NG Pool Heater --How long to heat pool?

[CJDahl]

I am considering installation of a Jandy 400,000 BTU NG pool heater to heat my new 25x45 37,000 gallon in-ground pool. I did some rough calcs and came up with about 1 hour to raise pool temperature 1 degree F. Does that sound right? And can one simply extrapolate to get 10 degree increase in 10 hours? Also how much does heat loss to ambient impact time to heat pool? Thanks for any info.

[CarlD]

Not too far off. 1 BTU raises 1 pound of water 1 degree Farenheit. 37000 gallons is, I think, about 335,000 pounds of water--approximately.

There are 7.48 gallons in a cubic foot of water and a cubic foot weighs, I believe, 68 pounds.

A solar cover prevents heat loss.

[KurtV]

I am considering installation of a Jandy 400,000 BTU NG pool heater to heat my new 25x45 37,000 gallon in-ground pool. I did some rough calcs and came up with about 1 hour to raise pool temperature 1 degree F. Does that sound right?
Assuming no heat loss to the surrounding area I calculate about 45 minutes to raise the temperature 1 °F (37000 gallons x 8.34 lbs/gallon divided by 400K BTUs/hour x 60 minutes/hour). So, with the inevitable losses, 1 hour or a bit more sounds reasonable.

And can one simply extrapolate to get 10 degree increase in 10 hours? Also how much does heat loss to ambient impact time to heat pool? Thanks for any info.
The rate of rise will actually increase slightly as the temperature goes up because the value of a BTU (expressed in joules or calories) decreases as water temperature increases. (1059.67 joules at 39 °F vs. 1054.6 joules at 63 °F)

Cheers,
kv

[hzz]

1 degree an hour seems about right.

I have a 350000 btu heater on a 20X40 pool and it raises it about 1 degree an hour so you are definately in the ballpark

[jv4nu]

My pool is only a tad smaller than yours and one degree per hour is just about what it takes. I bought a solar cover last week, mostly to help with the 5-6 degrees I lose at night. It helps tremendously. With gas costs, every little bit helps.