Swimming pool heat - condenser desuperheater?

[a210]

Why wouldn't I want to add a desuperheater / coolant-to-water heat exchanger in line with my AC system to heat a swimming pool?

Why isn't this common already? Swimming pool heat pumps run $- yet I have an AC compressor 10 feet away that spews out hot air 335 days a year. In doing some web searches, I've found lots of "homebrew" solutions for this but nothing that looks very professionally done. Is there some risk of putting a desuperheater onto a standard AC system?

I understand that the middle of summer wouldn't be a great time to use it - but here in south florida we have PLENTY of days in the fall and spring where the AC is running at least 8 hours a day, but the swimming pool is still too cold to jump in... I am sure the situation is pretty common in other warm climates as well.

[Shophound]

Swimming pools in arid climates have two things that help them from becoming too warm in summer; night time radiant cooling and round the clock evaporative cooling. There is a wider range of temperatures between daily highs and nightly lows, and the dew points tend to stay low.

Not so in humid climates like Florida. The daily high and low temperatures are not very far apart, and elevated dew point temperatures slow evaporation from the pool surface considerably, which also reduces evaporative cooling. Depending on how much desuperheating is done, the pool water could get very warm, even in cooler weather if humidity levels stay high.

For the money one could spend installing a desuperheater, my money would go into the house itself to reduce heat transfer through the walls and ceiling. Reduce the load, reduce the cost, and increase comfort.

[Moose]

Have you looked @ a solar pool heater? In Florida, that should be a good bet.

[a210]

from the pool surface considerably, which also reduces evaporative cooling. Depending on how much desuperheating is done, the pool water could get very warm, even in cooler weather if humidity levels stay high.

For the money one could spend installing a desuperheater, my money would go into the house itself to reduce heat transfer through the walls and ceiling. Reduce the load, reduce the cost, and increase comfort.

Understood - but my assumption (please correct me if I'm wrong) is that in an application like this, the desuperheater would be a simple passive heat exchanger. "turning off" the heat would be as simple as diverting the pool water away from it. (which is how solar systems here work as well)

Solar is great but runs the risk of damaging the roof, especially in case of hurricanes. I have a pracatically constant heat source just sitting there, seems silly not to put it to better use...

The "heat pump" water heaters where they have a window shaker mounted to a 50 gallon tank got me thinking about it again.

[davo]

To get enough heat from your a/c, you need more then a de-superheater. The average pool is 13,000 gallons, and has a lot of evaporative losses due to large amounts of surface area.

To get enough heat, generally a full size condensing coil needs to be added. This greatly increases system charge. When water temps change, or water is deverted away from the water coil, there is no room for the excess refrigerant refrigerant pressures will swing wildly. The cure is adding a receiver (and more refrigerant). Then, to maintain water temp, the a/c will have to run, and you may have to over cool your home to heat the pool.

If you try to run the water coil and air coil in parallel, you run the risk of oil lagging in an idle coil.

I have removed many attempted systems, and none worked to customers satisfaction.

By the time you do all this, destroy your a/c's warranty, you have paid for a heater that will heat the pool more energy efficiently, with a warranty.

[a210]

To get enough heat from your a/c, you need more then a de-superheater. The average pool is 13,000 gallons, and has a lot of evaporative losses due to large amounts of surface area.

To get enough heat, generally a full size condensing coil needs to be added. This greatly increases system charge. When water temps change, or water is deverted away from the water coil, there is no room for the excess refrigerant refrigerant pressures will swing wildly.

If you try to run the water coil and air coil in parallel, you run the risk of oil lagging in an idle coil.


Now that's the kind of answer I was looking for. Just to restate so I'm sure I get it - a de-superheater would be a relatively non-invasive change and could be added in series with the existing condensing coil, but your experience is that the amount of heat collected from that kind of device wouldn't be enough to matter?

Understood where you're coming from, if a more invasive heat exchanger would have to be used, then the pool would always have to be available as the heatsink, and that wouldn't necessarily work out...

[beenthere]

A normal/regular pool heater heat pump. Can run all day heating the pool(or 2 or more days straight). To raise a pools temp a few degrees.

If your A/C for your house ran all day on a day when it was 75° outside. Your house would be an ice box. And your pool still wouldn't be warm.

A desuperheater on removes a small amount of heat from the refrigerant. So on a 5 ton A/C, you might only get 20,000 BTUs an hour on a 95° day(when you don't need to heat the pool).

To raise a pool that has 10,000 gallons of water in it 1°, it takes 82,200 BTUs(doesn't allow for evaporation, or heat loss to ground through sides of pool).

A pool heat pump puts all of it heat into the pool.

Your house only has so much heat in it. And only gains so much heat an hour.

[dbooksta]

If your A/C for your house ran all day on a day when it was 75° outside. Your house would be an ice box. And your pool still wouldn't be warm.

This thread (http://hvac-talk.com/vbb/showthread.php?t=542522) has a few geothermal pros saying the exact opposite: A swimming pool does not have enough capacity to support residential A/C!

I don't think that's right, since evaporative cooling increases capacity as the water temperature increases, and fountains or other aerators people like to run in pools can boost it further.

But I also don't understand why beenthere thinks desuperheaters are so inefficient. Ultimately a compressor dumps its heat somewhere. Why couldn't it get most of it into a water-exchanger instead of the air-exchanger most residential A/C uses?

[chuckcrj]

just take the fan out of your condensing unit and mount the condenser unit under water.:playing:

[mark beiser]

This thread (http://hvac-talk.com/vbb/showthread.php?t=542522) has a few geothermal pros saying the exact opposite: A swimming pool does not have enough capacity to support residential A/C!

Right, a swimming pool isn't a big enough heat sink for the full heat load of a house when the house has a high load on it.
Your desuperheater idea would only be using a small portion of the heat being removed from the home, at a time when the heat load on the home is relatively light, and the AC system has short run times.

Trying to heat the pool with a desuperheater off your AC would be about as effective as one of these: http://www.amazon.com/Made-500w-115v-Immersion-Heater/dp/B002065SEU

It would give you some heat into the pool, but not enough to do the job, or even enough to be worth the expense.

[tedkidd]

I think the point is the cooling needs of the home and the heating needs of the pool are unlikely to ever match up. Even if the loads were somewhat aligned, spring and fall the pool gets little heat and summer a lot. Just the opposite of how you want to heat a pool.