Domestic pool turnover rates

[CarlD]

Richard,
I've read your posts with interest (as I almost always do). I'm baffled by one thing: Why do your solar panels require so much pressure? While I've long been an advocated of "More Flow = More Heat Energy", it seems awfully high and from what I've seen of solar panels, they are prone to leaking when the pressure is too high--I run mine on low speed all the time. When I bump the pump to high, I either turn off the panels, or shut their valves down to a crack, a trickle, to prevent them leaking. Of course FantaSea panels, nifty as they are, are far more fragile than the flexible roll-up types. I'm always checking for and repairing leaks.

As for the lower TA: I'm pretty sure it wasn't Ben who first put the concept forward. I thought it was one of the pool pros--or you--who suggested it (guess it wasn't you). Of course, in practice many of us have found it to be VERY effective to countering rising pH. Rising pH seems more mysterious than falling pH, which is almost always easy to trace, usually to Tri-Chlor or even Di-Chlor. Only with new or newly resurfaced hard (concrete/plaster) sided pools is rising pH expected.

But rising pH can be, as you know, an adverse effect of an SWCG. Many people complain about it. Yet I don't seem to have that problem and haven't in the 3 seasons I've had the SWCG. In fact, my pH has been pretty constant since I re-opened (and the Tri-Chlor tabs ran out) at 7.5-7.6 Yet my TA is around 170 due to the local water. Since pH IS stable, it ain't broke, so I'm not fixin' it!

[mas985]

Not to answer for CG but for solar panels on a roof with a VRV installed on the roof, you must have positive pressure at the VRV to keep it closed. Pressure drops with elevation so on a two story roof, you must have at least 11-15 PSI on the filter in order for the VRV to remain closed. A one story is better at 5-7 PSI filter pressure.

Carl, if I remember correctly, I believe your panels are in your deck so you can easily run on low speed to run the panels.

Lowering of the VRV would also allow someone to run at low speed on a two story roof but you still need to prime the panels on high speed so the controller must support that.

[CarlD]

Thanks, Mark. Yes, it's correct that my solar panels are part of my deck and priming them is only an issue in the spring because they were drained for the winter. Other panels I've used have also not been elevated so I've no experience with the control valves needed.

[chem geek]

The recommended flow rate for my solar panels is 4 GPM per panel and I have 12 panels in parallel so that's 48 GPM. I could run slower with somewhat less efficiency. Even going from 4 GPM per panel to 3 GPM per panel (which is the "minimum recommended") only drops efficiency from 80% to 70% while energy usage would drop from 1500 Watts down to less than 900 Watts. Or I could split the difference and do 3.5 GPM per panel at less than 1200 Watts. I've considered doing that, but haven't changed to it yet. My wife often swims earlier in the day so needs the heating to occur more quickly, but it's a dance for how high to get the temperature the night before so that it is warm enough at the start of the next day.

The other reason my pump energy cost is pretty high when solar is running is that I have a long 75 foot pipe run to and then from the solar system on the single-story roof. I lose 1.2 PSI because my PB used 2" pipe instead of 2.5" (or 3") plus the 12 panels are spread over 3 different roof hips over the length of the house. Also, marginal electricity rates are high at 35 cents per kilowatt-hour (or more). My filter pressure with solar at 48 GPM is roughly 24 PSI which is high (55 feet of head) where the highest point of solar on the roof is perhaps 20 feet high so the rest is largely inefficiency in the piping and outlets. I'm sure I could operate at a slower flow rate without the VRV opening since 36 GPM with solar on is roughly 16 PSI in my pool system.

[CarlD]

Thanks for the explanation, Richard.
Do you use a solar cover at night, too, to hold in heat? I find it's critical to efficiency.
If you have an attic, have you thought of running additional plumbing through THAT to pick up more heat energy?

Luckily, since my panels are only about 3 1/2' above my pump and, at most 10' away, I don't have to deal with all those issues you do.

[chem geek]

I have an automatic electric safety cover that is on all the time except when the pool is in use. The pool is used almost every day for about an hour or two. And yes, having a solar system without a pool cover will have less benefit. Basically, with no cover then overnight in the non-peak of the swim season I can lose 6ºF but with the thin non-insulating but opaque cover I lose 3ºF. If I had an insulating bubble-type cover, I'd lose around 1.5ºF.

The solar panels on the roof pick up the sun's energy directly so our attic is cool when they are running and is a side benefit to keeping the house cooler as well (though the attic is fairly well insulated from the house interior). It's more efficient to have the panels on the roof than it would be having them in the attic. For maximum efficiency in the attic one would want very dark roof tiles thermally connected to the attic. The fact that our synthetic shingles are gray and not black has them not absorb as much heat as the black solar panels and they do not transfer the heat as efficiently to the attic through the roofing materials. Roof attic heating is not an efficient solution unless the roof was designed specifically for that purpose -- it's not that such systems don't work, but that they aren't as efficient as panels on the roof.

[CarlD]

Hm.....Can you find a way to velcro a solar cover to the underside of the auto safety cover?