Solar heating question

[kevreh]

Mark-
I have a question about solar pool panels and positioning. But first, my VS pump is going to feed my panels on the second story of my house. I may put them on the other side of the roof peak, which means I’ll add another ~8’ of vertical head in addition to the 16’ just to get to the roof. Based on your Have You Lost Your Head thread this shouldn’t matter much because the resistance of the water going “uphill” is pretty much canceled by the water coming down?

Back to your comment, in my case (since the panels are on the other side of my roof) does it matter if my VRV is on the feed end or the return end, and at the top of the panels?

 

[mas985]

Mark-
I have a question that relates to the above. But first, my VS pump is going to feed my panels on the second story of my house. I may put them on the other side of the roof peak, which means I’ll add another ~8’ of vertical head in addition to the 16’ just to get to the roof. Based on your Have You Lost Your Head thread this shouldn’t matter much because the resistance of the water going “uphill” is pretty much canceled by the water coming down?

Only when the plumbing is completely filled with water will static head be canceled. However, dynamic head will always remain and be dependent on the length, size and shape of the plumbing system. So adding pipe will add some dynamic head but not too much.

Also, you don't want the supply or the return lines to run over the top of the roof as that may create a situation where there are local low spots where water may collect and remain even after draining. Given your location, that could cause freeze damage.

From the highest point of the panels, you want to make sure there is a path for the water that is continuously downwards in elevation for both the supply and return. Eliminate all local high spots where water could remain.

Back to your comment, in my case (since the panels are on the other side of my roof) does it matter if my VRV is on the feed end or the return end, and at the top of the panels?

Normally, the supply side of the panels is lower on the roof than the return side because during priming, air rises and you don't want any air to get trapped in the panels themselves.

As long as you can follow all the above suggestions, the VRV on the supply side should be fine.

 

[kevreh]

Only when the plumbing is completely filled with water will static head be canceled. However, dynamic head will always remain and be dependent on the length, size and shape of the plumbing system. So adding pipe will add some dynamic head but not too much.

Also, you don't want the supply or the return lines to run over the top of the roof as that may create a situation where there are local low spots where water may collect and remain even after draining. Given your location, that could cause freeze damage.

FWIW here's a sat view of my house showing where the panels used to be on the left. Had the roof replaced and had to remove them, and would prefer to put them on the right side, hence up the left side, over the peak, and onto the right side. Reason why is the sunlight is better, and its safer to work on versus the side with a 2 story drop if you fall off the roof installing or maintaining them.

Talking to a tech from the solar panel company he said I could put a ball valve at the bottom of the panels to drain them. Water would just run into the gutter and be taken away from my house. I usually stop using solar well before first frost anyways. Does that address your concern?

From the highest point of the panels, you want to make sure there is a path for the water that is continuously downwards in elevation for both the supply and return. Eliminate all local high spots where water could remain.

Normally, the supply side of the panels is lower on the roof than the return side because during priming, air rises and you don't want any air to get trapped in the panels themselves.

As long as you can follow all the above suggestions, the VRV on the supply side should be fine.

Based on the vortex instructions (https://shop.solardirect.com/pdf/po...s/collectors/vortex/vortex-install-manual.pdf), water would enter from the bottom of the panel, and return from the top and opposite end of the panel array. Which is what your saying I think. When you say "Eliminate all local high spots where water could remain" is that due to the freeze risk?

When you say "VRV on the supply side should be fine." can that be towards the top, or bottom end of panels?

The only issue with my plan of going up and over the roof to the other side is there will always be some water sitting in the panels, which will put pressure on connections.

Appreciate all your feedback.

 

[mas985]

Adding a drain valve would mitigate freeze damage but it means someone needs to go up on the roof and open it. Not something I would want.

The other issue is if water sits in the pipe when the panels are off, it can heat up so hot it will soften the pvc pipe and could deform.

The only consideration for VRV location is the VRV height, the lower it is and the closer to the pump (supply side), the lower the RPM the pump can run.