Solar heater pipe sizing

[n240sxguy]

I'm getting ready to run the pipe for a future solar heater addition. The run is around 150-160ft each way from the pad to the roof. What size pipe would be best for that? I got a price for 2", but after measuring it, I wonder if bigger would be better. I don't even know if the local supply house has anything bigger than the 2" that I had them price. I'm planning to pick it up, and run it tomorrow, so what is the ideal size?


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[pooldv]

2" is fine. 150 horizontal feet at 50 gpm is only 6' of head loss.

 

[n240sxguy]

Ok. Thanks.


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[mas985]

A couple of questions to make sure you won't run into any issues.

What is the current filter pressure without solar?

What size is the multi-port valve on the sand filter? 1.5" or 2"

Approximately how many 90's will you be using to get to and from the panels?

How high above the filter with the panels be installed?

What is the model number of your pump?

 

[Sammy2]

I always add 10% for head loss due to fittings in addition to actual head loss do to length and vertical rise. Of course the more fittings and elbows as Mark is alluding to the higher the additional loss.

Working in your favor is the fact that PVC has a very low Reynolds number so losses due to length are pretty low.

I could be wrong. I have been before.

 

[mas985]

Reynolds number is not dependent upon the roughness of a pipe. It is only dependent upon hydraulic diameter of the pipe and velocity of the water. You may be thinking of friction factor which is dependent on the pipe roughness.

But 10% is a bit low in my experience for fittings. Usually fittings make up close to a 1/2 of the head loss in a single run (e.g. 5 90's + 30' of pipe) but it does depend upon the run. Usually, the longer the run, the more fittings involved which made me a little concerned in this case.

 

[n240sxguy]

Current clean pressure is around 13-14. 2" multiport valve. The run I'm putting in will have 3 90's on each run just to get into and out of the ground. I suppose there will probably be 2-3 more per side once all is said and done. The panels will start probably 10' above the pump, and run up a 9/12 roof from there. The pump is a waterway mustang pump. Svl56 is their current model number which is a direct replacement for mine.


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[mas985]

The panels will start probably 10' above the pump, and run up a 9/12 roof from there.

What will be the maximum height?

Also, can you describe the suction side of the plumbing, number of runs, pipe size and distance to pool?

Lastly, what will be the total area of the panels?

 

[Sammy2]

Reynolds number is not dependent upon the roughness of a pipe. It is only dependent upon hydraulic diameter of the pipe and velocity of the water. You may be thinking of friction factor which is dependent on the pipe roughness.

But 10% is a bit low in my experience for fittings. Usually fittings make up close to a 1/2 of the head loss in a single run (e.g. 5 90's + 30' of pipe) but it does depend upon the run. Usually, the longer the run, the more fittings involved which made me a little concerned in this case.

It's only been 25 years since doing hydraulics so I'm a bit rusty on the subject and probably in general.

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[n240sxguy]

What will be the maximum height?

Also, can you describe the suction side of the plumbing, number of runs, pipe size and distance to pool?

Lastly, what will be the total area of the panels?

If the 10 ft start is correct, the total height would be 19ft if I use 12ft panels. Suction side has an individual 1.5" run from each skimmer, and the main drain tied into a 2" header at the pump. Pad is about 20 ft from the deep end of the pool. Panels look to be around 300 sq. ft.


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[mas985]

Best I can tell it should work ok with 2" pipe. Pressure rise should be around 5 PSI with 100% of the flow going to the panels with pressure to spare. Flow rate would go from about 84 GPM without solar to 63 GPM with solar so plenty of margin and you should be able to bypass some flow around the panels if you want to since you have 5 PSI at the top of the panels.

 

[n240sxguy]

Ok, here's more accurate numbers on the height. The bottom of the panels will be at about 12.5ft, so the top will be at 21.5ft with 12ft panels. I wonder if low speed on the pump would be able to work after they were primed on high? Guess I'll have to wait to find that out for sure.


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[mas985]

The only way it could possibly work on low speed is if you put the VRV on the supply side of the panels.

 

[n240sxguy]

Ok. I'll explore all the details when the time gets closer for installation. Probably next summer. Really hoping for this summer, but I don't see that happening.


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[n240sxguy]

What type of wiring does an auto solar controller have? Just main power, valve control, temp sensors?


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[mas985]

If you plan on running on low speed, you need one that will prime the panels on high speed and then automatically step down to low speed. Few stand alone solar controllers support two speed pumps in this way. However, the more advanced multi-purpose controllers like AquaLogic, will do this. Setting up for low speed solar is a bit tricky.

Read this: Dialing in VS Pump RPMs when running solar

 

[n240sxguy]

I guess it is a tricky proposition. What are the requirements for the panel temp sensor? Do I just run a pair of #12 or #14 wire over to the panels, then tie the temp sensor into that to run back to the controller? Any problem running it with the wire going to my pool light switch by the house, then just run it through the box and up when the time comes?


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[pooldv]

It is a 10k ohm temp sensor, use a black one so it picks up solar heat gain. Install it next to the panels. Run 20ga twisted pair back to the controller. No issue running it in the light conduit.

 

[n240sxguy]

I'll have to see if I can find that anywhere around here.


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[n240sxguy]

It is a 10k ohm temp sensor, use a black one so it picks up solar heat gain. Install it next to the panels. Run 20ga twisted pair back to the controller. No issue running it in the light conduit.

You talking about doorbell wire?


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