Solar heating question

[vbgagnon]

Hi, I'm new to your forum. I searched but could not find the answers I was looking for.

So here goes...

I have a 24 ft round above ground pool which is not setup yet, but I want to get all my things in order before I begin to set everything up. I would like to get some solar pannels to heat the pool, but the only place that I could put them so they would get useful sunlight would be on the roof. While this is usually not a big deal, but I've got to put the pannel on the second story of my house.

I've done some measuring and I've got to go about 20 ft stright up and then another 8 or so ft along the roof to where the pannels would be mounted. My pump/filter setup will be about 25 ft from the house. So i've got a long and high run to take care of.

My pump is a 1.5 hp Jacuzzi brand. Its about 6 years old and I can't find any specs on it.

So after all this gibberish here is my question: Will my pump be able to handle the load?

[CarlD]

I don't know. I don't know how to figure "head". But the Hayward web site has a document on how to compute that, and Jacuzzi may be able to help figure our the pump's specs.

But...unless you are planning to remove the solar panels every fall, you'll need to have a draining system built in to ensure water doesn't freeze in them.

[mas985]

Assuming your pump is one of these, it should have enough head to prime the panels. However, the head loss in the pipe runs will slow down the flow rate so use at least 2" pipe if possible.

[cleancloths]

1 PSI is equivalent to roughly 2.3 feet of water column.

[Poconos]

Normally with the panels close to pool water level you can put a bypass valve in the line to allow most of the water to bypass the solar. You get more overall flow and there is still enough water going through the panels to operate efficiently. However, 20' in the air and with a relief valve at the high spot to allow them to drain, you will probably have to run the entire flow through the panels which will cut the overall flow rate. If you bypassed any of the flow there would not be enough pressure in the solar lines to prime them. Just be aware of this.
Al

[cleancloths]

How does that relief valve work? I ask because the elevation should only come into play to start the flow, once you have it established you are taking water from grade and returning it to grade, thus the only pressure you need is to overcome friction losses due to the length of pipe and equivalent length of the fittings.

[mas985]

That's correct. Elevation only comes into play during priming. The valve remains open until water reaches it then closes off. At that point, the pump still needs to push out the remaining air through the returns so it still needs to overcome elevation head plus the dynamic head where the water is in the plumbing. Once the solar return pipe is full of water, the elevation head is then canceled.

But because of both the solar pipe and panels, there is quite a bit more dynamic head loss with solar than without. If there is not enough pressure at the top of the panels to keep the VRV closed, it will open and suck in air thereby removing the canceling effect. The pressure at the top of the panels is always dependent on the elevation rise so it will always be lower than the pad pressure by at least height / 2.31. So for a 25' roof, the pressure will be at least 11 PSI lower than the pad and that doesn't take into account the extra pressure loss due to dynamic head.