Solar panels

[cape coral dan1]

Just bought a home with a pool. My first pool. The pool system has 8 each, 4' X 10' solar panels on the house roof. The valving on the output of the water filter is set-up to send 1/2 the water filter output to the solar panels which returns to the in-line chlorinator ... and the other 1/2 of the water filter output directly to the same in-line chlorinator. In this mode the PSI gauge on top of the water filter reads 10 PSI, and has always been 10 PSI in this mode of operation since we arrived 3 months ago.

If I change the valve on the output of the water filter to send 100% of its water to (only) the solar panels, which then returns to the chlorinator, the PSI gauge on top of the water filter will change to 25 PSI (the water filter max allowable pressure is 50 PSI). The pool system piping is 2" PVC with the exception of the feed and return PVC pipes that go up to and inter-connect the solar panels ... they are 1-1/2". I have a brand new 100 Sq. Ft. filter element in the water filter.

Is the 15 PSI increase in "back pressure" due solely to the solar panel's reduced pipe size, the addition of the solar panels resistance, and the further distance the water must travel to get to the pool? Is this normal? Will I reduce the life of the water pump? Need some words of wisdom from the experts.

Note: I have lots of other questions but I'll start with this one. Regards.

[mas985]

What you are seeing is normal and no it won't shorten the life of the pump. In fact, pumps draw less current and use less power when the pressure is higher (i.e. lower flow rates). When you redirect more water through the solar panels the head loss in those panels increases and the pump flow rate will decrease. Head loss in plumbing is proportional to the flow rate squared.

But 10 PSI may not be enough pressure to keep the VRV (vacuum release valve) closed so you may need to redirect more water to the panels. How high are the panels and where is the VRV installed?

[cape coral dan]

Thanks for the reply mas985. Didn't even know I had a VRV ... I will have to look around and see if I can find it. The only valve I'm aware of is the pressure relief valve on top of my water filter that I use to bleed off air sometimes.

My 8 each, solar panels (320 Sq Ft) are mounted on my home's roof. 4 are on the lower portion of the roof and 4 more are mounted above them on a higher portion of the same roof. The bottom of the lower panels is 9' above the water pump output line and the top of the lower panels is 14'. The bottom of the upper panels is 14' above the water pump output line and the top is 19'. 100% of the water pump output is going to the solar panels.

Yesterday was a bright and sunny day with a high of 85*. The pump turned on at 10 AM and the pool water temperature was 80* at that time. 100% of the water pump output was going to the solar panels that have a southern exposure. By 5 PM, when the pump shut off, the pool water temperature was 85*. At 10 AM this morning, before the water pump turned on again, the pool water temperature was 80* and the ambient temperature was 72*. Last night's low was 67*. I do not use a thermal blanket on the pool.

[mas985]

Typically a VRV is installed at the upper most point of the panels.

Assuming it is at the highest point, 19', the CLEAN filter pressure required to keep it closed will need to be at least 8 PSI and probably a few PSI higher depending on the head loss between the filter gauge and the VRV so 10 PSI might be the correct level although it doesn't allow for the PSI rise of a dirty filter. Should you start to see air bubbles in the pool returns, this could be a sign that the VRV pressure is too low and you may need to redirect more flow to the panels.

[cape coral dan]

Interesting. When the pump is off I always hear "gurgling" noises around the water filter an associated piping. This goes on for hours. I always though it was water draining back/down from the solar panels and maybe a check valve somewhere was leaking. Upon starting the water pump the next day, with the solar panels getting 100% of the water flow, I get lots of "air" out of the "returned water" pool jets. This major air discharge will go on for 2 or 3 minutes and then slowly decrease in volume during the next couple of minutes. The water jets closest to the water pump discharge the most air. An hour later I will still get a very small stream of high velocity bubbles.

So does this mean the VRV is draining the panels when the pump is off ... by design ?? Does it also mean that with the water pump running, if I do not have sufficient pressure in the solar panels the VRV will open and allow pool water to escape ... to run down the roof to the roof gutters and then to the ground ?? Haven't seen any strange water flow from the gutters or water drainage on the roof.

Regards, Dan

[mas985]

Again, this is normal. The VRV is there to allow the panels to drain when the pump is off. When the pump is on, the pump needs to re-prime the panels and a push all that air out of the panels and through the returns. However, at some point this air should stop when the panels are fully primed. If the air continues for more than about 5 min, then there might be a problem with the VRV not closing.

But if the VRV does not close, it does not mean water comes out, usually, it means air goes in. If there was enough pressure to force water out of the VRV, the VRV would close and everything would be fine. But when the pressure is too low after the filter, the pressure at the VRV can be lower than atmospheric and then air is drawn into the plumbing causing continuous bubbles out of the returns.

[cape coral dan]

..... again Mark, thanks for taking the time to educate me. I can see I have some homework to do regarding "Head" and "Pool Plumbing". I saw the "Link" in your "Signature space" and will start there.

Regards, Dan