solar panel plumbing problem

dustygroundhogNovember 18, 2012

Wondering if anyone could give me advice on a problem I have run into in connecting some new solar panels into an existing set of solar panels I now have connected to my pool?

My problem is at the t shaped junction point between the

1 1/2" pvc pipes which return heated water to my pool after it has run through the two separate sets of panels. I installed a flow control valve on each of the pipes leading from the panels to the T junction. I also installed a flow meter on each pipe so I could see how much water was flowing through each panel and equalize the flow rates (or get higher flow from whichever bank of panels is better oriented toward the sun at a given hour of the day). Unfortunately, no matter how I set the flow control valves on each pipe 100% of the flow goes through one pipe and none through the other. In other words, no matter how slowly I open one valve and close the other, instead of the flow from one set of solar panels slowly increasing and the other decreasing until the desired balance is reached, the flow remains 100% from the A set of panels and 0% from the B set until a certain point is reached, then it switches instantaneously to 0% from A and 100% from B, with no setting where there is flow through each set simultaneously.

The only thing I can figure out is that the flow from set A into the T junction completely blocks the flow from set B until the flow balance between A and B reaches a certain point, then the blockage reverses. This seems completely counter intuitive to me and I am looking for advice as to how to rectify the situation.

Does anyone know whether installing a flow direction check valve on each of the 1 1/2" pipes returning water from each set of panels would solve the problem of one flow apparently blocking the other?

You should probably also know the following: 1)Water flowing from the pool pump to each set of panels goes through a 1 1/2" pipe which is separated into two 1 1/2" pipes at a T junction identical to the one that rejoins the two flows after they go through each set of solar panels: 2) There is a bypass Jandy valve located on 2" pipe running between the pool pump and the 2" pool return pipe. This allows regulation of the total flow of water into the 1 1/2" pipe leading to the two solar panels so that flow to the panels can be entirely shut down: 3)There is almost zero room in a confined space in which the pool pump, filter, and plumbing are located so that replacing the 1 1/2" pipe currently leading to and from there to the solar panels would be almost impossible. It did occur to me that the 1 1/2" return pipe leading from the T joint back toward the pool might be too small to handle the water from the two 1 1/2" pipes flowing into it. However, since those two pipes are fed by a single 1 1/2" pipe from the pump why wouldn't a single 1 1/2" pipe also be adequate to handle their return flow?

It's all a mystery to me. Can you help?

Thanks for any help you can offer.

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How many vacuum relief valves are in place?
Where are they placed?
Are both panel sets at the same or nearly the same elevation?
How high are your panels?
How much difference, in feet, are the pipes leading to each panel set?
Are they both at the same angle of inclination?
Are you feeding the panels from low to high?
Why aren't you feeding both sets at the same time, all the time?


    Bookmark   November 19, 2012 at 4:35AM
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There is a vacuum relief valve on one set of 9 2x10 panels which are mounted vertically on a 45 degree A frame type "lean to" structure running from a roof to the ground. The intake for these panels is 2' above pool level and the return is at about 8' above pool level. The vacuum relief valve is placed at the 8' level as per Sungrabber installation instructions.

The second set of "panels" is not really a set of panels. It is actually a pre-existing set of four 1000 foot coils of 1" black plastic well pipe which are located on a large, flat garage roof. These four coils are linked to the pool system via two manifolds which are fed by the same 1 1/2" pipe which feeds the solar panels.

The problem I describe occurs after the return flow from these coils passes through their return manifold into the 1 1/2" pipe and reaches a point about 2 feet beyond the manifold where this 1 1/2" pipe rejoins an identical 1 1/2" pipe coming from the solar panels. There is no relief valve on the four coils.

The four coils lie flat on top of the garage roof at an elevation 8' above the pool level. The return flow from the solar panels is also at this 8' elevation, as is the T joint connection between the panel return flow and the coil return flow.

The 1 1/2"pipe leading from the pool pump to the point at which it splits to feed both the panel and coil systems is about 12' long and rises about 6' above the pump level. The pipe from this split to the manifold feeding the four coils is horizontal and about 2' in length. The pipe from this split to the point at which it enters the nine 2x10 panel array is about 24' long and drops about 6'.

The set of panels is fed from low to high. The four coils are all on the level roof.

I am feeding both sets at the same time all the time because each is fed from the same 1 1/2' pipe. The flow through the panel system and the coil system respectively is, however, regulated by flow control valves located on each system after the water flows through the system but before it reaches the problem T joint at which the water from each system merges for its return trip to the pool below. I installed these flow control valves after I discovered that water from one system was blocking the return flow from the other system in the apparently mistaken belief that by slowing the return flow from one system I could balance it with return flow from the other system so that each would contribute equally to the overall return flow of heated water to the pool.

The four coils on the roof were in place at this location prior to the installation of the solar panels which are intended to augment them for additional wintertime heating. The pool is located at our vacation place in the SoCal desert. I would post a picture of this rather odd system, but we are not in the desert now. I am preparing for our trip there next month when i will attempt to fix the problem I am trying rather poorly to describe.


    Bookmark   November 19, 2012 at 8:25AM
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The 1"x1000' coils are introducing a large head loss. This is far more than the panels and creating the problems you are experiencing.


    Bookmark   November 21, 2012 at 2:05AM
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