Solar Help!

[Robtheplumb]

Hi
We have a client with a problematic solar DHW system, we think we have the answer to the problems, however would like to put it on here to see what you all think!
The system is a Smart energy set up, 30 evacuated tubes, on a ssw facing pitched roof, convaluted stainlees pipework in siamesed insulation, pumping station in loft, and 1200x450 solar cylinder.
The problem is, that although the system has worked well in the past, over the last couple of years the customer has been experiencing banging coming from the loft, and eventually a faliure of the system.
A collegue of ours has had a look at the system, and ended up stripping and cleaning out the pump and pumping station, on doing this small hard white balls were found to be obstrucing the pump, these were removed, the system refilled, and all was ok for a short while, but now the problem persists.
The controller is functioning as it should, the pump cuts in and out ok, and the system holds pressure.
Our thoughts are that the system is a bit on the tube heavy side, and that it is boiling up during prolonged sunshine and breaking down the fluid due to high temperatures in the system, imho, 20 tubes is more than adequate for this size of cylinder, in this situation.
Would be interested to hear eveyone elses thoughts!

 

[Cds]

I think your assessment is spot on.

 

[sas]

Have you fit that pump back to correct direction. It sounds like you having a water hammer too. Check any valves which might be causing a restriction to flow as this will make the pump work inappropriate way and end up burning the pump.

 

[jon the plumb]

Sound like the fluid is boiling and hammering out the safety valve. Is there a bypass fitted which may be stuck

 

[migoplumber]

last time i found little white balls in a pump, they turned out to be the insulation from the header tank. (white polystyrene lid had fell in and disintergrated.