Sizing Solar and pump efficiency

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Oh ok, we have seen some members where they NEVER opened up the filter and it was practically solid with DE and dirt.

Although, this still could be part of the problem. How often do you backwash? you filter takes 6 pounds after a full break down. When just backwashing not all of the DE is removed so we suggest only adding 80% of the full load which would be just under 5 pounds after a backwash.

Now that it is spring, certainly would not hurt to break it down again and eliminate that as the source of blockage.
 
fengshui said:
I did further testing this morning. With both the heater and solar bypassed and confirmed, I was able to get to 55 GPM flow, 3450 RPM, and about 2200 kW on the system. Pressure on the filter was 32 PSI.
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This seems inconsistent with your previous posts. If you bypass equipment on the return side, you should get lower PSI, not higher PSI. What was the configuration where you said you got 20 PSI? The filter and solar are plumbed after the filter, correct?
 
jblizzle said:
Oh ok, we have seen some members where they NEVER opened up the filter and it was practically solid with DE and dirt.

Although, this still could be part of the problem. How often do you backwash? you filter takes 6 pounds after a full break down. When just backwashing not all of the DE is removed so we suggest only adding 80% of the full load which would be just under 5 pounds after a backwash.

Now that it is spring, certainly would not hurt to break it down again and eliminate that as the source of blockage.
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Agreed. It's nearly time for the annual clean-out. I'll try to make that happen this weekend. Thinking about it, I could even test the system with the filters completely removed to see if that was the factor.

This seems inconsistent with your previous posts. If you bypass equipment on the return side, you should get lower PSI, not higher PSI. What was the configuration where you said you got 20 PSI? The filter and solar are plumbed after the filter, correct?
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The 20PSI number was what it normally runs at, and at about 40GPM. Currently, I could use a backwash/filter cleanout, and I'm running at near 55GPM.

To circle around to my original question, given what we know about the system now, would you recommend extending the solar system from 8 panels to 10? I was hesitant to do that with my limited flow available. If I get this resolved, would 40GPM (the flow I need for 10 panels) be something I could reach at under 1500 Watts? Under 1000 Watts?
 
fengshui said:
The 20PSI number was what it normally runs at, and at about 40GPM. Currently, I could use a backwash/filter cleanout, and I'm running at near 55GPM.
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That makes no sense to me. As the filter gets dirty, yes the pressure goes up but that means the flow rate goes down, not up.

I think we need to resolve these issue before deciding on next steps. Filter pressure is very important when troubleshooting a system. So can you tell what the filter pressure is with solar on vs off without changing anything else?
 
mas985 said:
That makes no sense to me. As the filter gets dirty, yes the pressure goes up but that means the flow rate goes down, not up.

I think we need to resolve these issue before deciding on next steps. Filter pressure is very important when troubleshooting a system. So can you tell what the filter pressure is with solar on vs off without changing anything else?
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I wasn't clear. Certainly as the filter gets dirtier, the pressure goes up. I've gone from 20 to 30 as the filter gets dirtier. However, since I have an Intelliflo VF, the pump will increase speed to maintain a particular flow. The change from 40 to 50 is probably more due to the removal of the crawler and the bypass of the solar.

I'll post updated data after the filter is cleaned out, and we'll see how high I can get the flow. From what you've described, I should be able to get to near 100GPM without too much trouble, correct?
 
I gathered a lot of data this weekend. The full data is below, but my conclusion was that the DE filter was overloaded and clogged. Thinking back, I probably was putting in too much DE on re-fill, and not correcting for the DE left in the filter after backwash. I was able to hit 85GPM in all modes I tested (empty filter, filters only, filters + DE). With the suction crawler installed, I was able to get 40 GPM at 2070 RPM, 616 W, and 3 PSI. 60 GPM was unattainable with the suction crawler.

The issue now is the solar. With the system running at 32GPM, (1790 RPM, 420 W, 2 PSI) turning on the solar jumped RPM to 2340, Power to 750W and PSI to 10. Is that a reasonable jump for a solar system? The specs I can find for FAFCO solar panels list an expected head loss of 0.87psi for a single panel. I have 8 panels in parallel. I would think that would still leave me at around 1 PSI of head loss for the panels. However, I saw a jump of 8 PSI. Is that normal? Should I be examining those panels to see if they're working properly? I also ran the system at 40GPM with and without Solar, and got a jump of almost 13 PSI when I turned on the solar, so the problem does get worse with more flow. I tried to let the solar system stabilize to ensure that the flow was not being calculated during the initial water lift. The system was flowing smoothly with no large bubbles at the pool jets, and warm water flowing from them.

I appreciate all of the advice I've gotten so far, and I hope that you guys will continue to have sage guidance for me. :)

Data:
Empty Filter (No Filters or DE), No Suction Crawler, Solar Bypassed
Flow/RPM/Power/PSI
85/3230/2300/13.5
65/2485/1090/8
45/1860/500/4
40/1760/430/3.5
32/1435/265/2

Filter Medium installed, No DE, No Suction Crawler, Solar Bypassed
85/3290/2430/14
65/2550/1160/8
45/1920/538/3.5
40/1800/450/3
32/1445/268/1

Filter Medium and DE installed, No Suction Crawler, Solar Bypassed
85/3320/2478/14.5
65/2570/1183/8.5
45/1930/545/3.5
40/1810/457/3

Filter Medium and DE installed, Suction Crawler Installed, Solar Bypassed
60 Not Possible to attain. Reached Max power (3450RPM).
40/2070/616/3
32/1790/420/2

Filter Medium and DE installed, Suction Crawler Installed, Solar Active
40/2875/1295/16
32/2340/750/10
 
The PSI rise for solar panels will be higher with a VF pump than a fixed RPM pump because the flow rate is the same with a VF while the flow rate drops with other pumps but even taking that into account, the head loss seems high to me too. By my estimates, your panel head loss is about 10x what a normal system would be.

Also, what is the height of the VRV relative to the filter pressure gauge? The pressure at the VRV will still need to be positive in order to keep it closed so the pressure you are seeing could be related to the VRV height. In other words, at those flow rates and pressure, you might not have fully primed the panels so what you are seeing is static head.

If you turn up the flow rate and you see more come out of the returns, then the panels are not fully primed. Depending on the height of the panels, you may need more than 40 GPM to fully prime them.
 
The panel tops are about 15' above the pump level (on the roof of a single-story home). The VRV is probably about 11' above the filter pressure gauge, given a pressure gauge about 4' off the ground. I believe that the panels were fully primed at 32GPM, as I did not hear the sounds of water entering the VRV, and the flow was bubble-free. However, I didn't examine it super-closely. Thoughts?

I am planning on having a professional re-working of the solar soon, so knowing that the system is not functioning properly points me toward having him ensure proper functioning. If I can expect a properly working system to generate 1PSI of head, that guides my decisions now that that the other filter issues are resolved.
 

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You really need to increase the GPM just to make sure that the lines are fully purged. Even if you don't hear water from the VRV, that doesn't mean the pipes are fully purged.

At 11' the minimum filter pressure needs to be 5 PSI plus a little margin for the pressure loss to the VRV. However, there is also a minimum flow rate required to purge air down a pipe. The air wants to rise in the return pipe so it takes a significant amount of flow rate to push the air downwards. I have found that a minimum of 45 GPM is required for purging the pipes so yours may not be much different. But I am pretty sure that 32 GPM is not enough.

Try this experiment. Set the pump for 50 GPM without solar and record the filter pressure. Turn solar on and record the filter pressure again. Post both of those here along with the pump RPM. My guess is that the pressure rise as a percent of nominal, will be less. If pressure rise as a percent is about the same as before, then there is probably something wrong with the panels and/or plumbing.
 
I did the experiment, as you suggested. It looks like the pressure rise is about the same as before, if not more. Here's the data:
Solar Bypassed: 50 GPM, 2020 RPM, 620 Watts, 5 PSI
Solar Active: 50 GPM, 3040 RPM, 1595 Watts, 23 PSI

I left the pump running for 10-15 minutes before taking the second measurement to ensure that the system had had time to stabilize. Is this consistent with a problem with the panels or plumbing?
 
Yes, it is looking more like an issue with the plumbing and/or panels. The hard part now is trying to figure out what is causing it. The first place to check is the check valve on the solar return, assuming you have one.
 
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