Solar panels on east and west sides of roof. Design advice

[mas985]

The check valve is a swing valve, not a spring valve and I installed it for the solar. Do some swing valves have a lot of head loss?

They shouldn't so it must be something else.

Isaac's idea of the siphon effect make sense but hydraulics aren't even in the realm of my specialties. Maybe I need to divert some water directly to the return instead of 100% to the solar. I think I tried that last summer but I can't remember for sure.

That would make things worse not better. You want higher pressure at the VRV and bypassing only lowers the pressure.

Maybe you should try removing the VRV and using a plug to get a good seal. The other possibility is that at the top of the panels, there is a small leak and that is sucking in air.

This also plays into the question of getting a pump with a higher curve. I am less concerned with electric costs and more with warming the pool which keeps my wife happy.

If it were me, I would try to figure out what is wrong with the current setup. A higher head pump may or may not fix the problem so there is some risk there.

Just an FYI, I have a 1/2 HP pump with a head curve similar to yours and that runs solar on a two story roof.

 

[Isaac-1]

It map be helpful to temporarily remove the the VRV and install a low pressure gauge in its place to see if you are getting positive or negative pressure at that location when the solar is running.

You might also want to try to partly close the red return from solar valve to add more restriction on the return path to confirm the problem is the siphon effect of that large water column.

 

[rhaas12321]

The other possibility is that at the top of the panels, there is a small leak and that is sucking in air.

You had to say the "L" word, didn't you!
I don't want to admit it (to myself) but there probably is. Wouldn't I see water coming out rather than air sucking in?

Maybe you should try removing the VRV and using a plug to get a good seal.

It may be helpful to temporarily remove the the VRV and install a low pressure gauge in its place to see if you are getting positive or negative pressure at that location when the solar is running.

You might also want to try to partly close the red return from solar valve to add more restriction on the return path to confirm the problem is the siphon effect of that large water column.

I will try these when I open the pool, probably late April. Maybe I'll open early to get a run at it, it's only a couple extra gallons of bleach



I really wanted to open with the new pump, the MaxFlo came with the house so it is probably 10 years old and has leaked since day 1, even with the rebuilds.

If I read Pump Tools correctly:
MaxFLo approx. 45 gpm
WFE-3 approx. 55 gpm
WFE-4 approx. 70 gpm

So I am still gaining ground with the WFE-3 and probably shouldn't get the WFE-4. It just, for $40 more, it's hard not to say More is Better.

 

[mas985]

Wouldn't I see water coming out rather than air sucking in?

Depends on the pressure at the point of the leak. The rise in the panels (assuming 15' rise) loses about 6.5 PSI of pressure. If the filter pressure is 18 PSI and there is more than 11.5 PSI of head loss between the filter gauge and the leak, then the pressure at the leak will be below atmospheric pressure and air will leak into the plumbing at that point. You just need to find out where that leak may be.



Also, if you are going with a new pump, why not get a two speed pump while you are at it?


Also, on standard 2" plumbing, the MaxFlo should be delivering about 64 GPM but because of excess head loss, it is much less than that.

Again, No matter if you go with a new pump or not, I would find out what is causing so much head loss in your plumbing.

 

[rhaas12321]

Depends on the pressure at the point of the leak. The rise in the panels (assuming 15' rise) loses about 6.5 PSI of pressure. If the filter pressure is 18 PSI and there is more than 11.5 PSI of head loss between the filter gauge and the leak, then the pressure at the leak will be below atmospheric pressure and air will leak into the plumbing at that point. You just need to find out where that leak may be.

The minor leak I have is in a small tube right at the very top of the panels, about 25' up (it's a steep pitch roof). Does that mean there is positive pressure through out the solar system or could it still be sucking in air somewhere else?

Also, if you are going with a new pump, why not get a two speed pump while you are at it?
Also, on standard 2" plumbing, the MaxFlo should be delivering about 64 GPM but because of excess head loss, it is much less than that.

The solar was on 100% of the time (late) last season and since I didn't think the solar would work on low speed, I though I would only need high speed. Electric is about 0.10 / kwh.

I calculated the flow using my very basic understanding of pump tools. I have 2" plumbing on the new solar setup but only 1.5" on the existing pool.

Again, No matter if you go with a new pump or not, I would find out what is causing so much head loss in your plumbing.

At this point I guess my best option is open this season with the old pump and figure out the problem. I'll get a pressure gauge and put it in place of the VRV and see what it shows.

Can you translate pressure drop into head loss, i.e. a reading of 8 psi = xx feet of head loss? Maybe I don't need to calculate the head loss but I do like understanding the situation so I can make more informed decisions.