Dedicated Solar pump Help

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
New user, but have been reading advice here for sometime..

I am having to get a new roof on my house, I had the solar panels pulled for the job. I am planning to build a rack system instead of putting them back on the roof. My question is on a dedicated pump (main pool pump is on the opposite side of the house of where rack needs to be)

The only part of this I am knowledgeable about is the electrical end, and the rack mechanics, so if I say something STUPID no laughing lol..

I have 10 Fafco 4x12 solar panels, supply piping will be roughly 25'.. close to that on the return. (I may drop one panel because it will be facing a much better direction on the rack)

If I understand what I have read here, the solar panels will be more efficient with higher flow, but since I will have to ad a dedicated pump, I am actually more concerned with the added electrical for the pump (I already have 2 running, 1 for pool, 1 for spa) so this will make number 3 arghh.

I would like to use 1 1/4 pipe if possible (solar has 2" header).. I am at a loss as to the pump GPM/HP I should be looking at.. I am not planning on using an actuator like it had on the roof, but was planning on using a sensor to pull in a small motor relay if panels were warm, but off on cloudy/rainy days.. will have to add filter to keep panels clean I guess also.

Any advice on the on pump size/gpm/hp would be GREATLY appreciated !!!
Thanks!!

Randy
 

ajw22

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Welcome to TFP.

@mas985 or @Dirk may have the best answers for you.
 

hwy17

Well-known member
Mar 17, 2021
175
Northern California
I don't see a compelling reason for an aux pump. You need filtered water going to the panels or they will clog so a separate pump would need to either have it's own filter system, in which case you might as well just relocate your main pad since you're building a whole new one, or it would need to draw from your existing pad in which case there's no reason for the aux pump.

For 480 sq ft you want something like 55gpm but 40 would probably do. So it's just a matter of calculating the head loss for distance, fittings, and panels to size your pump and piping. 1-1/4 surely won't do you're looking at 2", 2-1/2" or maybe even 3". Then potentially a pump upgrade if necessary but I doubt it.

If you draw a detailed diagram of the plumbing from pad to panels and an exact model for your pump we could help with that.

The panels should be located on the rack at a higher elevation than the water level in the pool if you want self draining freeze protection. Panels will freeze under the slightest frost so they must either self drain or be on a freeze protect auto run unless you live in the deep south. Edit: Ah, Orlando. Well installers still strongly suggest panels should self drain so they don't sit full and stagnant in the sun when the plastic gets soft.
 
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mas985

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I agree with the above that a separate filter will be needed.

1 1/4" is a bit of an odd ball. Why so small? The panel will require about 48 GPM which would have a water velocity of over 10 ft/sec in 1 1/4" plumbing. Very high water velocity results in very high head loss and very low efficiency. I would not use less than 2" pipe so you can go with a lower head pump.
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
I don't see a compelling reason for an aux pump. You need filtered water going to the panels or they will clog so a separate pump would need to either have it's own filter system, in which case you might as well just relocate your main pad since you're building a whole new one, or it would need to draw from your existing pad in which case there's no reason for the aux pump.

For 480 sq ft you want something like 55gpm but 40 would probably do. So it's just a matter of calculating the head loss for distance, fittings, and panels to size your pump and piping. 1-1/4 surely won't do you're looking at 2", 2-1/2" or maybe even 3". Then potentially a pump upgrade if necessary but I doubt it.

If you draw a detailed diagram of the plumbing from pad to panels and an exact model for your pump we could help with that.

The panels should be located on the rack at a higher elevation than the water level in the pool if you want self draining freeze protection. Panels will freeze under the slightest frost so they must either self drain or be on a freeze protect auto run unless you live in the deep south. Edit: Ah, Orlando. Well installers still strongly suggest panels should self drain so they don't sit full and stagnant in the sun when the plastic gets soft.
The only place the rack can go is completely on the other side of the house, so it's not auxiliary,. I should have mentioned that it will have it's own small cartridge filter.

They main reason for doing this is I DO NOT want it back on my roof, and my wife won't do without it lol.. The panels leaked constantly and the chlorine ruined the roof (even with the manual isolation valve it still got up the return somehow)

The panels will be higher than the pool, just not by a lot (probably 3 to 4 feet)

The only thing you said I don't fully understand is about 2-1/2 or 3" pipe?.. I get it that you are saying 1-1/4 is too small, but the factory authorized dealer originally installed this on the roof with 2", so I would think that would be the largest I need to go?
(If I am reading correctly :)

I have a picture that won't help with calculations, but might show you what I mean as far as location.. will attach it below.. The supply and return lines will feed right into the pool but about 10' apart (have a stone garden at the side, and the supply/return will be on each side of it)

Thanks for your help!!!
 

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Rush62

Member
Apr 10, 2021
11
Orlando. Florida
I agree with the above that a separate filter will be needed.

1 1/4" is a bit of an odd ball. Why so small? The panel will require about 48 GPM which would have a water velocity of over 10 ft/sec in 1 1/4" plumbing. Very high water velocity results in very high head loss and very low efficiency. I would not use less than 2" pipe so you can go with a lower head pump.
Well it sounds like I will have to grit my teeth and go 2"... I need to fix the picture I just sent, it didn't have the supply return lines in it...
The supply/return lines are actually going to be visible. that's why I wanted to go smaller, they will run a couple feet alongside a stone garden, and the rest will be below ground (my pool is actually lower than ground, if it were not enclosed by a wall rains would flow in it)

So if I do go 2", and pump is strictly to move water through the panels (and filter), then I should look at a pump that moves at least 48 GPM correct??

Thank you for your help!
 

hwy17

Well-known member
Mar 17, 2021
175
Northern California
After putting panels up myself this year (on an outbuilding) I totally get why you wouldn't put it back on the roof. So many penetrations, they move around as they warm up and cool down rubbing the shingles, mine haven't been up long enough to see any chlorine damage yet of course.

Helpful visual there. Personally I would still be trying to run that system off the main pump. I would trench pipes all the way from the existing equipment over to the rack. Because it's such a long distance is why I say 2-1/2" plumbing might be in consideration. Would have to do some calculations to see if it's necessary or if 2" is good.

What would the suction and return be for your idea?
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
After putting panels up myself this year (on an outbuilding) I totally get why you wouldn't put it back on the roof. So many penetrations, they move around as they warm up and cool down rubbing the shingles, mine haven't been up long enough to see any chlorine damage yet of course.

Helpful visual there. Personally I would still be trying to run that system off the main pump. I would trench pipes all the way from the existing equipment over to the rack. Because it's such a long distance is why I say 2-1/2" plumbing might be in consideration. Would have to do some calculations to see if it's necessary or if 2" is good.

What would the suction and return be for your idea?
You should see the pictures I have after the panels were removed, the shingles were worn conpletely through the first layer.. I can't believe it was not leaking worse than it was!..

But I am not trenching to the old system, (I should have taken more time on the picture).. The panels will have their own supply/return, so the existing pool location won't have any effect, the panels will be totally separate from any of the current piping..
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
After putting panels up myself this year (on an outbuilding) I totally get why you wouldn't put it back on the roof. So many penetrations, they move around as they warm up and cool down rubbing the shingles, mine haven't been up long enough to see any chlorine damage yet of course.

Helpful visual there. Personally I would still be trying to run that system off the main pump. I would trench pipes all the way from the existing equipment over to the rack. Because it's such a long distance is why I say 2-1/2" plumbing might be in consideration. Would have to do some calculations to see if it's necessary or if 2" is good.

What would the suction and return be for your idea?
Ahhhhh I miss read something.... If I retrenched and jacked the pipe size up, you are saying the long run from the existing pump/filter would be ok.... ? I never really considered this.... whew long run though, but worth considering for sure, great now you have my brain spinning again lol..
 

hwy17

Well-known member
Mar 17, 2021
175
Northern California
My panels are 4x20 so the expansion and contraction movement is so great that you can watch bottom headers get pulled up about an inch right before your eyes when the system turns on. I've put some pieces of aluminum flashing under the connectors to keep them rubbing through, but in my case it's just a carport roof so I'm less worried about it.

All of my comments in this thread have been on the subject of trenching from the existing pad so if you're decided against that you can disregard everything I said.
 

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hwy17

Well-known member
Mar 17, 2021
175
Northern California
Yeah if you can get a list of the rough distances and number of 90's or 45's we could try to get an idea of whether it's feasible, and what size pipe it would take.
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
My panels are 4x20 so the expansion and contraction movement is so great that you can watch bottom headers get pulled up about an inch right before your eyes when the system turns on. I've put some pieces of aluminum flashing under the connectors to keep them rubbing through, but in my case it's just a carport roof so I'm less worried about it.

All of my comments in this thread have been on the subject of trenching from the existing pad so if you're decided against that you can disregard everything I said.
And that is what I had in mind (with the aluminum) If I were forced to go back to the roof.. under ever joint unfortunately..

Honestly I guess I was thinking it was too long a run from the existing equipment in the back of my head, so I never really considered that until you brought it up... I AM CONSIDERING IT NOW lol...
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
Yeah if you can get a list of the rough distances and number of 90's or 45's we could try to get an idea of whether it's feasible, and what size pipe it would take.
I am goin to look at photos I have of existing equip... and maybe do a layout to get the info, If that takes a lot of time to figure out, I would not want you to go to that extent (I can take experienced opinions, but that sounds like a lot of time.. ???
 

hwy17

Well-known member
Mar 17, 2021
175
Northern California
Here's a guide on how to do it, but they don't have numbers for pipe greater than 2".


So say for example it's 300 feet round trip and there's 12 90's total involved which makes it equivalent to 400ft, which is a head loss of 16.64 ft at 50gpm and 2" pipe.

Now then you have to try and calculate the head loss in the panels themselves and the equipment at the pad and the plumbing back to the pool and it all kinds of gets too complicated to truly accurately calculate. But what you can at least establish is that the head loss from the long pipe runs themselves is not actually that crazy. And then if you pull up a performance curve for your pump like this you might find that an additional 15-20ft of head isn't too much for it to handle:

 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
Here's a guide on how to do it, but they don't have numbers for pipe greater than 2".


So say for example it's 300 feet round trip and there's 12 90's total involved which makes it equivalent to 400ft, which is a head loss of 16.64 ft at 50gpm and 2" pipe.

Now then you have to try and calculate the head loss in the panels themselves and the equipment at the pad and the plumbing back to the pool and it all kinds of gets too complicated to truly accurately calculate. But what you can at least establish is that the head loss from the long pipe runs themselves is not actually that crazy. And then if you pull up a performance curve for your pump like this you might find that an additional 15-20ft of head isn't too much for it to handle:

I will get the distance and, and get close on the 90 + 45's... (can't be spot on, because I am still fine tuning my rack design)

I feel fairly intelligent until that pump curve / head pressure comes in... then I just jump over to the stupid lane lol.. The long haul distance will be pretty easy, I have my whole house/pool/screen designed in 3D to spec... everything right down to my windows was measured when I did the modeling, so I can measure it from that..

I am going to check those links you posted tomorrow and see if I can grasp it accurately...

Thank you sir
 

mknauss

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Check out the signature of mas985 -- post #4 above. He has spreadsheets linked in his signature for pipe/pump calculations.
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
Here's a guide on how to do it, but they don't have numbers for pipe greater than 2".
Man, your 300' was almost spot on.. It looks like 165' on supply and 125' on return... will add 20' at the rack so round trip would be approx 310'
And your 12 90s' total is just as close, (if I can get away with using 45's anywhere I will) but 12 to 14 is going to be real close.
I used the tax assessors web site to get the measurements.

So I am going to go through the links and information you guys gave me, and see if I can get a grip on the formula to pin this down.

I really appreciate all the help from everyone, you guys are awsome!
 

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mknauss

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A thought -- why not install a heat pump and PV solar? Generate your electricity and use the heat pump to maintain the water temperature.
 

Rush62

Member
Apr 10, 2021
11
Orlando. Florida
A thought -- why not install a heat pump and PV solar? Generate your electricity and use the heat pump to maintain the water temperature.
I was floored when I saw how many panels I would need to power my main pool pump, I can imagine what I would need to power a heat pump..
Lord knows I will look into it out of curiosity though :}
 

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