Heating a pool with an air conditioner

[DerbyDad03]

Ask This Old House showed the installation of a system that captures the
heat from the AC unit to heat a swimming pool. The AC refrigerant line runs
through a coil inside a canister. The pool water runs through the canister
and the heat is extracted.

OK, that's all well and good. Efficient, free heat heat for a pool which is
shaded by trees and gets very little sun.

Let's think about this. When it's hot out, the AC is running and pool gets
heated. When it's cool out, the AC is not running, so the pool does not get
heated.

Sure, there's some advantage to heating the pool on a hot day, even into
the hot night. However, on a cool day or cool evening, when the owner would
really want the pool heated, he's right back where he was before the system
was installed. Early and late in the season, when it's not hot enough for
the AC to be running for any length of time, there is no heat available for
the pool - right at the times of the season when you would want it.

Considering that it takes a certified AC tech to capture the refrigerant,
adapt the AC piping and recharge the system, is it really worth installing
one of these systems? I don't have a pool, so I don't know how cold the
water in a shaded pool would be on a day hot enough for the AC to be
running.

After a few days of cool weather, how long would would the AC have to be
running for it to heat the pool to something that would be comfortable?
Yes, I know it depends on the size of the pool and how cool it was. The one
in the show was a decent sized in ground pool. Is it a matter of a few
hours or would it take all day or longer? I know there's a number of
variables involved...just looking for some idea.

It just seems kind of bass-akwards to only have heat available on hot days.

 

[trader4]

Ask This Old House showed the installation of a system that captures the
heat from the AC unit to heat a swimming pool. The AC refrigerant line runs
through a coil inside a canister. The pool water runs through the canister
and the heat is extracted.

OK, that's all well and good. Efficient, free heat heat for a pool which is
shaded by trees and gets very little sun.

Let's think about this. When it's hot out, the AC is running and pool gets
heated. When it's cool out, the AC is not running, so the pool does not get
heated.

Sure, there's some advantage to heating the pool on a hot day, even into
the hot night. However, on a cool day or cool evening, when the owner would
really want the pool heated, he's right back where he was before the system
was installed. Early and late in the season, when it's not hot enough for
the AC to be running for any length of time, there is no heat available for
the pool - right at the times of the season when you would want it.

Considering that it takes a certified AC tech to capture the refrigerant,
adapt the AC piping and recharge the system, is it really worth installing
one of these systems? I don't have a pool, so I don't know how cold the
water in a shaded pool would be on a day hot enough for the AC to be
running.

After a few days of cool weather, how long would would the AC have to be
running for it to heat the pool to something that would be comfortable?
Yes, I know it depends on the size of the pool and how cool it was. The one
in the show was a decent sized in ground pool. Is it a matter of a few
hours or would it take all day or longer? I know there's a number of
variables involved...just looking for some idea.

It just seems kind of bass-akwards to only have heat available on hot days.

You may not have a pool, but I say you're on the right track.
You're right, durintg the times you are most likely to want to heat
the pool, the AC will not be running much. When the AC is running a
lot, you're not likely to need it much to warm
the pool. Here in NJ the AC is running a lot in Jul and Aug,
precisely the time you typically don't need to heat the pool.

Also take a look at the BTUs of a typical pool heater.
I have one here that is gas, 400K BTUs for a 48,000 gal
pool. You can scale that for other sizes. They don't
put 400K btu heaters in for nothing. It takes a hell of
a lot of energy to heat all that water. A 4 ton AC by
comparison is only 48,000 BTUs, an order of magnitude
smaller

And also a lot of the heat from a pool is quickly lost,
so you can't keep building it up over days.
So, if you have a couple days of putting heat into it
with the AC system, then days where it doesn't heat,
in a day it will be cooled down again. That can be
slowed by using a thermal pool cover, but that is
yet another obvious pain to put up with.

So, yeah, I'd say the whole thing is dumb and
I would not spend a nickel on it.

 

[DD_BobK]

I can easily see it in addition to fire, and the air conditioner will be
more efficient when it's used. I guess fire takes over when the air is not
used,but it has to do both ways.

Greg

DD & Greg are both correct. In concept it's a good idea but whether
it really works well & pays is all about the numbers.
How much energy does the AC remove & when, seasonal & daily basis.
How much energy does the pool need & when, seasonal & daily basis.

How well these two systems "match up" will determine viability.

Even a very large AC load (5+ tons) would still be much smaller than
most pool heaters.

But, the "heat" from the AC is essentially free once the system mods
were made.
Providing a few tons (24,000 to 50,000 btu/hr) would lower your
natural gas bill.

Like, Greg, I see this AC pool heater as supplying some sort of
baseline heating with a gas fired unit also being required.

imo, the AC pool heater would lower yearly energy costs but not
eliminate the need for a conventional heater... unless the owner was
satisfied with a "greener" but lower performing pool heating system.

cheers
Bob

 

[gonjah]

Ask This Old House showed the installation of a system that captures the
heat from the AC unit to heat a swimming pool. The AC refrigerant line runs
through a coil inside a canister. The pool water runs through the canister
and the heat is extracted.

OK, that's all well and good. Efficient, free heat heat for a pool which is
shaded by trees and gets very little sun.

Let's think about this. When it's hot out, the AC is running and pool gets
heated. When it's cool out, the AC is not running, so the pool does not get
heated.

Sure, there's some advantage to heating the pool on a hot day, even into
the hot night. However, on a cool day or cool evening, when the owner would
really want the pool heated, he's right back where he was before the system
was installed. Early and late in the season, when it's not hot enough for
the AC to be running for any length of time, there is no heat available for
the pool - right at the times of the season when you would want it.

Considering that it takes a certified AC tech to capture the refrigerant,
adapt the AC piping and recharge the system, is it really worth installing
one of these systems? I don't have a pool, so I don't know how cold the
water in a shaded pool would be on a day hot enough for the AC to be
running.

After a few days of cool weather, how long would would the AC have to be
running for it to heat the pool to something that would be comfortable?
Yes, I know it depends on the size of the pool and how cool it was. The one
in the show was a decent sized in ground pool. Is it a matter of a few
hours or would it take all day or longer? I know there's a number of
variables involved...just looking for some idea.

It just seems kind of bass-akwards to only have heat available on hot days.

I can see it working but, summer before last, I was trying to cool my
pool down. Now I use "Sun Sails" and cover the majority of the pool with
shade.

Nat. gas is so cheap here it doesn't seem like the savings would cover
the cost of the conversion anytime soon.

Interesting idea though, and maybe I should be watching "TOH" more.

 

[recyclebinned]

Is the refrigerant coil made of copper?
How long will that coil last in
chlorinated or salted water?

 

[Malcom \Mal\ Reynolds]

DD & Greg are both correct. In concept it's a good idea but whether
it really works well & pays is all about the numbers.
How much energy does the AC remove & when, seasonal & daily basis.
How much energy does the pool need & when, seasonal & daily basis.

How well these two systems "match up" will determine viability.

Even a very large AC load (5+ tons) would still be much smaller than
most pool heaters.

But, the "heat" from the AC is essentially free once the system mods
were made.
Providing a few tons (24,000 to 50,000 btu/hr) would lower your
natural gas bill.

Like, Greg, I see this AC pool heater as supplying some sort of
baseline heating with a gas fired unit also being required.

imo, the AC pool heater would lower yearly energy costs but not
eliminate the need for a conventional heater... unless the owner was
satisfied with a "greener" but lower performing pool heating system.

cheers
Bob

If we're talking a heat pump here, then in the winter, the HP is going to pull
heat out of the pool which may have a very nice financial payback...it's going
to work like a geothermal pump but not as expensive. Downside is that it may
take longer to heat the thing up in the summer and will make the pool unusable
in the winter

 

[DerbyDad03]

I can see it working but, summer before last, I was trying to cool my
pool down. Now I use "Sun Sails" and cover the majority of the pool with shade.

Nat. gas is so cheap here it doesn't seem like the savings would cover
the cost of the conversion anytime soon.

Interesting idea though, and maybe I should be watching "TOH" more.

Make sure you watch ATOH or the The TOH Hour. Just watching TOH won't get
you what I saw.

 

[DerbyDad03]

Since the pool water is colder than the outdoor air, it could also lower
your electric bill for the AC.

Liquid cooled condensors have been in use for years, but usually commercial
applications.

My sense, is that there won't be enough return for the investment.

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


But, the "heat" from the AC is essentially free once the system mods
were made.
Providing a few tons (24,000 to 50,000 btu/hr) would lower your
natural gas bill.


cheers
Bob

They did indeed say the the AC unit will run more efficiently.

 

[Robert Neville]

Let's think about this. When it's hot out, the AC is running and pool gets
heated. When it's cool out, the AC is not running, so the pool does not get
heated.

It's not about heating the pool, it's about the cooling the house. Air
conditiioners are heat transfer devices. They move heat from one location to the
other. Transfering heat by means of a fan to the outdoor warm air is far less
efficient than transfering it to cooler water.

 

[DerbyDad03]

It's not about heating the pool, it's about the cooling the house. Air
conditiioners are heat transfer devices. They move heat from one location to the
other. Transfering heat by means of a fan to the outdoor warm air is far less
efficient than transfering it to cooler water.

No, it was about heating the pool. Watch the latest episode of Ask This Old
House when you get a chance. The system was installed for the sole purpose
of heating a shaded in-ground pool. It was plumbed in before the pool
filter and included a sensor that only allowed the refrigerant to flow
through the canister's coil when the pool water needed heating.

The fact that the AC would be more efficient when it was heating the pool
water is just an added bonus. If it was about cooling the house, then the
sensor would not have been installed.

The fact that

 

[harry]

Ask This Old House showed the installation of a system that captures the
heat from the AC unit to heat a swimming pool. The AC refrigerant line runs
through a coil inside a canister. The pool water runs through the canister
and the heat is extracted.

OK, that's all well and good. Efficient, free heat heat for a pool which is
shaded by trees and gets very little sun.

Let's think about this. When it's hot out, the AC is running and pool gets
heated. When it's cool out, the AC is not running, so the pool does not get
heated.

Sure, there's some advantage to heating the pool on a hot day, even into
the hot night. However, on a cool day or cool evening, when the owner would
really want the pool heated, he's right back where he was before the system
was installed. Early and late in the season, when it's not hot enough for
the AC to be running for any length of time, there is no heat available for
the pool - right at the times of the season when you would want it.

Considering that it takes a certified AC tech to capture the refrigerant,
adapt the AC piping and recharge the system, is it really worth installing
one of these systems? I don't have a pool, so I don't know how cold the
water in a shaded pool would be on a day hot enough for the AC to be
running.

After a few days of cool weather, how long would would the AC have to be
running for it to heat the pool to something that would be comfortable?
Yes, I know it depends on the size of the pool and how cool it was. The one
in the show was a decent sized in ground pool. Is it a matter of a few
hours or would it take all day or longer? I know there's a number of
variables involved...just looking for some idea.

It just seems kind of bass-akwards to only have heat available on hot days.

Well you'd only be using the pool on warm days.
So makes perfect sense.

 

[The Daring Dufas]

Is the refrigerant coil made of copper?
How long will that coil last in
chlorinated or salted water?

I won't call you names over it because most folks don't know what's in
the AC/pool heat exchangers. Here's a link for the type heat exchanger
used for pool and marine applications. ^_^

http://www.pexsupply.com/Marine-Swim-Pool-Heat-Exchangers-MPN-Series-5x12-1065000

http://tinyurl.com/a7q9zbc

TDD

 

[DerbyDad03]

I won't call you names over it because most folks don't know what's in
the AC/pool heat exchangers. Here's a link for the type heat exchanger
used for pool and marine applications. ^_^

http://www.pexsupply.com/Marine-Swim-Pool-Heat-Exchangers-MPN-Series-5x12-1065000

http://tinyurl.com/a7q9zbc

TDD

OP here...

On the show, Richard Trethewey specifically mentioned a coil and did that
circular thing with his hand around the canister. Just sayin'

 

[trader4]

It's not about heating the pool, it's about the cooling the house. Air
conditiioners are heat transfer devices. They move heat from one locationto the
other. Transfering heat by means of a fan to the outdoor warm air is far less
efficient than transfering it to cooler water.

I think those of you that think this is going to make
a substantial difference in cooling costs to the house are
barking up the wrong tree. It's true if you had the same
size condenser that you could get more cooling out of
it by using water on the condenser instead of air. But
the condenser the AC unit already has consists of a coil
and fan that are sufficient and sized so that it brings
the refrigerant temp down close to that of the outside
ambient air. It does that with an electric fan
that probably uses less energy than the pool pump
would. If you feel the pressure line where
it enters the air handler it's around room temp. A
pool in the months when you need AC is going to be
around 80F. So, you're not going to drop the
refrigerant temp any more than that by passing pool
water over it. In other words, I don't see it making
a difference.

And the suggestion to use the pool with a heat pump
to get heat in the winter is pretty much a non-starter,
IMO, too. In the climates where it would make the most
impact you have freezing temps. Pools and the existing
pool eqpt are not designed to operate in freezing conditions. I
guess you could do it in FL, but given the climate, little
need for heat, why bother? And as for heating the pool
down there, in the months when it would work, they
actually are cooling some pools because they get too
hot on their own, no?

 

[trader4]

Well you'd only be using the pool on warm days.
So makes perfect sense.- Hide quoted text -

- Show quoted text -

We can add pools to the list of subjects you obviously are
clueless about.

 

[The Daring Dufas]

OP here...

On the show, Richard Trethewey specifically mentioned a coil and did that
circular thing with his hand around the canister. Just sayin'

Was it stainless steel? A lot of guys I know will call any heat
exchanger "the coil" even though the item may be in different forms
but I did not pay close enough attention to the coil in canister bit,
my bad but I'm sure the coil in canister wasn't bare copper. The flat
plate exchangers I posted the link are not made of copper but rather
stainless steel. **I found the heat exchanger you mentioned, it's not
stainless steel, it's freaking "titanium". The video link is there too!
I always use flat plate heat exchangers in the systems I work on so I
automatically think of that type. I've never used one made of titanium
and I think it's so cool(no pun).

http://www.hotspotenergy.com/pool-heater/

TDD

 

[The Daring Dufas]

We can add pools to the list of subjects you obviously are
clueless about.

Heck, the only time I have a pool out back of my shack is when it rains.
'course we can put thick plastic in the bed of the pickup
and fill it with water. ^_^

TDD

 

[gpsman]

Let's think about this. When it's hot out, the AC is running and pool gets
heated. When it's cool out, the AC is not running, so the pool does not get
heated.

Via the AC, which is obviously woefully insufficient to heat the
standard 16x32 ±20K gallon pool.

Seems it must be a system auxiliary to a dedicated heater.

 

[trader4]

I think those of you that think this is going to make
a substantial difference in cooling costs to the house are
barking up the wrong tree.  It's true if you had the same
size condenser that you could get more cooling out of
it by using water on the condenser instead of air.  But
the condenser the AC unit already has consists of a coil
and fan that are sufficient and sized so that it brings
the refrigerant temp down close to that of the outside
ambient air.  It does that with an electric fan
that probably uses less energy than the pool pump
would.   If you feel the pressure line where
it enters the air handler it's around room temp.  A
pool in the months when you need AC is going to be
around 80F.   So, you're not going to drop the
refrigerant temp any more than that by passing pool
water over it.  In other words, I don't see it making
a difference.

After posting this, I realized there was one aspect
I overlooked. I compared the electricity to run the pool
pump with the electricity to run the pool pump. But
the electricity used by the pool pump can probably
be ignored because the pool pump typically runs 6 or
8 hours a day to filter the pool water anyway. So,
it can be filtering while doing the AC.

In which case, I can see the system saving basicly
whatever it took to run the fan motor on the AC
condenser. Which is something. But the whole thing
appears very impractical to me for a variety of reasons.
The biggest obstacle being the mismatch between the
periods when you need it most and when the AC is actually
running the most. For example, here in NJ, when the
heating is most useful is late May and June at the
beginning of the season and Sept to extend the season
for a few weeks. Those times the AC is not running
all that much.

 

[gonjah]

OP here...

On the show, Richard Trethewey specifically mentioned a coil and did that
circular thing with his hand around the canister. Just sayin'

I think this is the episode. It's the 3rd scene selection:

http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,20652494,00.html

Titanium.

FWIW: My pool heaters heat exchangers are copper.