Vacuum relief- solar panels??

[uncledeadly]

I do not have a vacuum relief on my solar panels but have now decided that I should have one .
I phoned my friendly neighbourhood pool store to see if they carried these. " No we don't install solar panels so we don't carry the components"
Do you k now who does install solar panels around here?.... No.
Thanks for all your help.

I phoned a plumbing supply house and asked if they had a 3/4" vacuum relief . They do not but they do have a 1/2" in stock.
Has anybody used a 1/2" relief valve or can anybody see why it should not work?

 

[Bama Rambler]

A 1/2" should work fine. You can install a check valve with the flow toward the solar panel and it works just as well. It'll allow air in but not water out.

 

[mas985]

1/2" or 3/4" should work fine. They simply allow air to enter the plumbing when the pump is shut off. The 1/2" will take a bit longer but should be fine and not really affect anything.

I assume that the panels are installed on the roof?

 

[uncledeadly]

Yes, the solar panels are on the roof. I have 9- 4x10 panels and just installed a tap on the top and bottom corner so that when I went to winterizing I can just manually open the taps and allow air in the top and the water to drain out the bottom. I didn't give any though to the suction that was created when the 3 way shuts off and after reading info on this site and other info as to the damage that could be done (ie. panel capillaries collapsing under the suction) decided to install a couple of check valves and a vacuum relief. I've read that the panels will last alot longer if they are evacuated of water when not in use. Correct?

 

[mas985]

The panels may or may not last longer with a vacuum release but it stands to reason that they would. As for collapsing, I have heard of cases in very hot areas such as Arizona and central California where the water sat in the panels during the day heating up and when the pump was shut off, the PVC return pipe collapsed under the high heat and high vacuum. Usually the panels themselves can withstand the high vacuum either because they are flexible, as in EPDM, or polypropylene which doesn't soften much with heat. However standard PVC can get quite soft with high heat so it doesn't take much to deform or collapse the pipe. A vaccum release valve at the top of the panels will help avoid such problems but mounted in a lower position can still have that problem. An installer once told me that when they started to install vacuum release valves about 6 ft above the pad for easier access, they started to see more incidences of collapsed PVC.