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Thread: Geothermal pool heating

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    EvilTwin's Avatar
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    Geothermal pool heating

    Not sure if this is the right subforum for this question, so if the wrong place, please feel free to move it.

    I have a geothermal heating system in my home. I would like to find a way to utilize the output of my heat pump to send the heat through a heat exchanger that will put the heat into the pool before sending it out to the rest of my ground loop. I have seen a number of things like plate heat exchangers and such, but I was wondering if anyone has any practical experience with such a thing. It seems like an easy concept. My heat pump cools the house in the summer by removing heat from the air. So why not feed that heat into my pool to maintain the temp I like and then send the rest of the heat into the ground as usual and keep from having to use a ton of propane. Any thoughts?
    ----------------------------------------------------
    25000 (?) gallon Plaster IG roman-end pool (18x36, give or take, 8 ft deep end), 7 ft round spa-spillover to pool
    Nautilis FNS-48 DE Filter, disconnected separation tank
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    Mod Squad pooldv's Avatar
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    Re: Geothermal pool heating

    Hey, I think that is a great idea! I also have a 5 ton geothermal heat pump system with 5 wells for the house and would love to move that "free" heat into my pool instead of the ground. Haven't spent a lot of time trying to figure that out because I am nervous about messing up a system that works great for the house. Also, I believe my well temps tend to be about 72* and I need my pool more like 85+, but I don't know what the water temp is exiting the heat pump. But, if some genius comes along to this thread and tells us how awesome it is then I would love to hear all about it.
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    Re: Geothermal pool heating

    http://www.amazon.com/Titanium-Water.../dp/B00B1GVBR8

    Don't have any idea of the practicality, though I have considered it.
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    Re: Geothermal pool heating

    Geothermal heat (and cooling) can work for swimming pools. The main thing to keep in mind is that the swimming pool needs significantly more heat than your entire house does. To be really useful the geothermal system would need to be sized significantly larger than what you need for your house. Expanding those system tends to get expensive.

    Without the geothermal aspect, taking waste heat out of the house and putting it into the pool is possible, but it tends to be a bad match in most situations. Peak cooling is mid-summer, at which point the pool is normally just fine without extra heat. While early in the spring and late fall, when the pool needs lots and lots of heat, the house only needs a little air conditioning. If you live far enough north that the pool needs heat even mid-summer, it can be a better fit.
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    Re: Geothermal pool heating

    Thanks for the comments, Jason. While I certainly would not expect to be able to dump a massive amount of heat into the pool, I figure any amount of heat would help. I, too, have a 5 ton geo unit. I'll need to look at my system data and see what the exit water temps get up to. If there is a good enough delta between that and the pool temp, it might not be a bad idea. I've seen a number of water/water heat exchangers out there, like the one listed above or some other plate exchangers. I was just hoping someone maybe already tried it.
    ----------------------------------------------------
    25000 (?) gallon Plaster IG roman-end pool (18x36, give or take, 8 ft deep end), 7 ft round spa-spillover to pool
    Nautilis FNS-48 DE Filter, disconnected separation tank
    1.5HP single speed main pump. 3/4 HP pressure-side cleaner pump.

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    Re: Geothermal pool heating

    The main thing to keep in mind is that the swimming pool needs significantly more heat than your entire house does.
    Perhaps 20 times as much. Heating a pool is a huge energy transfer......I learned (and failed) the hard way.
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    Re: Geothermal pool heating

    I can understand people wanting to spend the least amount of $$ on things like heating a pool but so many times the way to go about it is still the traditional way with purchasing products designed to do the task.

    Geothermal is great for your house needs but outside of that it is not the best choice for heating a pool. If it were then everyone would be jumping on the bandwagon and doing it. Sticking with products made/designed for pool heating is the only way to go.
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    Mod Squad JohnT's Avatar
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    Re: Geothermal pool heating

    You need to realize that this application is about dumping waste heat from cooling the house into the pool rather than running it just to heat the pool. There is essentially no cost to running such a system into the pool other than the investment in the heat exchanger. The system has to dump the heat somewhere, so it's either in the pool or in the ground. My system heats almost all of my domestic hot water at no cost from May to September. The only thing that keeps it from doing all the heating is that it can't quite get it hot enough.

    Quote Originally Posted by ps0303 View Post
    I can understand people wanting to spend the least amount of $$ on things like heating a pool but so many times the way to go about it is still the traditional way with purchasing products designed to do the task.

    Geothermal is great for your house needs but outside of that it is not the best choice for heating a pool. If it were then everyone would be jumping on the bandwagon and doing it. Sticking with products made/designed for pool heating is the only way to go.
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    Re: Geothermal pool heating

    In nearly all cases, there simply isn't enough waste heat available to justify the fairly high up front cost of a suitable heat exchanger. If geothermal systems were more popular, and the right kind of heat exchanger was mass produced, it would be more attractive, but it would still be marginal in terms of lifetime cost compared to a more conventional heat source.

    The temperature difference is going to be small, which means a fairly complex system, probably a heat pump, just for the pool heat exchanger. And the excess heat availability doesn't match up at all well with the need for pool heat. Add in that this is going to be a small market, and small production runs mean higher prices.

    We might see this someday. Heat pumps are getting less expensive, geothermal is getting more popular, and energy for conventional heating is getting more expensive. Given a decade, or perhaps several decades, I can see this becoming practical, but right now it just doesn't make sense in most climates.
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    Re: Geothermal pool heating

    Quote Originally Posted by JohnT View Post
    You need to realize that this application is about dumping waste heat from cooling the house into the pool rather than running it just to heat the pool. There is essentially no cost to running such a system into the pool other than the investment in the heat exchanger. The system has to dump the heat somewhere, so it's either in the pool or in the ground. My system heats almost all of my domestic hot water at no cost from May to September. The only thing that keeps it from doing all the heating is that it can't quite get it hot enough.
    And this is really what I am thinking. I don't expect the geo to do all the work, but if it does some of the work, that's less that I pay for propane and it's even green, if you like that sort of thing. I have a 300,000 BTU propane heater on the pool. It's brand new and since I have a spa, I need it, regardless of what other heat I may want to employ, like solar. None of those will heat a spa in the time I would like. But a heat exchanger takes heat I would dump into the ground and dumps it in the pool instead. Just seemed like a good idea.
    ----------------------------------------------------
    25000 (?) gallon Plaster IG roman-end pool (18x36, give or take, 8 ft deep end), 7 ft round spa-spillover to pool
    Nautilis FNS-48 DE Filter, disconnected separation tank
    1.5HP single speed main pump. 3/4 HP pressure-side cleaner pump.

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    Re: Geothermal pool heating

    I also installed a 5 ton geothermal heating/cooling unit for my approx 3500 sqft home in Delaware after we moved here from NY 10 yrs ago. It is an open loop system with a variable-speed well pump that sends about 19 gpm of 56 F groundwater through the unit. Is saving me now thousands as propane in DE is very expensive - but initial cost was high. In AC mode this source water returns to the discharge well at about 65 F. Even if I cut the flow temperature would only be about 70s and the unit would run longer - not as efficiently. But I also installed a 12x24 Intex UltraFrame pool outside last year and are in the process of installing a 100,000 BTU Aquacal WS05 geothermal water/water pool heatpump now which I expect to recapture much of the home's waste heat by running the water from the home heatpump in series through this Aquacal unit - so my pool water can easily be in the mid 80s - I found I was not using the pool much when water was below 78 F. Kids don't mind - but at my advanced age I like 82+. In LI NY I once had bought a home with a 22,000 gal indoor gunite pool and had self-installed a tube in tube heat exchanger that used the hot freon gas from a 4-ton Central air unit to heat that pool - it worked great - the home AC had much lower head pressure and pool during the AC season was mid 80s - but I am an engineer and could calculate the system and installed it myself. It worked for about 20+ years until we sold the home to retire. Note: Indoor pools absolutely need an automatic pool cover for humidity control in any case - and such automatic covers greatly reduce most heat loss. If only I could buy such cover for my Intex pool at a reasonable price? Have a wooden deck all-around, easy to install the tracks for the cover.
    Will try to write about this "unusual Intex pool project" when more time. To make sure this Ultra-Frame pool was and stayed absolutely level (a must) I first built a heavy-duty 5" concrete patio - even if a future buyer of our house does not want a pool - they have the benefit of a large 22x40 concrete patio.

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    EvilTwin's Avatar
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    Re: Geothermal pool heating

    Quote Originally Posted by Geobioheating View Post
    I also installed a 5 ton geothermal heating/cooling unit for my approx 3500 sqft home in Delaware after we moved here from NY 10 yrs ago. It is an open loop system with a variable-speed well pump that sends about 19 gpm of 56 F groundwater through the unit. Is saving me now thousands as propane in DE is very expensive - but initial cost was high. In AC mode this source water returns to the discharge well at about 65 F. Even if I cut the flow temperature would only be about 70s and the unit would run longer - not as efficiently. But I also installed a 12x24 Intex UltraFrame pool outside last year and are in the process of installing a 100,000 BTU Aquacal WS05 geothermal water/water pool heatpump now which I expect to recapture much of the home's waste heat by running the water from the home heatpump in series through this Aquacal unit - so my pool water can easily be in the mid 80s - I found I was not using the pool much when water was below 78 F. Kids don't mind - but at my advanced age I like 82+. In LI NY I once had bought a home with a 22,000 gal indoor gunite pool and had self-installed a tube in tube heat exchanger that used the hot freon gas from a 4-ton Central air unit to heat that pool - it worked great - the home AC had much lower head pressure and pool during the AC season was mid 80s - but I am an engineer and could calculate the system and installed it myself. It worked for about 20+ years until we sold the home to retire. Note: Indoor pools absolutely need an automatic pool cover for humidity control in any case - and such automatic covers greatly reduce most heat loss. If only I could buy such cover for my Intex pool at a reasonable price? Have a wooden deck all-around, easy to install the tracks for the cover.
    Will try to write about this "unusual Intex pool project" when more time. To make sure this Ultra-Frame pool was and stayed absolutely level (a must) I first built a heavy-duty 5" concrete patio - even if a future buyer of our house does not want a pool - they have the benefit of a large 22x40 concrete patio.
    Thanks for that info. I went back and looked at the data that I have been capturing from my system since it was installed last summer. My exit water temp (EWT) was rarely, if ever, above the mid-80's. I, too, like water in the low 80's, so it would be really hard to get a lot of heat out of my loop to dump into the pool. I like your idea with the pool heat pump in series. Given your open loop and feeding that loop water into another HP, you will be able to extract much more heat than just a simple heat exchanger. Best of luck with that.
    ----------------------------------------------------
    25000 (?) gallon Plaster IG roman-end pool (18x36, give or take, 8 ft deep end), 7 ft round spa-spillover to pool
    Nautilis FNS-48 DE Filter, disconnected separation tank
    1.5HP single speed main pump. 3/4 HP pressure-side cleaner pump.

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