Solar Roof Heater Care & Maintenance

[Frenchie250F]

Does anyone have any experience or background with proper care and maintenance of solar roof heating panels?

The panels on my roof (~160 sqft of them, likely oversized for the pool I have, black plastic mat type) were installed by the previous owner I'm guessing ~10-12 years ago. Based on general life estimates and the look of them, it seems they have a 2-3 good years left in them. My roof probably has ~5-6 years left in it. I'm hoping get a few extra years out of the "standard" 15 years for roof solar plastic so I can replace them at the same time.

My main question is, does anyone else think its crazy to leave them run dry on hot summer days? I've been doing some searching online, and can't seem to find any solid opinions on this, but I feel like NOT running water through them during the hottest part of the day is just asking for damage on the plastic. Problem is, if I keep pumping water through, my pool temperature is way above bath water temperature. A few people I know say they leave them off during the day, but I haven't gotten a solid response if this does or doesn't hurt the lifetime.

Any other tips or tricks for keeping them in good shape would be appreciated.

 

[JohnT]

You can definitely leave them empty during the day. The one thing you don't want to do is to leave them full of water that isn't moving, so just make sure they are drained and you can safely operate with the panels bypassed.

 

[CJadamec]

Just curious what difference does it make if there is water in the panel or not? With no water flowing through them they will get to the same temperature with or without water in them. Unless you have both the supply and return lines valved out there should always be a path for any extra pressure generated from the heat in the panels to make its way back the return line to the pool.
Is it simply the weight of the water on the hot plastic you are concerned about?

 

[domct203]

If that water should start to boil and create steam, your panels will be damaged from the trapped pressures.

 

[CJadamec]

The solar panel isn't a closed system there is always an open path to release pressure back to the pool through the return line. At worst you will have about 2 psi generated to open a check valve.

 

[domct203]

Good point. Then why must we drain the panels?

 

[JohnT]

It's not pressure, but the weight of the water in the plumbing creating suction on hot panels that can deform them.

 

[CJadamec]

The VRV prevents negative pressure no?

 

[JohnT]

The VRV prevents negative pressure no?

It's supposed to, and it should let the panels drain when the valve is set to bypass them. But if the panels have water in them while not flowing, something isn't working or isn't configured right and you are going to have negative pressure.

 

[Frenchie250F]

It's less a concern about pressure/steam/stagnant water, and more just straight temperature.

As far as I can tell, the VRV is working correctly. Once bypassed (or if the pump is turned off) the panels drain (correspondingly, after turning them back on it refills them and pumps air back through the system for ~30 seconds, which scared the daylights out of me during my first few days of pool ownership...). So no, I don't think there's a concern about pressure (both positive or negative).

My concern was more, without water in the system, the plastic gets very very hot to the touch (its black plastic sitting in the sun, probably hotter than the shingles). With water flowing through it, its definitely warm, but never burning to the touch, since the water will always act as a heat sink, even if the pool starts getting up in the 95 degree range. If any car's dashboard is proof, plastic baking in the sun is never a good thing, be it from heat, or UV light damage. But if everyone seems to do it, maybe its less heat related and more UV.