No hot water - seems to be working

[JohnNash]

Hiya

Have a solar tube array on the roof.
Closed system with glycol, heats up the water tank through a heat exchanger.
Tank feeds into the main boiler on demand
Suntana 2 controller.

The pump is working, warm itself, and the controller turns it on and off based on tank/collector temp difference. Pressure is up to about 4bar (which I think is water pressure)
The tank sensors are showing a constant 17-19 degrees although the collector sensor is up to 90 degrees at the moment (very sunny for the UK) and their pipes are cold.

A few weeks ago, I noticed that the tank sensor cable was broken and that the controller was showing an interruption. I resoldered it and all was good but then noticed that water isn't getting hot. The collector isn't overhearting or blowing out and there are no puddles of glycol on the roof (it did this when we moved in as the fluid hadn't been changed in years).

I changed the sensors anyway - no change.

I know nothin about these things, there are various valves and taps in the cupboard and I have no chance of getting someone out during the lockdown period and am worried about the thing overheating.

Would a picture help ?

Thanks for any help

worried of herefordshire

[LucMan]

Sounds like heat pipe failure in the evacuated tubes. Do a search for checking and repairing heatpipes.

[JohnNash]

I had a search and I couldn't find anything on how I can check these ?
The roof is accessible so it will be easy to do a visual ..

[LucMan]

The evacuated tubes need to checked with an infrared thermometer, the heat pipes can be checked visually for cracks or splits at the base. It was discussed here several years ago.
https://www.solarpaneltalk.com/forum...vacuated-tubes

Consider yourself spoon fed.

[JohnNash]

Well.

To the next person that hits this thread with similar problems amd to save yourself hours of reading material, then here is a summary which may help you: My array was very simple, which I think most appear to be (the internal plumbing is more of a challenge). A closed loop, with a heat transfer fluid of a glycol mixture (on mine) which is pumped around the array, feeds into a heat exchanger loop in the hot water tank. The pump gets turned on and off by the controller based on the temp difference between it's sensors, one in the array and two in the tank. If the array is hotter than the tank then the pump runs (looks like 10 degrees c on mine). That's about all the controller does on mine although it can run bypass valves and stuff for more than one tank
There should be a feed loop and drain on the closed loop handling the heat transfer fluid, so you can flush. I also learned from youtube and by trial and error that you can fill the loop from the top through the valve https://www.youtube.com/watch?v=wjttxqPip9k

What happened to mine appears to be that a tank sensor failed at some point, and I didn't notice (it's in a cupboard), and the controller wouldn't turn on the pump. I think what has then happened is that the array super heated the mixture and eventually blew one of the washers on one joint which links the banks of collectors. It must have happened a while back as all the glycol has been rained off the roof.
The pressure gauge was faulty and stuck at 4 bar too !

I linked a tap to one of the filler loops and basically flushed the remains of the coolant fluid out, which identified the failed joint.
My plan is to repair the joint and then flush with water completely and then fill with water (it is summer) to check operation and then (before winter) drain it out and refill with a glycol mixture.

The hardest part here was identifying where all the pipes went, so i could fill and drain the array.