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Old 02-20-2012, 10:08 AM   #1
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Suggestions for heating a swimming pool


I am looking for suggestions on the best way to heat an inground swimming pool in northern NJ. It is 20,000 gallons with vinyl liner and foam under the liner. The pool gets fairly good sun and I always have a solar cover on it when not in use. For the last 10 years I used 5 4x8 solar panels from SolarDirect on the roof. It was a decent system that gave me a rise of about 1 degree per hour between noon and 6 for a max of 6 degrees per day as long as you have good sun that day. I removed the solar panels last year to install a new roof. I now have to decide wheather to re-install the panels or possibly go with a gas heater or heat pump. Biggest advantage of the panels is that it's cheap. Some cons are you can only get a max of 6 degrees per day (and that's with good sun) and you can never plan when the sun is going to be out. So if you have a party planned and have a few cloudy days your stuck. Also the roof becomes a little cluttered and I never did like pumping 20,000 gallons of water up there and worrying about some kind of connection failure up there. I am thinking about a 200K BTU natural gas heater which should give me about 1 degree per hour rise rain, shine or darkness or maybe a heat pump. This way everything is more compact and on the ground but more expensive. Any thoughts or ideas? I would love to hear from those with a heat pump. There are a lot of marketing claims about how good they are.

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Old 02-20-2012, 12:08 PM   #2
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Suggestions for heating a swimming pool


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I am looking for suggestions on the best way to heat an inground swimming pool in northern NJ. It is 20,000 gallons with vinyl liner and foam under the liner. The pool gets fairly good sun and I always have a solar cover on it when not in use. For the last 10 years I used 5 4x8 solar panels from SolarDirect on the roof. It was a decent system that gave me a rise of about 1 degree per hour between noon and 6 for a max of 6 degrees per day as long as you have good sun that day. I removed the solar panels last year to install a new roof. I now have to decide wheather to re-install the panels or possibly go with a gas heater or heat pump. Biggest advantage of the panels is that it's cheap. Some cons are you can only get a max of 6 degrees per day (and that's with good sun) and you can never plan when the sun is going to be out. So if you have a party planned and have a few cloudy days your stuck. Also the roof becomes a little cluttered and I never did like pumping 20,000 gallons of water up there and worrying about some kind of connection failure up there. I am thinking about a 200K BTU natural gas heater which should give me about 1 degree per hour rise rain, shine or darkness or maybe a heat pump. This way everything is more compact and on the ground but more expensive. Any thoughts or ideas? I would love to hear from those with a heat pump. There are a lot of marketing claims about how good they are.
20,000 gals x 8.3 lbs/gal needs ~170,000 BTU for a 1F rise.
How long do you want to wait to get to your final water temp? This time depends on the heat capacity of the water and the ground temp. The (temp rise)/time curve will be exponential.

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Old 02-20-2012, 12:27 PM   #3
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Suggestions for heating a swimming pool


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20,000 gals x 8.3 lbs/gal needs ~170,000 BTU for a 1F rise.
How long do you want to wait to get to your final water temp? This time depends on the heat capacity of the water and the ground temp. The (temp rise)/time curve will be exponential.
20,000 gals x 8.31lbs/gal = 166,200 BTU for a 1F rise. So a 200,000 BTU gas heater at 85% efficiency = 170,000 BTU. The math works out. Even have a little extra for the loss.
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Old 02-20-2012, 12:40 PM   #4
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Suggestions for heating a swimming pool


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20,000 gals x 8.31lbs/gal = 166,200 BTU for a 1F rise. So a 200,000 BTU gas heater at 85% efficiency = 170,000 BTU. The math works out. Even have a little extra for the loss.
And there may be a substantial loss through the concrete. If you know the thickness and surface area of the pool bottom we can figure this in.
Look before you leap.

I spent some time in Leonia (not bad) and Jersey City (back then, awful) and Paterson (back then, awful).

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Old 02-20-2012, 12:56 PM   #5
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Suggestions for heating a swimming pool


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And there may be a substantial loss through the concrete. If you know the thickness and surface area of the pool bottom we can figure this in.
Look before you leap.

I spent some time in Leonia (not bad) and Jersey City (back then, awful) and Paterson (back then, awful).
Vinyl lined pool with foam and vermiculite under the vinyl. This should provide some level of insulation. I don't think I had that great of heat loss in my years of using the solar panels but again this is hard to determine.
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Old 02-20-2012, 01:43 PM   #6
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Suggestions for heating a swimming pool


If the pool is empty you may be able to measure heat loss by putting small quantities of heated water into the pool.

This whole thermal circuit may be not so hard to figure out, using an analogy of a capacitor being charged by a current source.
i = C dV/dT, where i, the current, is the BTU/hr input to the pool minus the heat loss through pool bottom, C is the heat capacity of the 20,000 gals, V is the capacitor voltage (water temp) and T is time.
In this case the temp. increase is linear with time, it's a ramp.

Last edited by Yoyizit; 02-20-2012 at 01:46 PM.
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Old 02-20-2012, 01:47 PM   #7
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Suggestions for heating a swimming pool


Yes but that will only give initial heat loss. Once the pool is warmed up, the insulation is warmed and the ground around it somewhat warmed the loss goes way down. I really don't think it's worth checking being that I have been heating fine for years. Most of my loss comes at night if I leave the cover off.

Last edited by mpnret; 02-20-2012 at 01:49 PM.
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Old 02-21-2012, 11:37 AM   #8
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Suggestions for heating a swimming pool


Yes.
http://x.havuz.org/viewtopic.php?p=31653
Supposedly heat is only lost by radiation, convection or conduction, but water evaporating must cool the remaining water and since the water lost must be replaced by cold water this is kind of a roundabout heat loss method.
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Old 02-21-2012, 04:18 PM   #9
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Suggestions for heating a swimming pool


200,000 to 250,000 BTU gas fired heater is plenty for a 20,000 gallon pool. But you should maintain temp close to what you want, and not let it drop too low.
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Old 02-21-2012, 05:56 PM   #10
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82F, right?
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Old 02-21-2012, 06:14 PM   #11
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Average of 82. A lot prefer 84.
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Old 02-22-2012, 08:46 AM   #12
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Suggestions for heating a swimming pool


I don't have a pool so this is pretty novel to me.

With this pool you can go from 50F to 84F in 34 hours at 170,000 BTU/hr and if you want hot water in 3 hours you need 1.7 million BTU/hr and once you get the water to 84F very little heat input will maintain it.

Does anybody have a link to pool heater prices? Does anybody reclaim the considerable amount of heat stored in the water and use it to heat the house?
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Old 02-22-2012, 09:11 AM   #13
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Suggestions for heating a swimming pool


I never had to heat a pool from 50 to 84 and hopefully never will. During the entire swimming season my pool water remains high 70's to mid 80's with just the solar cover on it. The main purpose of the heater is to give a few degree bump during those lower temps, usually after a few cloudy days. Those who are looking to swim during the off season may have a greater need. A heater with a 1 degree/hour rise is ideal for me. As far as a link to pool heater prices goes, just google pool heater and you will have all the links you want. Figure $1500 - $1700 for a 200K unit which will give you the 170K when you allow for effieiency loss. During the off season, which is when we heat the house, pool water is frozen on top and very cold at the bottom. So not much heat to reclaim.

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