Heating a pool with an air conditioner

[Dan Espen]

That is the essential energy difference. Now let's say
that the ambient air is 80F and the pool water is also 80F.

I've seen this stated a few times in this thread and I don't think it's
true. The pool temperature is going to be the average of daytime and
nighttime temperature plus the effect of evaporative cooling at the
water surface, plus the effect of cooling due to ground temperature.

All and all, I'd expect the pool water during the time the AC is in use
to be significantly lower than the air temperature.

Before I had my heater, with air temps in the upper 90s I'd still have
the water at 80 or so. If I remember right, 82 was an all time high.

The heating from the AC system heat exchanger isn't going to make much
of a difference for pool temperature but the AC system will cool better.

 

[trader4]

I've seen this stated a few times in this thread and I don't think it's
true. The pool temperature is going to be the average of daytime and
nighttime temperature plus the effect of evaporative cooling at the
water surface, plus the effect of cooling due to ground temperature.

All and all, I'd expect the pool water during the time the AC is in use
to be significantly lower than the air temperature.





Before I had my heater, with air temps in the upper 90s I'd still have
the water at 80 or so.  If I remember right, 82 was an all time high.

That depends on the particular climate and if the pool is
shaded or full sun. Here in NJ/NYC for example, pools that
have mostly sun are in the low 80s
without heat during July and Aug. And that is with daytime
temps in the 80s. If it's upper 90s for a couple days, pool
could be 85+ with no heater. The time folks here typically
use a pool heater, if at all, is in the beginning of the season, ie
late May, early June and again going into Sept. The
problem with that is during those periods the AC is
running the least. It's a mismatch between when it's
needed most and when the most heat is available.

I agree there are going to be some days when the pool
water temp will be below the air temp. But look at it
from this perspective. If the system works to do what
is wanted, then the pool should be 80+, no? Isn't that
a purpose of the pool heater? So, if the water is 80 - 85,
reagardless of how it gets there, I don't see that as being
a big difference versus the ambient air if you average
it out. For example, at night, the pool at times could
actually be above the ambient air temp, right?
If you;re saying, well the pool could be 75 and the
ambient air 90, sure I could see that, but that situation
has to be an exception, or else the thing isn't heating
the pool enough, right? If it's working, then you
should have 90 air, 85 water.

The heating from the AC system heat exchanger isn't going to make much
of a difference for pool temperature but the AC system will cool better.

But the main point of the whole TOH project was to
heat the pool. That was the original problem, not that
they wanted to lower the AC bill. The lowering of the
AC bill was an additional benefit.

 

[Dan Espen]

That depends on the particular climate and if the pool is
shaded or full sun. Here in NJ/NYC for example, pools that
have mostly sun are in the low 80s
without heat during July and Aug. And that is with daytime
temps in the 80s. If it's upper 90s for a couple days, pool
could be 85+ with no heater. The time folks here typically
use a pool heater, if at all, is in the beginning of the season, ie
late May, early June and again going into Sept. The
problem with that is during those periods the AC is
running the least. It's a mismatch between when it's
needed most and when the most heat is available.

I agree there are going to be some days when the pool
water temp will be below the air temp. But look at it
from this perspective. If the system works to do what
is wanted, then the pool should be 80+, no? Isn't that
a purpose of the pool heater? So, if the water is 80 - 85,
reagardless of how it gets there, I don't see that as being
a big difference versus the ambient air if you average
it out. For example, at night, the pool at times could
actually be above the ambient air temp, right?
If you;re saying, well the pool could be 75 and the
ambient air 90, sure I could see that, but that situation
has to be an exception, or else the thing isn't heating
the pool enough, right? If it's working, then you
should have 90 air, 85 water.

I have no delusion that this thing heats the pool to any significant
temperature.

But the main point of the whole TOH project was to
heat the pool. That was the original problem, not that
they wanted to lower the AC bill. The lowering of the
AC bill was an additional benefit.

TOH never said heating the pool was the _main_ point at least I didn't
catch it. Maybe they mentioned pool heating first?

I think they were wrong to mention pool heating at all because
this isn't going to heat the pool enough to make a difference.

I'm in central NJ (like you).

I didn't see where they mentioned the location of the house in question but
since it's TOH, it's likely it's New England. Like us in NJ, only
worse. With the trees that guy had next to the pool, that water must be
freezing. Reminds me of swimming in the cold clear lakes of New
England. Nice water but cold, cold, cold.

 

[trader4]

I have no delusion that this thing heats the pool to any significant
temperature.



TOH never said heating the pool was the _main_ point at least I didn't
catch it.  Maybe they mentioned pool heating first?

Yes, that's how it started. TOH plumber, Richard T meets the
homeowner and the discussion is about heating the pool.
The HO says it's been hard keeping
the pool warm enough, the backyard is shady, that he has researched
other pool heating systems, wood burning, solar, hasn't got a roof
with exposure for solar, etc. Richard adds the benefit of making
the AC
more efficient when he describes to the HO how the thing works.

And then to confuse things even more, Richard also says
that the AC will use the same electricity as before, but
you'll be getting heat for the pool too. So, which is it? That
it improves the efficiency of the AC, or not? I think it
does. One thing I think everyone agrees on is that when
the pool is heating you could turn off the AC condenser fan.
That for sure saves money. But, I wonder if they even do
that? It would save energy, but it would also complicate the
install because now you have to modify the AC equipment
to selectively kill the fan. What about things like AC
warranty? What about that for the system anyway?
I mean if say the compressor fails, what if Trane says
the system was modified, screw you? Maybe that
wouldn't happen, because the servicing company would
just put it in as a warranty claim anyway.....

I think they were wrong to mention pool heating at all because
this isn't going to heat the pool enough to make a difference.

I'm in central NJ (like you).

I didn't see where they mentioned the location of the house in question but
since it's TOH, it's likely it's New England.  Like us in NJ, only
worse.  With the trees that guy had next to the pool, that water must be
freezing.  Reminds me of swimming in the cold clear lakes of New
England.  Nice water but cold, cold, cold.

Yeah, I was wondering where it was located too. I came to the
same conclusion, that it was probably NE.

The big thing missing here is any report on how well it worked.
You would think they would come back after a week to
see the results. I don't doubt that it will heat the pool some.
The real question is whether it's enough to make the
whole thing worthwhile.

I think we're on the same page with regard to that. Around
here a typical inground pool has a 200K to 400K btu heater.
And if you've used one, you know that it takes it many hours
running full blast to heat the thing. With say a 3 or 4 ton AC,
you're getting what, 45K maybe 55K btus? And most of
the time the typical AC is not running anywhere near constant.
Mine on typical summer days runs maybe 25% of the time,
from 11am until 8pm or so. And very little at night.
So, you get it part time.

 

[JOJO]

This is a great item. Its relatively easy to install and it augments our solar heater very well.
We live in Florida and like to keep our pool around 89 - 91 degrees all year round. The air conditioner in most homes in Florida runs all year round.
In the winter with no heating at all, pools around here dip to about 70 degrees. With the solar heater running in the winter it brings it up maybe 10 - 15 degrees. Unfortunately cool nights bring the temp right down again, there for the electric heater has to fire up pretty much all night long just to bring it up 7-10 degrees to augment the solar heaters. So a morning swim is out of the question.
Now with the combination of this AC exchanger and the Solar heater the pool is keeped near 90 degrees without having the electric heater ever turn on. It is a savings of about $250 -$300 a month on our electric bill. That is a lot of savings.
One year with this addition and it's paid for it's self. That is not including the fact that the pool heater basically has no wear & tear on it, since it barely runs. And I'm sure the AC has less stress on it since it is being cooled more efficiently.

For us it's a win -win. Especially as we installed it our selves. just my 2 cents worth.