"Ryan" wrote in message
...
roughly 26,000 gallons. I also have a garden variety AC, it is a 2.5
ton
unit. My question is this, could I use a water cooled heat exchanger as
opposed to the standard over-head fan air-cooled condenser? The water
would
be chlorinated pool water. It seems to me that I could kill two birds
with
one stone here. I mean the A/C and the pool pump are going to be
running
anyway, why not give it a try? I know that the temp gain from a 2.5 ton
unit won't be that much, maybe a few degrees per day, but what the heck,
I
am just wasting the heat now (as if summer air needs to be any hotter).


I too own a pool and have been considering an approach to this idea for
some time now.

The best temperatures my pool reaches are 75-78 degrees in the hottest
part of the summer. To me, this is ok, but often too chilly, especially
for night swims, which I love. I would not have a problem with the
water being to warm, even if, it is all to easy make a pool cooler.

I've perused groups like this one for several months, and it is clear
that everyone is ready to tell you how expensive it *has* to be and how
it won't work. I've seen no commercial off-the-shelf units that are
specialized for this purpose.

If you wish to implement something, I think you will have to invent it
an install it on your own.

Here are some of my thoughts on design:

Ideally this is accomplished with minimal or absolutely no material
changes to your existing air conditioning unit.

I would not, as others have suggested, abondon the air-cooling portion
of the condenser radiator. I would never want to rely on the pool water
to be the only way to cool the AC refridgerant in the first place. This
would be begging and pleading for trouble.

In a perfect world, a radiator or big block of metal like copper or
aluminium would be used. Inside this would be two plumbing networks.
One with Freon/Puron and the other with H20. This would be the most
efficient method I could imagine for heat transfer. A few potential
problems though... Coolant temperature can be hot! - over the boiling
point of water. So this system would need to have water flowing through
so quickly that it never boils, lack enough efficiency so it never
boils, or permits this to happen by being open ended, or with pressure
relief integrated.

This is complicated by the fact that it needs NOT to be the only way to
cool the refridgerant. Keep in mind, unless you are a blasted engineer
doing a lot of careful professional design here, you're playing with
fire. That kind of heat exchanger, considering the pressures involved,
just isn't feasible anyway. It would be nice to have this
liquid-to-liquid system in line before the liquid-to-air network. This
way you get first dibs at the heat, but if the system is empty of water,
it proceeds on as usual and the system works (although with a hot chunk
of metal sitting there).

So...

That idea sounds good on paper. It is efficient, and barring some
smaller details (I don't want to write a whole book here) it seems like
it could work.

We need something simpler and cheaper.

I've long mourned the loss of the idea of a liquid-to-liquid heat
transfer system because of its efficiency. I have pondered the idea of
running a copper water pipe alongside and within the insulation of the
refridgerant pipe leading into the evaporator. It would take a big run
to make much difference and even at that, I couldn't imagine efficiency
being very good.

A simpler, cheaper and not very efficient design would be to place a
standard radiator above the fan of an existing AC unit. I would think
12-18 inches would be as close as you would want to get. You don't want
to impede the air flow at all because that fan and that air has an
important job to do. Since this is hot air, it heats our water and we
are making some use of the byproduct of the AC unit. It doesn't help
the efficiency of the unit.

We don't have to care too much that it isn't very efficient because it
is cheap, and at least it is something. This radiator could be as
simple as one out of an old car. Yes it is aluminum and yes chlorine
will react with it (gasp!) but you can find these thing for cheap to
nothing in price and exchange them out.

This introduces another problem. I would never want to pipe my pool
water out and over and around some place under my yard, and so forth.
I've lost the pool once or twice due to plumbing defects and the last
thing I want is to introduce a high probability of this happening again.
Therefore, instead of this design

heat ----------- pool water

I would consider one my like they use at modern nuclear power plants to
protect their coolant water

heat -------- coolant water ----------- pool water

In this design, I would have to add another heat exchanging device. The
water would be clean (non acidic) and would circulate through the
radiator and get warm. I would have to install a radiator and either
immerse it into the pool water itelf (safest, no leaking option) or
contrive a liquid-to-liquid thermal transfer system (like referenced
above) and pump both water sources through it. Now my circulating water
system would be only 20-50 gallons at most and if it fails, I don't lose
$100 of pool water (plus chemicals). Again, adding another piece here
means less efficiency, however without doing it, I have no idea how
much. Consider also, that your pipes had better be well insulated. In
my case, it would be about a 100 foot run of pipe. Considering flow
rates would be pretty low, I've got to take insulation seriously in
order to realize any heat at the pool. If I am not mistaken, chlorine
bothers PVC as well as most other plumbing options (it is acid, after
all), but it holds up for a pretty long time. You'd better blow them
out for the winter.


So there are a few things to consider and seeing as how it can get
complicated, I think this is why nobody has any first hand knowledge of
it and nobody is selling anything to do it. Depending on your style
and what you used, I think you could set up a basic system pretty
cheaply. (At minimum a radiator, a few sticks of PVC and use the pool
pump's pressure and then upgrade from there if it works)

I'd love to hear others' thoughts on the topic.

Arizona Public Service used to sell a thing called "Hot Tap" "Get hot water
from cold air" A huge ad campaign followed the interduction of these heat
exchangers. APS pulled them off the market in less than 6 months. Water was
leaking into the a/c compressors and the would fail. This exchanger was
copper to copper using city water.
Copper and pool water will not last very long. Do some googling before you
destroy your a/c compressor.
Or change your pool over to an natural pool with out chlorine. Fish and
plants in the water usually on one end or in a cove built for them.
Good luck and keep us posted on your project. It would be cool for the
little guy to win for a change.