Solar Panel Controller Problem

The controller should manage the system entirely and you should not use or need a thermostat in addition to this.

The controller is a differential thermostat measuring the difference between the panel temperature and the cylinder temp. When the difference is above (say) 6 degrees, the pump comes on, when the differenece is less than 4 degrees it goes off. If the cylinder goes above a set value (say, 60 degrees) then the pump no longer operates to prevent boiling and then you may find the panel going to 105 or even 205 degrees, but not your cylinder.

Many in the industry (including me) prefer to use some sort of heat dump on the same controller to prevent the panel reaching such temperatures.

It isn't clear what part of your system is going to 105 or what the new thermostat is doing. Can you provide more info?

mise mise wrote: »

The temperature of the cylinder was going to 105 degrees. It is my guess the controller was not wired properly and then the thermostat was installed to the cylinder as a solution to resolve this but it now overides the controller functions. Should a new controller have been fitted or some sort of trouble shooting done before the fitter put on a thermostat.

You probably don't need a new controller. Installing solar requires quite a bit of plumbing, roofing, some electrical work and a dollop of common sense. One or two of these components seem to be missing from your installation. :rolleyes: Most of these problems are installation errors rather than failed hardware, unless it is a really cheap and nasty controller.

I suggest you get another installer to look over the controller as a matter of urgency. If you PM me the brand of it and your approx whereabouts, and it happens to be one I work with, or know who does, I'll point you in the right direction. Getting a new controller may involve replacing probes if they use a different type and that would be a bit of a job.

If you do have to replace the controller, you can assess the type of probe by whether the resistance across the wires is about 1K or 100 ohms, and whether this resistance rises or falls with temperature. You would then look for a controller that uses the same probe - at least on the roof.

The current situation is a mess. There should be a number of separate protections preventing your cylinder going to that temperature, and one single thermostat doesn't leave any redundancy. I am particularly worried because if you got to 105 degrees, that implies that your system is unvented (vented cylinders boil at 100). If that is the case, your temperature pressure relief valve has also failed, and if you don't have an anti-scald valve, the system is downright dangerous.

Further, it is unvented (i.e. not fed by an attic tank) then one dodgy stat is all that stands between you and this. :eek:

Q

Hi,

Perhaps the installer was out to impress and set the controller to read in Farenheit ?

105c should be tipping into the storage tank in the attic in the form of steam or blowing the safety valve on the cylinder if pressurised.

Faulty probe not properly calibrated?

Even the cheap controllers will not read the probes if wired wrong, different resistance.

Agree it needs to be looked at and the problem corrected.

.