Vacuum release not closing

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Generally, you want about 0.1 GPM/sq-ft of panels. That's where the 4-5 GPM comes from because those panels tend to be 4x10 or 4x12. But not all panels are that size.

But why would you want to divert the flow? I would say set the flow for the panel efficiency and leave it at that. That's the whole point of having a VS.
 
So panel area is 41.67ftsq X 3 panels = 125ftsq X 0.1gpm X 12.5gpm . I set the VF for 20gpm for solar this morning and it ran ok for 15mins no bubbles , then the VF gave a system blocked message then restarted . It has been running at 25gpm for an hour now no problems .

I wonder if the check valve on the solar side of the system is causing head loss ? , it is a jandy hi flow one but ? . I don't see much purpose to it as the three way valve shuts when solar turns off and stops any water returning to the filter within 15 seconds plus the pump is still running .

The filter is clean and shows 15kpa or 2.1psi . maybe gpm needs to be higher at the pumps to account for all the pumping but I thought restrictions just cause a rise in pressure to maintain flow ? that why I see high filter pressure when running solar ?

I might try setting to 13gpm and see what happens .
 
Sticky said:
I wonder if the check valve on the solar side of the system is causing head loss ? , it is a jandy hi flow one but ? . I don't see much purpose to it as the three way valve shuts when solar turns off and stops any water returning to the filter within 15 seconds plus the pump is still running .
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Yes, the check valve causes head loss and yes it gets worse at lower flow rates. Removing the spring will help but save it in case you want to put it back on. You can push the pin out of the flapper to remove it.

The check valved is necessary because even though the solar valve shuts off the supply side of the panels, it does not shut off the return side so when the pump shuts off, the return side can still drain backwards through the filter. Also, if the solar valve has a hole, which most do, the supply side will still drain out of the valve and could go backwards through the filter.

What is the pump RPM when it is set for 20 GPM?
 
well I took out the spring ran at 25gpm 1205watts , I then set the Ext control to 20gpm when the solar turns on the VF gives a system blocked ! alarm then primes then settles to 950-960rpm 160watts it will run like this for 5mins then give the system blocked ! alarm , the manual says this will happen with a supply/suction blockage or a few seconds of dead heading .

I thought the VF would just increase the rpm to provide pressure for the flow , it seems when the flow gpm is set to low the pump has trouble . I going to try running all 3 returns at 20gpm .
 
Ok if i run with all three returns open the pump runs at 20gpm 895rpm but the there is nothing coming out of the deep return , when I try to ajust the flow to give more to the deep return the system shut down . it seem the problem is on the return side .
 
after some reading Marks Hydraulics 101 and pumped 101 I think this is whats going on .

As this speed rpm of the pumps impeller slows the head produced by the pump is reduced , this from pumped101 " Head varies as the square of a change in rotational speed or impeller diameter (peripheral velocity). Double the speed or diameter and head increases by four " so once rpms settle to 950rpm the head is to low , The static head loss on the way up is no longer offset by the static head gain on the way down because by using just the one deep return there is an imbalance ? that the lower head cannot over come .

With two shallow returns used there is less back pressure ? which allows it to run at 20gpm and 895rpm , it may even run lower have not try it yet . But I lose flow to the deep return where the colder water would be displaced .
 

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If the RPM is dropped too low, pressure will drop opening the VRV and losing panel prime which will dramatically increase the pump head creating a dead head condition for low RPM conditions. This can be offset some but increasing the pressure downstream (smaller eyeballs) from the VRV but there is only so much you can do.

This is what I would do. I would force all of the water to go through the panels. Gradually reduce RPM until you get an alarm condition. Then raise it back up to the previous setting and leave it there. At that point if the flow rate is more than you need for the panels, you can bypass some of it. However, this will lower the pressure at the VRV and could cause the VRV to leak some so you may need to up the RPM again. You might be better off just leaving the bypass closed.
 
Hi Mark ,

The VRV problem seems solved by moving it closer to the pump , its on the wall leading to the roof and just using the one deep return increasing the pressure downstream .

The problem is that the VF External control feature only lets you set gpm not rpm so the only way is to keep rpm up is to up gpm .

Another option is just to add two more panels , this would bring the total required flow up to 20gpm close enough to the 25gpm I run now ok . also would heat the pool faster .
 
So have you moved the VRV or not yet?

Also, the flow rate can be much higher than 0.1 GPM/sq-ft. There is no real problem with that given the pressure is so low anyway. So 25 GPM should not be an issue really. Plus once the pump RPM drops below 800 RPM, the energy efficiency starts to drop too.
 
Yes I have moved the VRV plus increasing the downstream pressure by just using the deep return .

I think I just have to be happy with 25gpm and your there obviously is not that much pressure at the lower rpm range and that's what you need to avoid is over a pressurized solar system .

Thanks for your help

Dave
 
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