Possible solar plumbing problem?

[Bama Rambler]

If the two 90's are back to back or close to it they could raise the pressure some. When you put the filter back together you made sure eveything lined up correctly didn't you? 16 psi should be ok to ruun with. I'm still puzzled as to why it didn't go back to original when you changed the DE.

After looking at the plumbing again. Did you change anything on the pump suction? there is what looks like new piping there. Just a thought but if the suction is less restricted than it was, the pressure could be up just because of that.

 

[robrinker]

The two 90's are about 4 inches apart, so hopefully that explains it.

As for the suction side, I assume you are referring to the two white ball valves that are on the skimmer lines underneath the new solar lines. I replaced those last year because the handles were broken on the old valves when we bought the house, so they shouldn't figure into the equation.

I just finished gluing in the new union to connect the pipe I cut to do the testing. It looks like it might be sunny here tomorrow, so hopefully I will see if we've made any improvements to the panels.

 

[mas985]

In order for two 1.5" 90s to cause a 4 PSI rise, the flow rate would need to be 150 GPM.

For a typical flow rate of 65 GPM for your size pump, the pressure rise would only be about 0.75 PSI. Something else in addition to the 90s is causing the increase in pressure. Even if I include two tees and the valve, I still only get about 2 PSI. What other fittings did you add?

 

[robrinker]

OK. We are approaching normalcy. I tested the plumbing this morning and filter pressure is at 14psi with solar off. This seems to agree with your calculation Mark. Perhaps the backwash hose I was using to connect the filter directly to the return line was only 1 1/4" or 1" ID? Would that account for the extra 2psi?

Now, when I divert all of the flow to solar, filter pressure increases to 20psi.

Which leaves me with one final question: do I want to send everything to the panels, or should I only close the solar valve until I get a 2psi increase, or do I base this on the surface temperature of the panels when they are in full sun? (ie, only send them enough pressure till they stay cool to the touch.)

 

[Bama Rambler]

If it were me, I would send everything to the panels and then balance the individual panels based on delta temp between the panels. The more flow through the panels, the more heating you're going to get and that's what you're after. Flow would be a better way to balance them but I'm sure you don't want to install 3 or 4 flow meters. Besides for what you're wanting temp will work just fine.

 

[mas985]

It probably won't hurt anything to send all of the water through the panels since the max pressure is only 20 PSI. The only downside is a longer turnover and thus longer pump run times since the flow rate decreases with iincreasing pressure. The panels will reach a maximum efficiency after which there isn't much improvement so you can probably safely back off. Usually, those panels will max out at about 4 GPM per strip and since you have 12, that is about 48 GPM. Assuming I counted correctly. One thing you could try is to set the valve such that the pressure rise is about 1/2 or 3/4 of maximum. Then check the panel temperature and see if they are at the same at full flow vs reduced.