best time to run filter to heat pool

[tigerucla]

We get morning sun, until around 3 pm, but the hottest part of the day here in is around 4-5 pm. If I want to heat the pool (no pool heater), would it be better to run the filter for 8 hours from 8-4 to take advantage of the sunshine, or from 12-8 to take advantage of the warm air temps?

Thanks!

 

[jblizzle]

I don't think it would matter ... the pool water will get the same amount of sun either way. You will only be really getting any heat significant heat addition when the sun is on the pool.

The use of a cover would help prevent heat loss to evaporation when the sun is not on the pool.

BTW: You may not need to be running for 8 hours per day anyway. Might save money with a shorter run time:
pool-school/pump_run_time

 

[tigerucla]

Thanks, Jason

I'm thinking if I run the pump while the surface of the water is being heated (either by sunlight or by ambient temperature), then mixing the water will move the warmed surface water down into the pool and increase the overall water temperature more than if I don't run the pump and the water is not mixing. Another way of thinking of it is that I'm trying to bring the cooler water from the deeper parts of the pool up to the surface to be warmed. But you might be right in that it might not have any significant effect.

As for pump run time, I'm not running it on high the whole time. I'm running for 7 hours on low and 1 hour on high (for the pool sweep). This seems to work pretty well for our pool. And I think our energy usage is pretty low.

 

[jblizzle]

Mixing the water when the sun is on it may better equalize the water temp through the depth, but I do not think it would result in more heat addition to the water.

After I posted about the run time, I realized you have a VS, so figured that was not all on high anyway

 

[tigerucla]

I guess unless someone with a strong physics background chimes in with an answer I don't fully understand, I'll compromise and go from 10-6, running on high from 2-3.

Thanks again, Jason!

 

[jblizzle]

Add some solar panels and my answer will change

 

[tigerucla]

I'm too cheap. But if you're offering... ;-)

 

[jblizzle]

You are in a big enough market, that you may be able to find some used ones on craigslist like I did ... only $50 / panel.

 

[mas985]

The heat gain will probably be about the same but the heat loss could be slightly worse without the pump running because the water temperature at the surface would be slightly higher and thus evaporation would be higher.


However, if you have a cover, then it shouldn't matter much.

 

[ps0303]

The sun is whats going to heat the pool not the fact that it's warm outside. A pool without any direct sun but with warm temps doesn't really get warm at all. You need the direct sun light. Also adding a solar blanket will at least keep the heat in once it gets to your pool water.

If you put a glass of water in direct sun and another one in the shade with the outside temp being 85, the water in direct sun light will heat up.

 

[tigerucla]

Thanks, Paul. That's the kind of answer I was looking for. What do you think about running the pump to circulate the water when the sun's hitting it? Would that help heat the pool faster?

 

[ps0303]

Unless you have an external heat source like solar panels, heat pump, or gas heater you will not heat the pool any faster then mother nature wants you to. Run the pump for 8 to 10 hours a day and keep a solar blanket on it to keep in whatever heat you get from the sun. Certainly running the pump while the sun is directly on will help but you're only going to get so much heat from it.

Here in FL, a pool heated only by the sun, it won't be till probably late May early June before the water is mid to upper 80's. Might not even be till late June depending on how much sun the pool gets. Right now pool temps are running in the upper 70's.

 

[mas985]

If you put a glass of water in direct sun and another one in the shade with the outside temp being 85, the water in direct sun light will heat up.

Actually both will heat up as long as the one in the shade has a lower water temperature than the air and/or environment. The one in the sunlight just heats much faster and to a higher temperature.

There are four basic methods of heat transfer for a pool (both heat gain and heat loss):

Radiation - Sunlight hits the pool and raises the water temperature. A pool also radiates heat back out to the environment for heat loss even during the day.

Evaporation/condensation - Water temperature higher than the dew point will lose heat via evaporation while water temperature lower than the dew point will gain heat with condensation.

Convection - The air above the water can either add heat or remove heat via convection depending on the temperature difference of the water and air.

Conduction - This will occur through the shell of the pool and can again be a net positive or negative depending on the water temperature and ground temperature. For a pool, this is usually a heat loss component.

All four components of heat transfer are always present in a pool. However, evaporation can be significantly reduced with a solar cover and helps with convection and radiation as well.

But as I pointed out earlier, you can reduce the heat loss slightly with circulation during the day when the water can develop a temperature gradient. The heat loss due to evaporation is dependent on water surface temperature so when the pump is not running during the day, the surface water can become warmer than if the pump where running. Therefore the evaporation component of heat loss can be higher without the pump running than with the pump running.