First Summer as a pool owner - struggling to get up to temperature

[tikigod19]

Hi all. I'm new to the forum and I've heard great things about it!
We moved in Sep 2015 and have a 20x10 6000 galon outdoor pool with a 9kw electric heater. I think it is the 9kw version of this:
In-Line+ Swimming Pool Heater

As we have kids we paid in the winter to have the bubble solar cover replaced by an EZ Cover vinyl thermal lined one. Which I've now read actually stops the solar heat reaching the pool (at least I assume it does as it obviously stops the sun light hitting it)

We turned the heater on at around midday and the temp doesn't seem to be going up. It's sitting on 14 degrees c. Outdoor temperature today was 20 degrees c.

I'm after some general heating advice specific to my situation really. Should I leave the cover closed when heating and in general whenever I can or am i wasting possible heat from the sun?

How long would you expect the pool to take to heat to around 25 degrees c based on an ambient temp of 20-25 degrees c? It currently feels like we're never going to reach close to this temperature and when you're paying £8 per 7 hour stint to heat this is painful!

Please feel free to ask any questions and any advice welcome. I'm sure I'll have many more questions!

David

 

[TexKSAH]

I have a 400,000 BTU gas heater that is the equivalent of roughly a 120kw electrical heater. It takes about 30 minutes to heat my 800 gal hot tub through roughly the same temp range (20-25 deg f or 10-12 deg c). Not accounting for the many variables like ambient temp, heat loss, solar assistance, cover, etc, basic math would suggest it would take 48-50 hours to heat 6000 gals through the same temp range using a 9kw electric heater.

I don't know enough about thermal dymanics and liquid thermal dynamics to verify my calculations, but just based on my experience, it seems it would take a long time to heat your pool with a 9kw electric heater.

By the way, welcome to the forum. This place has helped me tremendously managing my new pool. You will be glad you found it

 

[tikigod19]

Oh my word. 50 hours?!

OK, is this just the initial heat at the start of the summer? Once I'm up to temperature if I keep the cover on when not in use surely it wouldn't drop back down to tap temperature very quickly? Please tell me it wouldn't..

I have a south facing garden with lots of sun.. I'm now thinking solar panels to assist the heater would be a good idea.

 

[tikigod19]

Well, we've gone from 14c to 18c overnight (9 hours) so by those calculations total time to 26c will be 36hrs. (£44...eek)

We are on a flat rate electricity terrific at the moment. The previous owners were on economy 7 paying half price over night when they used to heat the pool.

We are deciding whether to switch back to this but it really depends how long the pool keeps the heat in as it would have taken 4 nights to do this 36hr heat on economy 7 but I wonder how much heat would have been lost even with the cover on between 7am and midnight when the heater was off...

Anyone done similar tests? I'm assuming so! Would love to hear your thoughts

 

[MarianParoo]

Keep the pool open during the day for the sun to heat the water. Close the pool at night to retain the heat.

 

[tikigod19]

That's one thing we were unsure about.. Is that definite for all covers? We have a thick vinyl cover (aquamatic ez cover)

Will the heat lost through evaporation not be greater than the solar heat gained?

I assume we should only leave it open on sunny days too?

Any more info on this greatly apprecoated
. This is a revelation to us..

 

[txnole]

It's difficult for us to know your heat loss with the cover, as they all have different coefficients as environmental factors change. I don't believe your cover stays in contact with the water, so it will not transfer heat from the sun. As such, you should leave the cover off during the daytime. Replace the cover overnight to reduce your temp loss to 1-2c vs. 4-5 (or more!) without cover.

 

[MarianParoo]

As an aside, CC's will accumulate in a covered pool. I try to open mine at least an hour or two everyday to let it breathe. I know you are concerned with temperatures now.

 

[tikigod19]

The cover does touch the water for about 90% of its length, it's only at each end that it lifts up.

Oh yes I'd never consider leaving it uncovered at night!

Well we went in today after 36 hours heating. The temp was 20 degrees c. It was horrible!!

It's now up to 23 (10pm here) and I'm going to leave it overnight. Hopefully it'll be up to 26 tomorrow for our barbecue with 18 friends!

What happens after then once we switch the heater off is anyone's guess.. This is real life trial and error territory! I just hope that after £60 worth of electricity it doesn't drop down significantly in the following few days!