Solar hot water fault

[Chris_909]

Hi,
Got solar hot water tubes on the roof, don’t know much about them but they don’t seem to operate correctly, when there turned on the raydan controller temp display is very sporadic and jumps around and occasionally the relay which controls the circulation pump is constantly clicking on and off,
regardless of that happenning the pump gets red hot.
I’ve checked the temp sensors and they seem to be giving me a correct reading when measured.

Anyone got an ideas?

 

[Johntheo5]

You should see a pressure gauge somewhere near the solar circ pump which should read somewhere between 1.5bar & 2.5bar, certainly not lower than 1.0bar.

 

[Chris_909]

You should see a pressure gauge somewhere near the solar circ pump which should read somewhere between 1.5bar & 2.5bar, certainly not lower than 1.0bar.

Yeah reads normal, 1.5 bar

 

[Johntheo5]

If, and you should, be able to run the circ pump manually, do so, and see if the relay stays closed/pump keeps running.
The heart of any Solar controller is its differential temperature control where it monitors the collector(s) outlet temperature and the "store" temperature which is taken from a probe inserted in the HW cylinder just above the top of the solar coil, when the diffetential temperature approaches ~ 10C/15C, the circ pump cuts in and when the differential temperature falls to ~ 3C to 5C, the pump cuts out, some systems have a variable speed pump to maintain, as long as possible, a differential temperature of say 6C/7C, my non variable speed flat plate system has start/stop differential settings of 7C/3C.. Check these settings as well. Post emanual for your system.
You could possibly have air build up in the top of the collectors but this normally shows up as excessive collector temperature.

 

[Chris_909]

If, and you should, be able to run the circ pump manually, do so, and see if the relay stays closed/pump keeps running.
The heart of any Solar controller is its differential temperature control where it monitors the collector(s) outlet temperature and the "store" temperature which is taken from a probe inserted in the HW cylinder just above the top of the solar coil, when the diffetential temperature approaches ~ 10C/15C, the circ pump cuts in and when the differential temperature falls to ~ 3C to 5C, the pump cuts out, some systems have a variable speed pump to maintain, as long as possible, a differential temperature of say 6C/7C, my non variable speed flat plate system has start/stop differential settings of 7C/3C.. Check these settings as well. Post emanual for your system.
You could possibly have air build up in the top of the collectors but this normally shows up as excessive collector temperature.

Okay so there’s a test button which doesn’t seem to do anything and a DIF test, when I slide this the pump kicks in and sounds like water is flowing, when I test both at same time the pump is on but the temp display disappears,
There’s settings to adjust the degrees and the differential(1-10) when I lower the degrees it sorta sounds like the relay is failing? But surely if the relay is failing then the pump wouldn’t come on at all?
Unfortunately I have no info on it, the previous owner left nothing, and I can’t find any info on the internet

 

[Johntheo5]

Difficult to say what the problem is withoout the controller MIs, you could disconnect the pump cable from the relay and see if the controller then behaves normally. If you are happy that the two sensors, the collector outlet and the store temperature are giving steady and accurate readings then you might consider buying a new controller like a Resol which seem popular, I have a (15 year old) Lago SG2 controller. I have PT1000 sensors which have never given a problem. If you do opt for a new controller ensure your sensors are compatible with it. Its surprising the internet doesn't throw up some info on your controller though?.
Maybe worth joining one of these solar forums, sometung like this......might get some info via this.

https://support.smallsolar.co.uk/portal/en/home/

 

[ericmark]

My daughter has solar water heating in Turkey, and it works well, but the father-in-law had it in North Wales, and we never did get it to work. In my house in mid-Wales we use PV panels, and an immersion heater that will heat DHW before we export electric, that works well.

I could not find a fault with fathers-in-law installation. All seemed correct, but never worked except to remove chill. New owners ripped it off.

 

[Johntheo5]

Interesting, I have a very modest 2 X Flat Plate Array, 4 m2 (3.86) , (self installed), the yearly solar radiation here (Cork) has varied very little over the past 15 year period at 950/1050 kWh/m2 and the solar controller monitors the output which gives a almost steady 1000 kWh/annum (25/27% efficiency), I would expect a E.tube array of similarsize to give maybe 25% more output, useful in the spring/autumn. I went for the F.plate as I have very soft water and set the max HW cylinder temperature to 85C (with a TMV set to 60C on the outlet), the system never reaches stagnation temperature as the F.plate loses at very high collector temperatures means I have never seen a cylinder temperature higher than 79C.

 

[ericmark]

I am sure my fathers-in-law set up was faulty. But it never worked as it should have done, in my opinion.