Renewable power cannot reproduce base load availability

So under the house I go, we have a system where the hot water tank is fitted in the crawl space under the house at the end where you can easily stand. Now a quick touch test of the return pipe where it goes into the hot water tank showed there was not much heat.. Hmm, a quick look at the solar controller showed that it thought it was powering the pump, the light was on. The pump must have gone I thought, but these small pumps are very reliable. I wondered if the controller itself was to blame, so I turned it off and turned it on, then when the light came back on I could hear the relay 'click' and the pump started up. So the relay had stuck.

So thinking I might have fixed it, I left it a day and came back and had another look at it. Same thing, the light was on but no pumping going on. So this time I flicked my finger against the controller box and that was sufficient to make the relay set and conduct.

So the relay was 'shot' (very technical term). Now I got hold of the company through which I bought the system, they quoted me $125 for a replacement second hand controller or $250 for a new one. They also suggested (to their credit) that I could just replace the relay and see if that would sort it.

Wanting to avoid such expense I dismantled the controller and found the relay was a standard 12v coil with SPDT (Single Pole Double Throw) mains rated. In fact it was a rather low end relay operating at its make and break ratings (usually one has a relay with its make and break ratings well above the load, so it will last a long time). So I just unsoldered it and replaced it with a much higher rated relay from my 'stock' of electrical bits. Put the board back in and applied power and was rewarded with a nice strong 'click' and the pump was on and pumping.

Since this fix we have enjoyed again low cost hot water.

Whats the learn from this - if you find you are without hot water and the controller thinks it has the pump on, give the controller box a good flick - if it comes on, you have a bad relay which can be replaced for as little as $10..