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I might be able to get a real good deal on a 70,000btu heat pump. It’s underpowered for my pool, IG 16x32, but will it do anything for me? I’m not looking for a lot for an increase in temp….maybe a couple degrees (10at the most would be nice). I am considering solar panels but lack the space to put them and the pump is about the same in cost.
Basic math indicates that in order for you to maintain 10 degrees, you're going to need to run your circulation pump at least 10 hrs per day, IF YOU USE A SOLAR COVER RELIGIOUSLY AT NIGHT!
Here's the math, in case you're interested.
16 x 32 x 4.5 avg depth x 7.5 gallons per cuft x 8.3 lbs/gal = 143,424 lbs of water.
For a 10 degree temperature rise: 143,424 x 10 = 1,434,240 btus needed
Time needed to attain 10 degrees: 1,434,240 btus / 70,000 btus/hrs = 20.5 hrs
With a solar cover, expect to lose 50% of the 10 degrees rise so that's how much you're going to need to put back in during the day.
So, if it takes 20.5 hrs to gain 10 degrees, it will need 10.25 hrs to gain back the 5 degrees.
Without a solar cover, expect to lose 75% of the 10 degrees, or 7.5, and now you're at more than 15 hrs/day to maintain your desired temperature.
50% loss with solar cover? That seems a bit steep to me. I live in NH, where our nights are pretty cold still (low 40's), and I lose a couple degrees over night (my water temp is in the mid 70's right now with my heat pump), but nothing even close to 50%.
I have no idea about that heat pump but just can't see them losing that much heat with a cover.
Yes. 50% is about correct.
It depends on what your normal water temperature would be without the heat pump. From there, how much degrees is it to the mid 70's, where you're at now?
You're also running your pump all night long right? If so, your heat pump is still running at night too, right? So, you heat loss overnight would not be 50%, as your heat pump is still running to heat the pool.
The 50% loss is with the pump off and uncovered.
A solar cover helps quite a bit and is about 20% loss.
OK, I see. Your original post said a 50% loss with the cover on. 20% seems right to me. After a few days of 80 degree temps. up here that prompted me to open the pool (and the kids to swim despite water temps. in the mid. 60's), it has been around 60 during the day and upper 30's at night (with one night of 28, yikes!). I run my heat pump from 9am to 9pm as there is no point in running it at night with those temps). I only bother to run it at all as it does take a few days to warm the water up to swimming temp. and since I already have it there I want to be ready for our next warm day.
So I would say that I have it raised 10 to 15 degrees over where it would be and lose 2 or 3 degrees of that each night with the cover on and the pump off, so the 20% is right on the money.
Thanks for the info guys. My solar cover is on all day and night when I don't use the pool and I always cover it at night. I don't run my pump at night but run it for about 12 hours a day.
Thanks again
That should be fine. I have an 85,000 BTU/Hr heatpump on my 20 x 40 IG pool and it works great.
BigStein,
my bad. I didn't catch that... sorry
Hey, no sweat. I sure wish the temps. would rise up here in NH so I could reduce my loss. It has actually only been in the 50's here this week (after a couple days of a week and a half ago). Looks like we may hit 70 again this week so I am sure the kids will be in the pool on those days.
I wish I could send some of this 80++ temps down here in Florida. But lucky me has to go out to the Pacific NW this week... about the same as what you've got in NH. It's coming...dont worry...its coming.
Maybe this is for another thread . . .
What is the difference between a heater and a heat pump? And what does a heat pump run on?
A heat pump is a type of heater. It runs on electricity, but wait. For each unit of energy you put in you get around 5 units of heat out. Thus, it is much more energy efficient than a gas or propane heater. They are typically sized smaller than a gas heater, so you don't get rapid temperature rise with them - but once you raise the temperature they will maintain it very well. The only heater that is less costly to run is solar.
Might be (is) a dumb question, but how do heat pumps raise the water temp higher than the outside air temp? And I would assume that they heat better the hotter it is outside?
Yes the hotter it is outside the better they work. But think of it this way, how does an airconditioner make the inside air colder than the outside air? The answer is the same for a heat pump, which is an airconditioner that works in reverse. Normally you run an airconditioner to extract heat from your room and dump it outside. Your pool heatpump works by extracting heat from the outside (making it cooler) and dumps heat into your pool (inside).