Trying to keep up w/ Chem Geek

[chem geek]

ShellyAnn,

It is not true that simply increasing the rate of flow through the solar panels increases the amount of heating to your pool. There is a point of diminishing returns. Though every manufacturer's solar panel is different, take a look at this link which is a common solar panel from FAFCO and look at the graph that says "EFFICIENCY vs. FLOW". You will notice that you get to 80% efficiency at a rate through the panel of 4 GPM, but that the efficiency increase is slowing way down. The maximum flow rate recommended for this panel is 8 GPM, but the efficiency won't be very much higher (it won't be more than 90%).

When water flows faster through your panel, it spends less time in the panel so gets heated up less. So while you push more water through the panel at higher flow rates, it gets heated up less and the net result is roughly the same amount of temperature rise in your pool. You should generally stay near the recommended flow rate for your panel and not exceed its maximum rate.

I don't know enough about your system to know if you need a 1.5 HP pump, but that seems extraordinarily high. I have exceptionally long runs for my solar setup (due to many roof segments and hips) and am already over-pumped at 1.0 HP and could easily use 0.75 HP. It is true that sand and DE filters have higher pressure (at the same flow rate) compared to cartridge filters, but even so the pump seems over-specified. Your pool builder is recommending a 21" high rate sand filter and yet your pool is an above-ground 15x30 which is not a very large pool (it's not small, but it's not so big as to require "high-rate" and a large pump for fast turnover). This just doesn't seem right to me.

At any rate, you most certainly want to have a bypass for your solar panels so that only some of the water goes through them since there is no way you can run high rates like 50 GPM through just 3 panels (for 17 GPM each) unless your panels are of a design very different than the FAFCO one in the link above. The setups that Al and Carl described in previous posts sound good where you can split the output of your pump to go partly through the solar panels and the rest into your pool. My only concern is that your PB is designing a high flow-rate system, including a filter designed for such flow rates, without good reason (except more expense for a larger pump and high-flow rate filter). Even if your pool were 4 feet deep throughout, that would be about 13,500 gallons so to get one turnover in even 4 hours (so two in 8 hours) would be 56 GPM, but it sounds like your PB is designing your system for even higher flow rates. Maybe when he is quoting 1.5 HP he is talking about an "up-rated" pump so that this is roughly equivalent to a 1.0 HP "full-rated" pump. That would make more sense.

Richard