Repak heat pump sizing tool: fact or fiction?

[JayG]

Hi All,

I'm planning on switching from a propane heater to a heat pump next season. Before considering brands, I've been chewing on the question of how much heater do I need. I ran across this handy calculator from Raypak. http://roxwebdev01.pixelgate.net/gas_sizing/Raypak.php?appid=1

One inputs your zip code, surface area of the pool, depth, desired temperature, and the months you want to keep the pool open. There are variables such as: wind, shading, pool cover use, run time of the pump, $/kWh, etc. Of course, you then choose between their various heat pump options. It has been interesting to play with.

My first question is whether forum members with heat pumps can testify to the legitimacy of their calculator. If your experience fits with their numbers, I can trust it to figure out what combination of BTU, run time, pool cover use, etc to plan on.

My inputs were: 10528 zip; 1050 sq ft; 5' depth; 82°F desired temp; 65% sun; 1.5 mph wind; $0.23/kWh; and played with these variables: unit BTU; run time; pool cover use; and the addition of April and October to our pool open time (it would be nice to add a bit to our swim season here in the NE).

If it is to be believed, the Raypak calculator says that 113K BTU can get me 82° F in April and October if I run up to 24/day and use a solar pool cover. I can maintain 82°F in May, June, July, August, September without a cover if run time is not limited. Obviously, adding a cover in April, May, Sept, Oct. cuts the cost of heating dramatically. (That is my thinking: extend the season with a pool cover in the non-peak use months to allow weekend swims, evening laps after work, etc. But keep the cover off when every day is a potential swim day during peak season).

I guess my second question (kinda based on the first) is whether 113 k BTU is laughably small for a 1050 sq ft, 40k gallon pool? The next step up is ~133k BTU and beyond that Raypak (Rheem) has a 170k BTU commercial unit. The latter requires 3 phase wiring which would add even more cost.

Thoughts? Opinions?

I'm not wedded to Rheems/Raypak just because of their calculator, but they do seem to make a quality product. They also appear to be compatible with the Pentair and Hayward automation/controllers I'm considering. Any other brands to consider?

Cheers,

Jay

PS. Third question: do sell my propane heater on Craig's List or do I keep it on the pad along with the heat pump?

 

[kirbinster]

Sounds plausible. I have a 20 x 40 IG pool in NJ and open first week in April and run till mid October and have had a 85,000 BTU/Hr and until today it did just fine. Unlike a gas heater, you really run the thing all the time and don't get fast heat ups. If you use it correctly it should be good.

I say till today as mine just bit the big one after 20 years and I too am in the market for a new one. Any suggestions?

 

[JayG]

Sounds plausible. I have a 20 x 40 IG pool in NJ and open first week in April and run till mid October and have had a 85,000 BTU/Hr and until today it did just fine. Unlike a gas heater, you really run the thing all the time and don't get fast heat ups. If you use it correctly it should be good.

I say till today as mine just bit the big one after 20 years and I too am in the market for a new one. Any suggestions?

Sorry to hear about your loss...

OK, it is good to hear that you can make a heat pump work for a comparably sized pool. I have no idea about heat pump brands. I've heard good things about RayPak/Rheems, but no real world experience. Their lower BTU units actually have good efficiencies. The prices seem pretty reasonable as well. Perhaps those with more experience can chime in.

What brand did you have that ran 20 years?

 

[Pool Tool]

I don't know much about heat pumps, but I do know that to maintain the warm temperature you only need to consider the surface area of the pool. That's where all your heat loss occurs and why cover use, wind, humidity etc. play such a large role. Obviously, there is some heat loss through the sides and bottom but hey what model is perfect. Gas fired heaters are better at raising the temp of the water, where the total volume (40,000 gals) is the consideration. But a heat pump should maintain temps well.

I would keep your heater, possibly even hooked up for those intermittent large warmups in early spring, etc. Good luck.

 

[JayG]

I don't know much about heat pumps, but I do know that to maintain the warm temperature you only need to consider the surface area of the pool. That's where all your heat loss occurs and why cover use, wind, humidity etc. play such a large role. Obviously, there is some heat loss through the sides and bottom but hey what model is perfect. Gas fired heaters are better at raising the temp of the water, where the total volume (40,000 gals) is the consideration. But a heat pump should maintain temps well.

I would keep your heater, possibly even hooked up for those intermittent large warmups in early spring, etc. Good luck.

Thanks! Good advice. I will keep both the propane and the heat pump for at least one season to see if they can serve a complimentary role.

Not sure how I would set them up using a controller, but I'll look into it during the off season.

Cheers,

Jay