the cost of a 240V line for a stand alone
spa.


I would also agree that gas is a good heat source for an inground
spa/pool combo like you have. However the OP has a typical small
stand alone spa. I've never seen one of these offer gas as an
alternative heat source. The gas heaters are all seperate high
capacity units, for applications like yours. I think gas is just not
practical for these types of spas due to issues like, could you fit
one inside the spa, where would the exhaust gas go, having to run gas
lines, etc. The cost savings are just not worth it, for the amount of
energy used, which is why manufacturers don't offer them. And trying
to backfit one into an existing spa with an electric heater is a lot
more cost and trouble than it's worth.

The cost savings are just not worth it, for the amount of
energy used, which is why manufacturers don't offer them

Most manufactures use a generic "skid pack" that they don't make. It is just a
quick way to get the product to market and avoid U/L listing issues.
The main downside of using gas for a spa heater is the initial cost. Once it is
installed the people I know who have it, love it. You can bring up a cold spa
to 102 in 20 minutes or so. The cost savings comes on 3 levels. You use less
chemicals in a cold spa, you don't have to pay to heat it when you aren't using
it and gas is usually cheaper than electricity.
You will have to rationalize that against a heater that may cost 3-4x what an
electric one costs but if he needs a $1000 service upgrade to hook up electric
that cost may be a wash.

Sorry Don,

I must be totally daft - what are you talking about?

All I said is that Nick's argument that temperatures in the low 60's with
high humidity would feel cold is right. Any psychometrics table supports
this.

As for what you're saying below - of course humidity is tightly controlled
in many environments! I must have missed the threads where he's arguing
that it isn't. Can you point to some specifics? I searched already but
only found the raging debates with Turtle regarding the comfort levels at
various RH's.

What am I missing here?

On Wed, 20 Oct 2004 02:41:24 -0500, Don Ocean
wrote:
Sorry...But your wrong.. Humidity is very tightly controlled for certain
equipment..Computers...Missile silos etc.. Space capsules are extremmely
contolled for Astronaut comfort and health. A real heat load takes that
into consideration. The transfer of the environment is enhance by just
the right amount of humidity. Instead of making an easy $100.. I will
merely refer you to MIT Physics department, NASA, And CERN. Nick truly
believes that humidity is witchcraft and thinks about that a lot while
cleaning the latrines at that law college. I recommend true Physics
research and ignore Nicks over the top Bull. Mother Earth magazine
had a much better concept of the inhome pyschrometrics bakc in the
1960's then Nick can even dream of. The old "Whole Earth Catalog"
had some very affordable hardware that would do the job quite well.
Researcxh that.. Some of those companies are still in business and
possibly that catalog has been updated to 2004.. I have another name
also..But that catalog is under tons of stuff in my office. One day
I will clean it out and find it or a fire will take it.. I am praying
for Fire..

Its been quite a while back... I advised someone to add a
humidifier to their home to keep the furniture from drying out
and for health concerns.. Also I mentioned that a bit can be saved on
heating costs with proper humidification. Due to the fact a few points
lower on the thermostat will feel that same as a dry house with a higher
setting. Nick denied that. And I told the fool to screw himself. He
Likes to flaunt his education to our lesser educated people and to
pooh pooh their experience knowledge. I have a degree myself..But I do
respect experience greatly. I spent some time in research in
environmental systems.. I KNOW the high cost and complexity of active
systems. And the maintenance problems with inactive systems.. Even
Eros had one fancy field of solar panels and heat storage system..The
cost of maintenance and labor got too high.. They are now back on high
efficiency standard systems. But back to Nick...Every couple of Months
he picks a stupid debate over systems that some of these lads have
worked on for years. According to Nick a full pyschrometric profile and
and a Heat load are not up to his standards of no Humidity! I understand
he runs around his own home in heavy cloths all winter long.

Astro wrote:

Sorry Don,

I must be totally daft - what are you talking about?

All I said is that Nick's argument that temperatures in the low 60's
with high humidity would feel cold is right. Any psychometrics table
supports this.

As for what you're saying below - of course humidity is tightly
controlled in many environments! I must have missed the threads where
he's arguing that it isn't. Can you point to some specifics? I searched
already but only found the raging debates with Turtle regarding the
comfort levels at various RH's.

What am I missing here?

On Wed, 20 Oct 2004 02:41:24 -0500, Don Ocean

wrote:

Sorry...But your wrong.. Humidity is very tightly controlled for
certain equipment..Computers...Missile silos etc.. Space capsules are
extremmely contolled for Astronaut comfort and health. A real heat
load takes that
into consideration. The transfer of the environment is enhance by
just the right amount of humidity. Instead of making an easy $100.. I
will merely refer you to MIT Physics department, NASA, And CERN. Nick
truly
believes that humidity is witchcraft and thinks about that a lot while
cleaning the latrines at that law college. I recommend true Physics
research and ignore Nicks over the top Bull. Mother Earth magazine
had a much better concept of the inhome pyschrometrics bakc in the
1960's then Nick can even dream of. The old "Whole Earth Catalog"
had some very affordable hardware that would do the job quite well.
Researcxh that.. Some of those companies are still in business and
possibly that catalog has been updated to 2004.. I have another name
also..But that catalog is under tons of stuff in my office. One day
I will clean it out and find it or a fire will take it.. I am praying
for Fire..

okee-dokee. Thanks for the background.
It's good to know more about the players and history in these discussions
as I get more involved in the field.

Cheers.


On Fri, 22 Oct 2004 07:23:21 -0500, Don Ocean wrote:

Its been quite a while back... I advised someone to add a
humidifier to their home to keep the furniture from drying out
and for health concerns.. Also I mentioned that a bit can be saved on
heating costs with proper humidification. Due to the fact a few points
lower on the thermostat will feel that same as a dry house with a higher
setting. Nick denied that. And I told the fool to screw himself. He
Likes to flaunt his education to our lesser educated people and to
pooh pooh their experience knowledge. I have a degree myself..But I do
respect experience greatly. I spent some time in research in
environmental systems.. I KNOW the high cost and complexity of active
systems. And the maintenance problems with inactive systems.. Even
Eros had one fancy field of solar panels and heat storage system..The
cost of maintenance and labor got too high.. They are now back on high
efficiency standard systems. But back to Nick...Every couple of Months
he picks a stupid debate over systems that some of these lads have
worked on for years. According to Nick a full pyschrometric profile and
and a Heat load are not up to his standards of no Humidity! I understand
he runs around his own home in heavy cloths all winter long.

Don Ocean wrote:

...I mentioned that a bit can be saved on heating costs with proper
humidification.

I denied that. Humidification raises fuel bills, even with a lower
thermostat setting, unless you live in an extremely airtight house.

Nick

HVAC criminal Don Ocean wrote:

...a bit can be saved on heating costs with proper humidification.

ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be equally
comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very tight, with 0.5
air changes per hour, would "proper" humidification to 50% save energy?

G = 48'x48'/R20 + 48x4x8/R20 = 192 Btu/h-F, so dropping the room temp
from 69.4 to 68 F saves 1.4x192 = 269 Btu/h. At 69.4 F and 20% RH, Pd
= 0.2e^(17.863-9621/(460+69.4)) = 0.1466, approximately, with wd
= 0.62198/(29.921/0.1466-1) = 0.003063. Air at 68 F and 50% RH has wh
= 0.007347. With 0.5x48x48x8/60 = 154 cfm of air leakage, humidifying
from wd to wh requires evaporating 154x60x0.075(wh-wd) = 2.96 pounds of
water per hour, which requires about 1000x2.96 = 2960 Btu/h of energy,
so the net "savings" is 2960-269 = -2691 Btu/h, or minus 64.6K Btu/day,
costing about $1/day more with oil heat or $2 per day with electric heat.

I've done these calcs several times now. HVAC people tend to forget that
evaporating water takes heat energy, even if a humidifier belt uses little
energy by itself, and that heat energy has to come from somewhere. And we
often get into discussions about health and furniture, vs energy and forget
that caulking a house (vs humidification) can raise the indoor RH while
SAVING on fuel bills.

Nick

wrote:

HVAC criminal Don Ocean wrote:


...a bit can be saved on heating costs with proper humidification.


ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be equally
comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very tight, with 0.5
air changes per hour, would "proper" humidification to 50% save energy?
But, too dry of indoor air causes all types of health problems such as
mucosal membrane irritation, nose bleeds, increased viral infections,
and more. Further, improper indoor humidification dries out wood
furniture and the house itself causing wall cracks and worse. So there
has to be a proper balance of humidity.
--
Think beyond your assumptions.

Serendipity wrote:

HVAC criminal Don Ocean wrote:

...a bit can be saved on heating costs with proper humidification.

ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be equally
comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very tight, with 0.5
air changes per hour, would "proper" humidification to 50% save energy?
But, too dry of indoor air causes all types of health problems such as
mucosal membrane irritation, nose bleeds, increased viral infections,
and more. Further, improper indoor humidification dries out wood
furniture and the house itself causing wall cracks and worse. So there
has to be a proper balance of humidity.

And we often get into discussions about health and furniture, vs energy,
and forget that caulking a house (vs humidification) can raise the indoor
RH while SAVING on fuel bills.

Nick

On Sun, 24 Oct 2004 09:36:06 -0400, Serendipity
wrote:

wrote:

HVAC criminal Don Ocean wrote:


...a bit can be saved on heating costs with proper humidification.


ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be equally
comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very tight, with 0.5
air changes per hour, would "proper" humidification to 50% save energy?
But, too dry of indoor air causes all types of health problems such as
mucosal membrane irritation, nose bleeds, increased viral infections,
and more. Further, improper indoor humidification dries out wood
furniture and the house itself causing wall cracks and worse. So there
has to be a proper balance of humidity.

Humidifier ........ or a pot of water on the wood stove!

Your assumptions are wrong.

They used to think that the earth was flat, too.


wrote in message
...
HVAC criminal Don Ocean wrote:

...a bit can be saved on heating costs with proper humidification.

ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be
equally
comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very tight, with
0.5
air changes per hour, would "proper" humidification to 50% save energy?

G = 48'x48'/R20 + 48x4x8/R20 = 192 Btu/h-F, so dropping the room temp
from 69.4 to 68 F saves 1.4x192 = 269 Btu/h. At 69.4 F and 20% RH, Pd
= 0.2e^(17.863-9621/(460+69.4)) = 0.1466, approximately, with wd
= 0.62198/(29.921/0.1466-1) = 0.003063. Air at 68 F and 50% RH has wh
= 0.007347. With 0.5x48x48x8/60 = 154 cfm of air leakage, humidifying
from wd to wh requires evaporating 154x60x0.075(wh-wd) = 2.96 pounds of
water per hour, which requires about 1000x2.96 = 2960 Btu/h of energy,
so the net "savings" is 2960-269 = -2691 Btu/h, or minus 64.6K Btu/day,
costing about $1/day more with oil heat or $2 per day with electric heat.

I've done these calcs several times now. HVAC people tend to forget that
evaporating water takes heat energy, even if a humidifier belt uses little
energy by itself, and that heat energy has to come from somewhere. And we
often get into discussions about health and furniture, vs energy and
forget
that caulking a house (vs humidification) can raise the indoor RH while
SAVING on fuel bills.

Nick

Oscar_Lives wrote:

Your assumptions are wrong.

Pray do explain further.

HVAC criminal Don Ocean wrote:

...a bit can be saved on heating costs with proper humidification.

ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be
equally comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very
tight, with 0.5 air changes per hour, would "proper" humidification
to 50% save energy?

G = 48'x48'/R20 + 48x4x8/R20 = 192 Btu/h-F, so dropping the room temp
from 69.4 to 68 F saves 1.4x192 = 269 Btu/h. At 69.4 F and 20% RH, Pd
= 0.2e^(17.863-9621/(460+69.4)) = 0.1466, approximately, with wd
= 0.62198/(29.921/0.1466-1) = 0.003063. Air at 68 F and 50% RH has wh
= 0.007347. With 0.5x48x48x8/60 = 154 cfm of air leakage, humidifying
from wd to wh requires evaporating 154x60x0.075(wh-wd) = 2.96 pounds of
water per hour, which requires about 1000x2.96 = 2960 Btu/h of energy,
so the net "savings" is 2960-269 = -2691 Btu/h, or minus 64.6K Btu/day,
costing about $1/day more with oil heat or $2 per day with electric heat.

I've done these calcs several times now. HVAC people tend to forget that
evaporating water takes heat energy, even if a humidifier belt uses little
energy by itself, and that heat energy has to come from somewhere. And we
often get into discussions about health and furniture, vs energy and
forget that caulking a house (vs humidification) can raise the indoor RH
while SAVING on fuel bills.

Nick

Oscar_Lives wrote:

Your assumptions are wrong.

They used to think that the earth was flat, too.

Please don't diss Nick... He thought up his Moronic
premise while cleaning the latrines at that law college(Villanova).
And Nick hasn't told the Newbies that he spends the whole winter
wearing an army blanket over his clothes in that cabin. Nick claims
to be an Engineer..But I have yet to find one Society that he belongs
to.. And he is not a registered Engineer in Pennslavania! Which actually
makes it illegal for him to consult on matters that pertain to Human
habitation! And He calls us Criminals!!! 68ºF at 42% humidity at 2240 ft
has proven to be quite comfortable for our aging citizens.. At dryer
humidity these same folks liked 74ºF to 76ºF. Now in Climates that
require a -10ºF Heatload factor..that is quite a savings..In spite of
the very small amount of energy required to produce the needed humidity.
Now with older folks in the Home and possibly small children the savings
become astronomical when looking at the health factors. And I Guess that
is why Nick spends so much time each winter..Feeling like ****! Ask him
about his annaul illnesses! I also am a believer in HEPA filters and
mold-lites where the need occurs. I recommend questions that concern
heating and cooling along with health and money savings be directed
to the Physics Depts of your State colleges.. I personally prefer MIT,
USC.. And the Small Agricultural college in Ames Iowa. They are all
geared to the heating and cooling of the future. We do have an up
and coming program at the South Dakota School of Mines.. And it is just
a bit better then the one at the University of Minnesota. Though that U
is NO slouch. Surprisingly the California colleges have really poured
some money into research. There are some full Paper Mauche houses in the
Mohave desert that have been there since the 1960's. PolyTech and
Caltech have some really top people in their research dept. Stanford
has a top Physic dept.. Ummm.. I think they still have a woman heading
the Physics Dept over at Columbia..She used to post here but got tired
of know-it-all assholes like Nick. I did stop to see her a few years
back..But she was out and time was short. , As for the world being
flat.. Thats Nicks head...From banging it against the woodburner trying
to get warm..while it was rationed to burning 3 toothpicks. ;-p

Oscar_Lives wrote:
Your assumptions are wrong.

They used to think that the earth was flat, too.

When did HVAC people used to think that the earth was flat? That's just
another one of those lies you were taught in grammar school.


wrote in message
...
HVAC criminal Don Ocean wrote:

...a bit can be saved on heating costs with proper humidification.

ASHRAE 55 says a 48x48x8' house with R20 walls and ceiling would be
equally
comfy at 69.4 F and 20% RH or 68 F and 50% RH. If it's very tight,
with
0.5
air changes per hour, would "proper" humidification to 50% save
energy?

G = 48'x48'/R20 + 48x4x8/R20 = 192 Btu/h-F, so dropping the room temp
from 69.4 to 68 F saves 1.4x192 = 269 Btu/h. At 69.4 F and 20% RH, Pd
= 0.2e^(17.863-9621/(460+69.4)) = 0.1466, approximately, with wd
= 0.62198/(29.921/0.1466-1) = 0.003063. Air at 68 F and 50% RH has wh
= 0.007347. With 0.5x48x48x8/60 = 154 cfm of air leakage, humidifying
from wd to wh requires evaporating 154x60x0.075(wh-wd) = 2.96 pounds
of water per hour, which requires about 1000x2.96 = 2960 Btu/h of
energy,
so the net "savings" is 2960-269 = -2691 Btu/h, or minus 64.6K
Btu/day, costing about $1/day more with oil heat or $2 per day with
electric heat.

I've done these calcs several times now. HVAC people tend to forget
that evaporating water takes heat energy, even if a humidifier belt
uses little energy by itself, and that heat energy has to come from
somewhere. And we often get into discussions about health and
furniture, vs energy and forget
that caulking a house (vs humidification) can raise the indoor RH
while SAVING on fuel bills.

Nick

wrote in message ...

... HVAC people tend to forget that
evaporating water takes heat energy, ...


Please.

On 24 Oct 2004 20:36:30 -0700, (Beloved
Leader) wrote:

wrote in message ...

... HVAC people tend to forget that
evaporating water takes heat energy, ...


Please.


It's a gas, man.



Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

Don Ocean wrote:

...68ºF at 42% humidity at 2240 ft has proven to be quite comfortable
for our aging citizens.. At dryer humidity these same folks liked 74ºF
to 76ºF. Now in Climates that require a -10ºF Heatload factor..that
is quite a savings..In spite of the very small amount of energy required
to produce the needed humidity.

On my planet, it takes about 1000 Btu to evaporate a pound of water.

At -10 F, wo = 0.0004608 max. At 68 F and 42% RH, wi = 0.006198. Raising
154 cfm of outdoor air to 42% RH for the previous 2304x8 ft^3 house with
0.5 ACH and 192 Btu/h-F requires evaporating 60x154x.075(wi-wo) = 3.976
pounds of water per hour, which requires about 3976 Btu/h of heat.

The ASHRAE 55 standard says people are equally comfy at 68.0 and 42% RH
and 69.7 F and 10% RH. Turning the thermostat up from 68 to 69.7 would
only add (69.7-68)192 = 326 Btu/h to the fuel bill.

Then again, you might make 42% indoor air by caulking until 60C0.075(wi-wo)
= 2x8.33/24h, ie C = 27 cfm, saving 3282 Btu/h in humidification energy plus
about (154-27)(68-(-10)) = 9906 Btu/h in heating energy, for a net savings of
13.2K Btu/h or 316.5K Btu ($5 in oil or $9 in electricity) on a -10 F day.

Nick

wrote in message ...
Don Ocean wrote:

...68ºF at 42% humidity at 2240 ft has proven to be quite comfortable
for our aging citizens.. At dryer humidity these same folks liked 74ºF
to 76ºF. Now in Climates that require a -10ºF Heatload factor..that
is quite a savings..In spite of the very small amount of energy required
to produce the needed humidity.

On my planet, it takes about 1000 Btu to evaporate a pound of water.

At -10 F, wo = 0.0004608 max. At 68 F and 42% RH, wi = 0.006198. Raising
154 cfm of outdoor air to 42% RH for the previous 2304x8 ft^3 house with
0.5 ACH and 192 Btu/h-F requires evaporating 60x154x.075(wi-wo) = 3.976
pounds of water per hour, which requires about 3976 Btu/h of heat.

The ASHRAE 55 standard says people are equally comfy at 68.0 and 42% RH
and 69.7 F and 10% RH. Turning the thermostat up from 68 to 69.7 would
only add (69.7-68)192 = 326 Btu/h to the fuel bill.

No quarrel with the rest of your analysis, but if ASHRAE 55 says that,
then it is horses**t. Hardly anybody is comfortable at 10% RH under
any conditions, and prolonged exposure to humidity that low,
especially in the absence of adequate air exchange (as can be created
by overzealous attention to insulation), is well known to encourage
upper respiratory infections.

--
Chris Green

Then again, you might make 42% indoor air by caulking until 60C0.075(wi-wo)
= 2x8.33/24h, ie C = 27 cfm, saving 3282 Btu/h in humidification energy plus
about (154-27)(68-(-10)) = 9906 Btu/h in heating energy, for a net savings of
13.2K Btu/h or 316.5K Btu ($5 in oil or $9 in electricity) on a -10 F day.

Nick

Christopher Green wrote:

The ASHRAE 55 standard says people are equally comfy at 68.0 and 42% RH
and 69.7 F and 10% RH...

No quarrel with the rest of your analysis, but if ASHRAE 55 says that,
then it is horses**t. Hardly anybody is comfortable at 10% RH...

....21,000 people say you are wrong. Then again, you can caulk.

Nick

Christopher Green wrote in message
om...
wrote
Don Ocean wrote:

...68ºF at 42% humidity at 2240 ft has proven to be quite comfortable
for our aging citizens.. At dryer humidity these same folks liked 74ºF
to 76ºF. Now in Climates that require a -10ºF Heatload factor..that
is quite a savings..In spite of the very small amount of energy required
to produce the needed humidity.

On my planet, it takes about 1000 Btu to evaporate a pound of water.

At -10 F, wo = 0.0004608 max. At 68 F and 42% RH, wi = 0.006198. Raising
154 cfm of outdoor air to 42% RH for the previous 2304x8 ft^3 house with
0.5 ACH and 192 Btu/h-F requires evaporating 60x154x.075(wi-wo) = 3.976
pounds of water per hour, which requires about 3976 Btu/h of heat.

The ASHRAE 55 standard says people are equally comfy at 68.0
and 42% RH and 69.7 F and 10% RH. Turning the thermostat up
from 68 to 69.7 would only add (69.7-68)192 = 326 Btu/h to the fuel bill.

No quarrel with the rest of your analysis, but if ASHRAE 55
says that, then it is horses**t. Hardly anybody is comfortable
at 10% RH under any conditions,

Oh bull****. I am most days in summer.

and prolonged exposure to humidity that low, especially
in the absence of adequate air exchange (as can be
created by overzealous attention to insulation), is well
known to encourage upper respiratory infections.

How odd that I havent had one in decades now.

You are missing a large heat loss factor.

Comfort is due largely to the body's ability to sense the rate of heat
transfer.

You have not stated your assumptions but it is apparent you think most
heat transfer from the body is due to convection, to the ambient air.
That would make air temperature and humidity the important factors.

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls. Since radiative
heat transfer depends on the fourth power temperature delta, cold
walls can make you feel cold even when the air is warm and humid.

TimR wrote:

You have not stated your assumptions but it is apparent you think most
heat transfer from the body is due to convection, to the ambient air.

Sometimes.

That would make air temperature and humidity the important factors.

Among others. I've been using the ASHRAE 55-2004 comfort model's
BASIC program with equal air and radiant temps (TA=TR below.)

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls.

You might enjoy exploring that factor, using actual numbers.

ASHRAE-standard 55-2004 ("Thermal environmental conditions for human
occupancy") defines two "comfort zones," winter (with a clo = 1 clothing
thermal resistance) and summer (clo = 0.5.) Its BASIC program estimates
the Predicted Mean Vote (PMV: +3 hot, +2 warm, +1 slightly warm, 0 neutral,
-1 slightly cool, -2 cool, and -3 cold) and the Predicted Percentage
Dissatisfied (PPD) based on clothing, activity, metabolic rate, external
work, air temp, mean radiant temp, air velocity, and RH...

50 CLO = 1'clothing insulation (clo)
60 MET=1.1'metabolic rate (met)
70 WME=0'external work (met)
80 TA=19.6'air temp (C)
90 TR=19.6'mean radiant temp (C)
100 VEL=.1'air velocity (m/s)
120 RH=86'relative humidity (%) make one of RH or PA non-zero...
130 PA=0'water vapor pressure
140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa
150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa
160 ICL=.155*CLO'clothing resistance (m^2K/W)
170 M=MET*58.15'metabolic rate (W/m^2)
180 W=WME*58.15'external work in (W/m^2)
190 MW=M-W'internal heat production
200 IF ICL.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor
210 HCF=12.1*SQR(VEL)'forced convection conductance
220 TAA=TA+273'air temp (K)
230 TRA=TR+273'mean radiant temp (K)
250 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp
260 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermed iate values
300 P5=308.7-.028*MW+P2*(TRA/100)^4
310 XN=TCLA/100
320 XF=XN
330 N=0'number of iterations
340 EPS=.00015'stop iteration when met
350 XF=(XF+XN)/2'natural convection conductance
360 HCN=2.38*ABS(100*XF-TAA)^.25
370 IF HCFHCN THEN HC=HCF ELSE HC=HCN
380 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
390 N=N+1
400 IF N150 GOTO 550
410 IF ABS(XN-XF)EPS GOTO 350
420 TCL=100*XN-273'clothing surface temp (C)
440 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin
450 IF MW58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating
460 HL3=.000017*M*(5867-PA)'latent respiration heat loss
470 HL4=.0014*M*(34-TA)'dry respiration heat loss
480 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation
490 HL6=FCL*HC*(TCL-TA)'heat loss by convection
510 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient
520 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote
530 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied
540 GOTO 580
550 PMV=99999!:PPD=100
580 PRINT TA,RH,CLO,PMV,PPD

T (C) RH clo PMV PPD

19.6 86 1 -.4778556 9.769089
23.9 66 1 .4732535 9.676994
25.7 15 1 .5239881 10.74283
21.2 20 1 -.4779105 9.770202
23.6 67 .5 -.4747404 9.706658
26.8 56 .5 .5145492 10.53611
27.9 13 .5 .5003051 10.23146
24.7 16 .5 -.4883473 9.982468

The first 4 lines are the winter comfort zone corners.
The second 4 lines are the summer comfort zone corners.

Nick

TimR wrote:

You are missing a large heat loss factor.

Comfort is due largely to the body's ability to sense the rate of heat
transfer.

You have not stated your assumptions but it is apparent you think most
heat transfer from the body is due to convection, to the ambient air.
That would make air temperature and humidity the important factors.

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls. Since radiative
heat transfer depends on the fourth power temperature delta, cold
walls can make you feel cold even when the air is warm and humid.

Well Tim lad... I live in South Dakota.. And I realize that is the
tropical Zone. But we do use forced air heat to the outside walls and
returns to the inside walls. And by your thinking Phoenix with hot
outside walls must be in a world of hurt(NOT!). Our tropical weather in
South Dakota and in our neighbors ..North Dakota Minnesota...Canada ..
usually requires 6 inches or equivalent of insulation in outside walls.
And in my Little grass shack You can't even begin to get into the attic
for the depth of insulation. Also all surfaces that have non conditioned
space on the outside..has a first class vapor barrier... outside under
the siding has a Tyvac unbroken except for windows and doors. Hot water
systems run through floors and outside walls.. And baseboards are on the
outside walls. Times have changed since the day of the localized space
heaters. Many FA furnaces keep conditioned air moving at all times..
with only a variable speed fan. So a cold outside wall is actually
cureable and even our garages have that already resolved with
insulation. I will admit our banana crop gets a bit brittle to eat in
the less then tropical season. Has something to do with those Siberian
fronts that comne to visit us from time to time.

Don Ocean wrote:

TimR wrote:

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls. Since radiative
heat transfer depends on the fourth power temperature delta, cold
walls can make you feel cold even when the air is warm and humid.

How cold? To investigate this, you might make TA = 70 F and
TR = 70-R0.66(70-30)/(R20+R0.66) = 68.7 in that BASIC program,
for an R20 wall on a 30 F day.

Well Tim lad... I live in South Dakota.. And I realize that is the
tropical Zone. But we do use forced air heat to the outside walls and
returns to the inside walls...

Then again, warm air rises. Harry Thomason used a central supply with the
heat source in the basement and a long slotted grill near the ceiling to
make a thermal chimeny and floor returns near outside walls to make good
natural airflow.

This keeps the outside walls slightly cooler. We might make up for that
by slightly raising the room temp, and end up using less energy.

Nick

TimR wrote:

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls. Since radiative
heat transfer depends on the fourth power temperature delta, cold
walls can make you feel cold even when the air is warm and humid.

How cold? To investigate this, you might make TA = 70 F and
TR = 70-R0.66(70-30)/(R20+R0.66) = 68.7 in that BASIC program,
for an R20 wall on a 30 F day.

Making 1 exterior wall of a 20x20' room 68.7 F makes the mean radiant
room temp about 69.82, which requires raising the room air temp from
70 to 70.15 F to keep the same comfort level. No big deal. Perhaps you
came up with a similar answer, or maybe you had no idea of the answer.
The latter seems more likely, given your posting.

Don Ocean wrote:

...we do use forced air heat to the outside walls and returns
to the inside walls.

That wastes energy...

...warm air rises. Harry Thomason used a central supply with the heat
source in the basement and a long slotted grill near the ceiling to
make a thermal chimney and floor returns near outside walls to make
good natural airflow.

Which can save 400 watts of blower power and significant heat energy.

Adding a 4'x8' R2 window to the exterior wall above with a supply vent
underneath which creates 4 Btu/h-F-ft^2 of moving airfilm conductance
makes the indoor window surface temp 65.77 F and the interior surface
of the exterior wall 68.94 and mean radiant room temp about 69.71, which
requires raising the room air temp to 70.24 to keep the same comfort level.

This room requires about (65.77-30)4'x8'/R2 = 572 Btu/h for the window
+ (68.94-30)128ft^2/R20 = 249 Btu/h for the wall, a total of 821 Btu/h.

This keeps the outside walls slightly cooler. We might make up for that
by slightly raising the room temp, and end up using less energy.

With a lower-velocity lower-temp return vs supply under the window and
a 1.5 Btu/h-F-ft^2 slow-moving airfilm conductance near the window, its
indoor surface becomes 60.30 F, the interior surface of the exterior
wall becomes 69.10, and the mean radiant room temp becomes about 69.52,
which requires raising the room air temp to 70.40 to keep the same comfort.

This room requires about (60.30-30)4'x8'/R2 = 485 Btu/h for the window
+ (69.10-30)128ft^2/R20 = 250 Btu/h for the wall, a total of 735 Btu/h,
about 10% less than the previous room, with a supply register under
the window. This room is equally comfortable, unless we sit close to
the unshaded window.

Nick

10 CLO = 1.2276'clothing insulation (clo)
20 MET=1.1'metabolic rate (met)
30 WME=0'external work (met)
40 TAF=70.23841'air temp (F)
50 TA=(TAF-32)/1.8'air temp (C)
60 TWALLF=30+(TAF-30)/(20+2/3)*20'inside wall temp (F)
70 GW=4'indoor window air film conductance (Btu/h-F-ft^2)
80 TWINDF=30+(TAF-30)/(2+1/GW)*2'inside window temp (F)
90 TRF=(22.6*TWINDF+67.4*TWALLF+270*TAF)/360
100 TR=(TRF-32)/1.8'mean radiant temp (C)
110 VEL=.1'air velocity
120 RH=50'relative humidity (%)
130 PA=0'water vapor pressure
140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa
150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa
160 ICL=.155*CLO'clothing resistance (m^2K/W)
170 M=MET*58.15'metabolic rate (W/m^2)
180 W=WME*58.15'external work in (W/m^2)
190 MW=M-W'internal heat production
200 IF ICL.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor
210 HCF=12.1*SQR(VEL)'forced convection conductance
220 TAA=TA+273'air temp (K)
230 TRA=TR+273'mean radiant temp (K)
240 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp
250 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermed iate values
260 P5=308.7-.028*MW+P2*(TRA/100)^4
270 XN=TCLA/100
280 XF=XN
290 N=0'number of iterations
300 EPS=.00015'stop iteration when met
310 XF=(XF+XN)/2'natural convection conductance
320 HCN=2.38*ABS(100*XF-TAA)^.25
330 IF HCFHCN THEN HC=HCF ELSE HC=HCN
340 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
350 N=N+1
360 IF N150 GOTO 490
370 IF ABS(XN-XF)EPS GOTO 310
380 TCL=100*XN-273'clothing surface temp (C)
390 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin
400 IF MW58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating
410 HL3=.000017*M*(5867-PA)'latent respiration heat loss
420 HL4=.0014*M*(34-TA)'dry respiration heat loss
430 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation
440 HL6=FCL*HC*(TCL-TA)'heat loss by convection
450 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient
460 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote
470 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied
480 GOTO 500
490 PMV=99999!:PPD=100
500 PRINT TAF,TWALLF,TWINDF,TRF,PMV

70.23841 68.9404 65.76747 69.71472 1.408771E-04

Innova AirTech Instruments has an excellent comfort web site...

http://www.impind.de.unifi.it/Impind...va/thermal.htm

wrote in message
...
TimR wrote:

You have not stated your assumptions but it is apparent you think most
heat transfer from the body is due to convection, to the ambient air.

Sometimes.

That would make air temperature and humidity the important factors.

Among others. I've been using the ASHRAE 55-2004 comfort model's
BASIC program with equal air and radiant temps (TA=TR below.)

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls.

You might enjoy exploring that factor, using actual numbers.

ASHRAE-standard 55-2004 ("Thermal environmental conditions for human
occupancy") defines two "comfort zones," winter (with a clo = 1 clothing
thermal resistance) and summer (clo = 0.5.) Its BASIC program estimates
the Predicted Mean Vote (PMV: +3 hot, +2 warm, +1 slightly warm, 0
neutral,
-1 slightly cool, -2 cool, and -3 cold) and the Predicted Percentage
Dissatisfied (PPD) based on clothing, activity, metabolic rate, external
work, air temp, mean radiant temp, air velocity, and RH...


snip the basic program

Hi Nick, but I wonder about setting the radiant temperature equal to the air
temperature. I have this running argument with the Mrs. every winter. The
thermometer in two different rooms reads the same, but the one with a large
sliding glass door (well weatherstripped and draft-free, to be sure), always
'feels' colder. I say it is because of the large radiant losses out this
window and we just need to install some heavy draperies. She's dead set
against draperies in the room from an interior decorator point of view.

If you run with TR set to a lower number then TA, surely you get a different
result. But how can one easily determine the TR when standing in the middle
of a room where three walls are conventional, interior walls near TA, but
one is a large amount of double-pane glass to a 20F exterior night??

Any thoughts???

daestrom

wrote in message
...
TimR wrote:

In cold climates in the winter, a large factor you have missed is
radiative heat transfer to the cold exterior walls. Since radiative
heat transfer depends on the fourth power temperature delta, cold
walls can make you feel cold even when the air is warm and humid.

How cold? To investigate this, you might make TA = 70 F and
TR = 70-R0.66(70-30)/(R20+R0.66) = 68.7 in that BASIC program,
for an R20 wall on a 30 F day.


But I wonder if that is always the correct method to calculate TR.
Certainly, if the exterior wall is constructed with the same surface
emissivity as the interior walls (all wallboard) it would work. But
wouldn't the affects of windows, through which there are more radiant losses
have to be handled differently?

It just 'seems' that since some IR passes *through* a double pane window,
while an ordinary wall-board wall is opaque to IR, that the two *have* to be
handled differently.

daestrom

daestrom wrote:

...how can one easily determine the TR when standing in the middle of
a room where three walls are conventional, interior walls near TA, but
one is a large amount of double-pane glass to a 20F exterior night??

The inside surface of an R2 window with an R0.66 inside airfilm might
be 20+2(70-20)/2.66 = 57.5 on a 20 F night. You can calculate Tr using
solid angles. If the room is square and 3 walls are 70 F and one is 57.5,
Tr = (270x70+90x57.5)/360 = 66.9, for an observer in the middle of the
room, ignoring the floor and ceiling.

The SBSE tool kit contains a grey golf ball for slipping over a probe
to measure the mean radiant temperature.

Nick

daestrom wrote:

wouldn't the affects of windows, through which there are more radiant losses
have to be handled differently?

IIRC, windows block IR over 3 microns, eg 10 micron 80 F IR.

Nick