Air Gap in Pump Filter with Solar Panels

[goody222]

[FONT=&quot][/FONT]Hi, For my 25k in-ground pool, I have a SP3210X152 TriStar 1.5 HP Pool Pump (Max Rate, Two Speed) which normally ran fine at 10psi in high speed with a clean filter.

After having a solar system installed, the pump now runs fine at 13.5psi high speed with the diverter valve bypassing the solar cells (3.5 extra psi due to the check valve, additional elbows and diverter valve I assume?). When flow is directed TO the solar panels (2 story roof), pressure increases to 26psi in high speed (company says expect a 2-15psi increase which I'm within).

The problem is with 26 psi going to the roof, a 1" air gap in the filter basket develops. Air doesn't seem to be getting in the pump suction, but I was told the filter basket should always be full in High Speed. This never happened at 10psi and doesn't happen at 13.5psi (flow bypassing the solar panels) - the air gap only shows up when pumping up to the solar panels.
The installers said since it is on the inlet of the pump, it has to be an air leak. My pump filter cover is on tight, O-ring is clean, cartridge filter is clean, and all 7 solar panels are rated for a total max flow rate of 77 gpm. Plus its strange that the air gap would only show up at the high pressure.

Would you have any idea why the air gap ONLY shows up at 26psi? Thanks!
-Mark

 

[Spa Owner]

I think this is the pump working as hard as it can and simply 'sucking' more than the pipe can deliver. Proof is easy enough. Place a piece of brick in the hair and lint pot. This displaces some water and I think you will find the 'air' vanishes.

 

[goody222]

Interesting - the brick did eliminate the gap (yes, I took it right out afterward).
FYI: I haven't noticed any bubbles coming from the return jets, nor is there any air at the top of the filter housing when I bleed it. So at least no air is getting in the system when aligned to the solar panels. Thanks Spa Owner.

 

[Rocket J Squirrel]

I would venture to guess that the gap in your leaf pot isn't air - it's vacuum.

Your panels cannot supply water at the rate demanded by your pump's high speed. I know that my own solar panels can't either.

I have a VS pump, but my understanding of 2-speed pumps is that low speed is for the pool and high speed is for the spa. Run your pump at low speed and your solar panels will be happier.

 

[mas985]

[FONT="][/FONT]
The problem is with 26 psi going to the roof, a 1" air gap in the filter basket develops. Air doesn't seem to be getting in the pump suction, but I was told the filter basket should always be full in High Speed. This never happened at 10psi and doesn't happen at 13.5psi (flow bypassing the solar panels) - the air gap only shows up when pumping up to the solar panels.
The installers said since it is on the inlet of the pump, it has to be an air leak. My pump filter cover is on tight, O-ring is clean, cartridge filter is clean, and all 7 solar panels are rated for a total max flow rate of 77 gpm. Plus its strange that the air gap would only show up at the high pressure.

Would you have any idea why the air gap ONLY shows up at 26psi? Thanks!
-Mark

There is a critical flow rate required within the pump basket to remove air. More than likely that air is entering all the time but you only notice it when the flow rate drops due to the higher pressure (i.e. head loss) and it starts to accumulate in the pump basket. Placing a brick in the pump basket reduces the volume in the pump basket which in turn increases the water velocity and can help expel the air out the return. So I think there is probably still a small air leak somewhere and most likely in the pump lid gasket.

However, the pressure rise for solar is a bit high for my liking. This puts the panels under significant pressure even up on the roof. How many panels are installed and what size/length pipe is being used to feed those panels?

More than likely you are pushing too much water through the panels. You could bypass some of the water around the panels to lower the PSI rise. Usually a 3-5 PSI rise is sufficient for solar efficiency.

 

[mas985]

I would venture to guess that the gap in your leaf pot isn't air - it's vacuum.

A pure vacuum would be impossible in a pump basket (or anywhere else) so if you mean a partial vacuum, I would agree. But a partial vacuum still has air, it is just at a lower pressure than atmospheric pressure.

Your panels cannot supply water at the rate demanded by your pump's high speed. I know that my own solar panels can't either.

Solar panels come after the pump (i.e return side) so they do not supply water. However they do resist flow by creating a lot of head loss.

I have a VS pump, but my understanding of 2-speed pumps is that low speed is for the pool and high speed is for the spa. Run your pump at low speed and your solar panels will be happier.

It is very difficult to operate solar panels on a roof with a VRV on low speed. The VRV would need to be lowered to about 6' above the pump to have any chance of working properly on low speed.

 

[goody222]

Mark, The solar panels are Solar Industries. I have 7 that are 12' x 4'. The supply piping is 2" and return is 1 1/2". Its hard to say what the length is - its a 2 story house with 9' ceilings. They told me max flow rate was 11 gpm each although the literature says 10gpm. I'll attach pics.


Oh, the company said with the Hayward diverter valve (GVA-24), there was no way to partially bypass the panels. They also said they usually see a 4psi increase, but that going from 13.5 to 26psi was within the standard 2-15psi expected rise. They told me they left space for an extra panel if I wanted one in the future - if the panels are restricting flow, I wonder if adding one would be better than getting a new pump (which would suck - pool is less than 1 yr old). Thanks!

 

[mas985]

The panels themselves are probably not causing the pressure rise. More than likely it is the plumbing and most of it is from the 1 1/2" plumbing.

You should be able to set the cams in the GVA-24. If you look at the parts, it shows the cams:

https://hayward-pool-assets.com/assets/documents/pools/pdf/parts-diagrams/ActuatorGVA-24.pdf?fromCDN=true

With 336 sqft of panels, you only need about 34 GPM to maintain efficiency so you should be able to bypass quite a bit of the flow rate. Just because you can operate at +15 psi doesn't mean you should.

 

[Poolzzz]

Are the in and out of the panels fed from the same end? Can't quite tell from the picture.

 

[goody222]

mas985, thanks for helping out! I see online/manual how to set the cams for normal operation. Can you second check me on the bypass? => I believe I want the valve handle to point down, which for my "A-2" configuration (Std) I would put the upper cam at 6 o'clock and leave the lower cam (port 2 to port 1 when solar isn't in use) at 12 o'clock. Before I do any of this I believe I can manually use the switch on the back to set it to the bypass to see how well it works. Does that sound right? Oh, and hopefully most of the flow doesn't go back to the pool (path of least resistance).


Poolzzz, not sure exactly what you are asking. Water goes through the pump, then filter, then hits the diverter valve and either goes back to the pool or the panels.

 

[mas985]

Yes I would use the manual switch to find the location where the filter pressure rises about 5 psi or a little less. Then set the cam to the location where the red switch shuts it off. Sometimes it takes a couple tries to get it in the correct location.

 

[Poolzzz]

I was looking at the picture on the roof. It looked like both the inlet and outlet of the solar array were on the same side (right hand side in picture). Is that correct? Or is the output of the array actually on the far left?

 

[Dirk]

Is this of any help?

I have eight 12.5' x 4' panels, and only need 40GPM.

My panels' manifolds are 1.5", but I ran 2" to and from them.

I was taught that the weight of the water coming down off the roof offsets the weight being pushed up to the roof (I forget the name of that principle). And once the system is full that the pump only has to overcome the friction of the water in the system (and the resistance of the panels, too, I suppose), but the supply and return lines mostly cancel each other out, work-wise. Would having each of different sizes mess that up, and reduce the efficiency of delivering to the roof?

I installed a FlowVis for my solar system so I could dial in the flow rate recommended by the manufacturer. Took the guesswork out of adjusting my VS pump (or the bypass, in your case).

I have a check valve on my return line. I suppose that's not necessary, but I saw it in a lot of solar system installation diagrams. The FlowVis is a check valve, so it can serve double-duty in a solar system.

I tilted my array, to eliminate the possibility of trapping air in one of the upper corners of the array. So my panels are 100% full of water, and all the tubes are circulating water for maximum flow and heat exchange. If the OP's panels are trapping air, or water, in addition to reducing the heat exchange, would that also restrict flow, since not all of the panels are allowing full water flow? There's an animation here that illustrates what I'm describing.

And there's a paragraph at the bottom of that webpage that might apply to this discussion...

 

[jblizzle]

I agree it is really hard to tell if exit from the panels is in the upper left like it should be ... well ideally the exit would be upper right and supply would go in lower left.

 

[Spa Owner]

Sorry working metric

2 by 9' plus a bit call it 23' this is 7 metres =70 kPa
13.5 psi is 93 kPa
93 + 70 kPa = 163 kPa
163 kPa = 23.6 PSI

Pressure drop

is probably from​

friction for the balance

Assuming my conversions are in the correct ball park and domestic gear is within normal tolerances I think the pressures being seen are simply from the lift to the top of the panels. The gauge will be registering the pressure from the highest point the water is lifting too.

I guess an easy test to prove, if you can do it. Is turn off pump when system is full of water and close valves so the pressure gauge and the circuit are all full. The gauge will have a reading. This reading is the static head, and I think it likely around 70 kPa (pesky metrics sorry).

A more expensive test is install a gauge in the bottom of the riser pipe to the roof. Pressurise the system shut off so cant drain down and see what the reading is with all pump off.

 

[goody222]

Mas985 – Thanks! I was under the impression that you had to lock the cam in one of the 4 positions. I’ll experiment first with manually setting it and judging performance. Unfortunately I’m away for 1.5 weeks so I’ll have to wait to play around with it.

Poolzzz – both the inlet/oultet lines are on the right side of the picture. I'll have to take a zoomed in picture at some point.

Dirk – thanks for the info. I had the system installed by the biggest solar company in the area that specializes in this, so I’m assuming they know what they’re doing (they do have the angle correct – described it to me in detail).

 

[Dirk]

Mas985 – Thanks! I was under the impression that you had to lock the cam in one of the 4 positions. I’ll experiment first with manually setting it and judging performance. Unfortunately I’m away for 1.5 weeks so I’ll have to wait to play around with it.

Poolzzz – both the inlet/oultet lines are on the right side of the picture. I'll have to take a zoomed in picture at some point.

Dirk – thanks for the info. I had the system installed by the biggest solar company in the area that specializes in this, so I’m assuming they know what they’re doing (they do have the angle correct – described it to me in detail).

Wow. My "expertise" on solar panel installation is based only on how to install my own, but I did read about it extensively before attempting it. I can't now recall ever seeing or reading about a set of panels that had the inlet in the lower corner and the outlet on the upper corner on the same side of the panels. Always opposite corners. Always. And if the panels are skewed in the way I mentioned (as illustrated in that link I provided), I don't see how they could be circulating correctly, and not trapping air or inhibiting proper flow. I don't think that's possible. Depending on which way they're skewed, they'll either trap air, or not drain properly. Do you have freezing temps in the winter? Even if they're skewed to not trap air, I think you'll get more flow through the panels on the right than on the left, as water seeks the path of least resistance.

The different sized pipes, the missing check valve, the missing bypass for a non-VS pump, could all be "yellow" flags based on my studies. I think the bypass can be handled by the existing valve, as you've been discussing. And the check valve seems to be optional, so maybe no big deal there. But the two different sized pipes is a mystery to me. Do you have a vacuum breaker? Do you have a proper solar-drain-down three-way valve? If not, those are other suspects. Those two PVC ball valves are also a sign of less than high-quality work.

One thing I've learned here at TFP, after reading so many build threads, is assuming a contractor knows what he's doing is not always prudent.

Granted, I did come across several ways to install panels. Each installer probably has their own methods and tricks, based on their experience. But what you're describing does seem to be pretty far outside of the norm, corroborated to at least some degree by the fact that your system is not actually working all that well. If you had a pro install, you shouldn't have to be monkeying with pumps and valves and flow rates and pressure. The system should have been 100% optimized by the installer.

Can you share the brand of panels you've got? Perhaps your installation is unique, and correct, for that particular brand.

And is their a "second biggest solar company in the area" that you could ask to come take a look?

 

[jblizzle]

I agree with Dirk. There is no way the solar panels can operate correctly with the inlet and exit on the same side of the panels

 

[Poolzzz]

Poolzzz – both the inlet/oultet lines are on the right side of the picture. I'll have to take a zoomed in picture at some point.

In that case I question the flow through the far left panels. If all the panels are not similar temperature when operating you have a flow problem.

I also wonder if the panels are tilted/skewed. Are they level or is one side higher than the other (ie is the right side higher, same or lower than left?). They look level in the picture which would not be good if you experience freezing.

What flow does your pump produce at 26 psi? I'm not as convinced as Mas that your 13 psi increase can be adequately explained by piping but it depends on flow rate. I do agree the panels themselves should not be contributing much to the pressure increase.

 

[Dirk]

In that case I question the flow through the far left panels. If all the panels are not similar temperature when operating you have a flow problem.

I also wonder if the panels are tilted/skewed. Are they level or is one side higher than the other (ie is the right side higher, same or lower than left?). They look level in the picture which would not be good if you experience freezing.

What flow does your pump produce at 26 psi? I'm not as convinced as Mas that your 13 psi increase can be adequately explained by piping but it depends on flow rate. I do agree the panels themselves should not be contributing much to the pressure increase.

The OP did mention that the panels are tilted/skewed. Assuming he's referring to what you and I are, that skew wouldn't work correctly with in and out on the same side. They'll either trap air or trap water. Both bad.

I think there is a consensus forming... that unless these are "magic panels" that require the supply and return on the same side, they were not installed correctly...

Getting a hold of the panel manufacturer's owner manual or tech support would address this possibility in short order.

I wish I could help more with the pressure and flow issues. I don't know how. That's why the extra $100 I spent on my FlowVis was the solution for me. No math. No guessing. My panels are perfectly optimized to manufacturer's spec's. (Well, within the 2% margin or error of a FlowVis, that is.) I knew ahead of time that $100 was a bargain compared to what it would take me to figure out flow rate, not to mention how to figure out how to figure out flow rate! Just as the OP is experiencing now...