Pool Heating in Winter

[socal]

Hello, I'm looking for info/advice/cost from all of you regarding heating a pool in winter.

First some specs:
Fiberglass pool 10,000 gal
Gas heater 400,000 btu
Southern California desert
Months to heat Nov-Feb [pool is heated by the sun all other months]
Worst scenario ranges during the above months [usually Jan] Air Temp 70ºH/ 45ºL, Water Temp 50º
Desired swim temp 80º
Daily swim/therapy at 3pm

Scenario 1:
Have heater hold a constant ±70º, then bring the temp up to 80º at 3pm [lots of short cycles to hold, one longer cycle to boost the last 10º]

Scenario 2:
Let the temp drop everyday [no heater] to ±50º, then bring the temp up to 80º at 3pm [one massive cycle every day to raise all 30º]
My spa [475 gal] heats at about 1º per minute, so using that as a rough guide 10,000 gal would take 10.5 hrs to raise 30º

The Gas Company estimated ±20 Therms/day heating 5 hrs x 30 days = ±$600 month [ouch!!] at 10 hrs we are looking more at $1200 [double ouch!!]

Not looking for solar or pool cover info.

Look forward to hearing from you all

 

[X-PertPool]

That estimate seems pretty close if you don't have a solar cover on the pool. I've had customers tell me they spend more heating there pool than there house ( of course they don't use a solar cover though)

 

[chiefwej]

Without a solar cover you are fighting a losing battle. You will heat the pool each day and lose all the heat each night. With a cover you can retain most of the heat overnight. We are now running night time temps in the 50's and I have a solar heating system. My pool is now at 85, while my neighbor's which is very similar also with a solar system, is in the low 70's. The only difference is that I keep a cover on the pool at night.

The cost of making up for the night time heat loss will make heating a pool for year-round use a very, very expensive proposition unless you keep it covered.

 

[socal]

Guys, I asked for NO INFO ON SOLAR OR COVERS, these are not options!!

Could some people please post pros/cons of scenarios 1 & 2

Thanks

 

[carlscan26]

There have been other threads and if I recall correctly maintaining a core constant temperature vs. swinging back and forth is usually more efficient. So your scenario 1 option *should probably* be cheaper.

:blah: You may not want to hear this but both the other posters are still correct - it will cost you more without a cover You made it clear with your second post that this is not an option but can you blame us for trying to give you the best and most thorough advice?

 

[bk406]

If it were me, id do senerio #1.

I understand you not wanting solar heat. But, i cant figure out why you wont consider using a solar cover along with your gas heat. Man, without a solar cover, you are going to burn through gas like no tomorrow! Use of a solar cover will cut you gas bill by at least a third.

 

[carlscan26]

If it were me, id do senerio #1.

I understand you not wanting solar heat. But, i cant figure out why you wont consider using a solar cover along with your gas heat. Man, without a solar cover, you are going to burn through gas like no tomorrow! Use of a solar cover will cut you gas bill by at least a third.

BK - are you poking the beast?

 

[X-PertPool]

I'd go with Scenario 1:

Just make sure to use a solar cover

 

[XsAllOverIt]

I can only go on my hot tub which is 600 gallons during the winter. I ran my hot tub all winter and kept it at 70 degrees unless we used it, BUT we did have a cover on the hot tub which SAVES MUCH $$$. My average cost per month was about $60. The temperatures were in the 30's normally and one month in the teens. The month in the teens cost us about $120. I think running your heater from 50 to 80 from 3:00 pm on, you'll never get your temperature up to your desired temperature as you indicate, so how can that be an option? Going from 70 to 80 will also take quite some time for a 10000 gallon pool. Raising my 22000 gallon pool from 65 to 80 took a full day the last time I tried it and I didn't use a solar cover when doing it. Only tried it once after getting the gas bill.

 

[ping]

Either way of running, your heater still needs to raise the temp up to 80 from the temp you started at. Do you know for sure you are going to be dropping 30 degrees every night by not running the heater at night? I suggest trying both ways and see which one is cheaper.

Not only do you have the gas bill to pay, you also will have the electric bill to pay. The longer your pump runs, you also have to figure your electric bill. It will not be cheap any way you try it.

 

[Pool Clown]

+1 option 1.

Only keep the pool temp where you want it constantly. You will have to adjust your run time(s) accordingly to keep the temp stable overnite. Maintaining one temp is the best way to go.

 

[daddybug]

Have you looked into liquid solar cover, it might help with your overnight temp loss.

 

[adelman]

Sorry to open an old thread, but...

Once you initially heat the pool to 80F, the heater needs to run only to replace the heat energy which is lost, through the air, through the soil, radiated, or through evaporation. Specifically, the energy the heater needs to produce is equal to the energy lost through these mechanism. All of these mechanisms for heat energy loss are a function of the heat gradient (difference between the pool temperature and the ambient temperature). The higher the gradient, the higher the loss.

All other things being the same (i.e., not adding a cover), less energy is lost when the pool is colder. You want a heating schedule that results in the lowest average temperature throughout each day. The most energy efficient way to meet that schedule is to start the heater such that it will run continuously until you want the pool warmed, and hit the 80F temperature right as you get into the water. Then shut the heater off and let the pool cool.