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Thread: Installing pool water heat exchanger in HVAC

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    Installing pool water heat exchanger in HVAC

    Anyone installed a pool water heat exchanger in line with their HVAC refrigerant condensor? There is a company on the east coast that does this and I'm curious as to the experience of anyone that has it installed.

    I'm planning to install a heat exchanger in my system which is right beside my pool equipment. I want to use it to lower my AC bills during the months that the pool is not in use. I expect it may extend my pool swimming season by warming the pool. I also expect nothing but electrical efficiency gains as I'll use the AC control to switch on the pool pump. AC run time will be used for pool filter time.
    16 x 32 IG Vinyl
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    Mix,

    Welcome to the forum. Interesting post but I can't quite follow your idea. I have some experience with both water-to-air and water-to-water exchangers so I can't quite figure out how your trying to use the exchanger. Could you elaborate?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Dave,

    I should have been clearer.

    My thought is to use a refrigerant to water heat exchanger. There is an example here: http://www.packless.com/heat%20exchrs/heatexch.html for a heat exchanger or simply use a chiller/evaporator coil setup like these http://www.packless.com/chiller/chevaps.html. Note that I am in no way affiliated with the referenced company. This was just an example that I found in my internet search. So, I cannot vouch for the quality/efficacy of the referenced products.

    So, I am planning to tap into the evaporator after the compressor while the freon is in liquid form and pass it through the water-refrigerant heat exchanger. The output of the freon liquid will reconnect into the original AC line. Think of the exchanger as a serial supplement to the air-refrigerant exchange that is already a part of the AC unit. The pool pump will be wire OR'd to the original timer and the AC compressor control relay to ensure it turns on any time the AC compressor is on.

    I do know that I will need a freeze sensor in the interior to protect against icing of the internal coil as I'll be pulling a lot of heat out of the line in cooler months.
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    Now I understand...Thanks.

    While I have no experience with that application (and I really like the idea), two thoughts come to mind that I don't know the answer to:

    1. Will the resultant temperature drop in the freon have any negative effect as it unpressurizes and turns to gas?

    2. Secondly, will you be able to pull off enough btu's to make it worthwhile? I heat my pool with a wood-burning non-pressurized boiler. My water-to-water exchanger is incredibly efficient but I am stunned at the btu input required to have any effect on my pool. Granted, I have a large pool but my 200k wood burner can barely dent the pool water temp running in full forced-air mode. My setup made me realize why commercial pool heaters kick out so much btu (read...money). You need a VERY large btu input to move your pool water temp even the slightest bit.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Quote Originally Posted by duraleigh
    Now I understand...Thanks.

    While I have no experience with that application (and I really like the idea), two thoughts come to mind that I don't know the answer to:

    1. Will the resultant temperature drop in the freon have any negative effect as it unpressurizes and turns to gas?

    2. Secondly, will you be able to pull off enough btu's to make it worthwhile? I heat my pool with a wood-burning non-pressurized boiler. My water-to-water exchanger is incredibly efficient but I am stunned at the btu input required to have any effect on my pool. Granted, I have a large pool but my 200k wood burner can barely dent the pool water temp running in full forced-air mode. My setup made me realize why commercial pool heaters kick out so much btu (read...money). You need a VERY large btu input to move your pool water temp even the slightest bit.
    i have a pool comprable to yours, i want to add a heater, do you think i whould have to go all the way to a 400,000k to get anyware,
    also, another question i see here, if i understand your question right, if you want to tie it in with your home unit wouldn't heating the pool be heating the house too, i need heat in june for the pool. but in june here its 90 degrees in the shade, so i need to cool the house, that would not work at all if you ask me.

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    I'm pretty sure that any additional means to remove latent heat from the refrigerant is a good thing. It will actually increase the efficiency of the AC. Well, as long as it's on the condenser side
    I don't know about that particular exchanger, but I can't see why it shouldn't work fairly well.

    When I was living in Florida, my house had what was called a HRU, or Heat Recovery Unit installed in the heat pump refrigerant line (between the compressor and the condenser), and was plumbed into the water heater in a loop from the hot water outlet to a fitting inserted behind the drain valve. Whenever the air conditioner ran, it heated water and pumped through into the water heater. Naturally, in Florida, the AC ran a lot - I kept the water heater breaker off pretty much all summer long. It was a model very similar to some of these: http://trevormartin.com/hru.asp.

    The premise of an air conditioner is to remove heat from inside, and transfer it away outside. Anything that helps these transfers is a good thing.
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    look into desuperheaters. Most can be installed quite easily into your AC system. The only downside with them is that most of the exchangers are made to heat potable water and may not last long if your water chemistry is off.
    ~Megan

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    Ohm Boy, yes, thanks for pointing out the condensor is the side to tap

    Thunder, keep in mind that the refrigerant at the condensor is approaching 200 degrees F. It's after it has had some of the heat pulled out and pressure dropped that it is cool. Even if your pool is already over 80 degrees it would work great as a heat sink at this stage.

    Thanks all for the inputs! I'll work on this and provide an update once it's installed and working (hopefully).
    16 x 32 IG Vinyl
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    That looks like a very interesting idea to apply to an existing system. I am in the process of working out the details on a similiar idea. However, my house has a water source heat pump installed using an open loop design connected to my well and returning to the ground. What I am going to do is to connect it inline with the pool pump/filter circuit and try to use the pool as a heat sink. I figure it may possibly heat the pool too much in the hottest summer months of July thru August so I may have to switch back to the well during that time. But the low cost of connecting it into the system makes it worthwhile to give it a try. I will report back on how well it works, but it wont be for a couple of months.
    Michiele
    Newbie pool owner
    25,000 gallon inground, vinyl lined pool, sand filter

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    I’ve thought of this idea also, I stand outside next to my heatpump and it’s pumping ice cold air, while my AC units are next to it blowing hot air to cool off the coils, I just think, what a waste of energy. I was thinking a commercial water chiller would work, with a cold water loop going to an exchanger inside and a hot water loop would go to an exchanger for the pool water. I’d need one small enough for my application, replacing 3 A/C units and 1 heat pump, and something I can afford.

    I’d be interested to hear how well an exchanger attached after the compressor works. I’d think the AC would cycle far too often, forcing your pool pump to come on and off far more than normal, reducing its lifespan.
    Gary
    21k gal SW, IG Gunite PebbleSheen, 1HP Jandy, Jandy 340 filter, Polaris 280, 17' fiberglass slide w/ 2HP pump.

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    For me, my well pump cycles very often to keep up with the heat pump. But the unit works very efficently because its much easier to make cold air when you are using 72 degree well water. It doesnt bother me that the pool pump will cycle more because it is easier and cheaper to replace the pool pump than the well pump. Besides, it is all experimental at this point and other than a little plumbing it wont cost much to hook it up.
    Michiele
    Newbie pool owner
    25,000 gallon inground, vinyl lined pool, sand filter

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    Ohm_Boy's Avatar
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    Quote Originally Posted by crabboy
    I’ve thought of this idea also, I stand outside next to my heatpump and it’s pumping ice cold air, while my AC units are next to it blowing hot air to cool off the coils, I just think, what a waste of energy. I was thinking a commercial water chiller would work, with a cold water loop going to an exchanger inside and a hot water loop would go to an exchanger for the pool water. I’d need one small enough for my application, replacing 3 A/C units and 1 heat pump, and something I can afford.

    I’d be interested to hear how well an exchanger attached after the compressor works. I’d think the AC would cycle far too often, forcing your pool pump to come on and off far more than normal, reducing its lifespan.
    I wouldn't suppose the pool pump would have to run whenever the AC was running, you'd just end up w/ water at the same temp as the condenser inside the exchanger, and it would only circulate as convection allowed until the pump did kick in.
    You could just plumb in a small pump to do nothing but circulate the water when the AC was on.

    I have also seen commercial installations that used a pond for part of the cooling loop. You'd think that it was just a decorative pond w/ a fountain if you didn't know they were sinking building heat into it. That is, until the late or real early hours, when it's steaming all over the surface like a London waterfront.
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    I was thinking along a similar line. I have a pool waterfall which I'll use in the warmer months as the return to get the evaporative chilling effect so I don't over-heat my pool (hopefully).
    16 x 32 IG Vinyl
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    My water source heat pump has no outdoor unit, only the water/refrigerent heat exchanger so it has to have a constant source of water when it is operating. I want to add some type of fountain to help with evaporitive cooling. I am probably just going to use one of the floating ones you plug into a return for now. If I find that it is worth it, I may add a more permanent feature and a small pump just for the a/c. I have a 5hp submersible well pump that cycles when the a/c is on, so if I can drop back to 1/2 - 1hp pump instead I figure I should save a litlle energy.
    Michiele
    Newbie pool owner
    25,000 gallon inground, vinyl lined pool, sand filter

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    This sounds like a great idea if the economics work - i.e. the cost of the equipment. Let us know how much it costs and how it works for you.
    20x40 IG vinyl, heatpump and solar and 3 siberian huskies, 10kw PV solar electric system. Nikon Photographer D800e dSLR.

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    Re: Installing pool water heat exchanger in HVAC

    Bumping for more info. A company makes one now called a Hotspot FPH. I'm seriously considering buying, and know the principles of operation and it all makes sense, I'm just looking for a real review or input from others.

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    Re: Installing pool water heat exchanger in HVAC

    Quote Originally Posted by jtex84 View Post
    Bumping for more info. A company makes one now called a Hotspot FPH. I'm seriously considering buying, and know the principles of operation and it all makes sense, I'm just looking for a real review or input from others.

    We just bought a pool and are going to work on installing it really soon so I am beginning to research the best setup. This Old House did a short segment on this idea which I just happened to find this old thread on here during my research. Bumping this thread up to the top to see if anyone has tried hooking up their AC condenser to their pool and has experience (good or bad) to share.

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    Re: Installing pool water heat exchanger in HVAC

    It's not a question of if it will work its a question of does your A/C run long enough to heat your pool and does your pool pump run long enough to take advantage of the time your A/C is running. This device will work the same way as a off the shelf heat pump pool heater. The problem with using this approach is that when you really want heat in your pool during the cooler months of the year you wont be running your central A/C. Conversely when you are running your A/C the most during the summer you wont want all that extra heat in your pool. At the end of the day you will have spent a lot of money on a system that will probably leave you wanting for another heater. Look very carefully at the correlation between when you plan on needing heat for your pool and when you will actually be running your central A/C to generate that heat.
    Chuck-
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