Hi.
We have had a Siddons heatpump system for years, and have been excellent. 320L with a separate compressor system.
Derwent T2A and temp set is at 57C
In the last year or so, the thermistor on the water tank has been failing. We call in the local hot water guy and he checks the system, resets the button on the compressor and it runs ok until the thermostat over heats the water and the button pops off again. Removing the thermostat, the package is loose and the top can be moved around the base. A new thermostat is solid and it works 100% until the cap gets loose in weeks or months and the problem returns. The cap is connected to the base with 4 clips, not welded or significant crimp.
Asked Derwent if I could buy a box of them so I can fix the issue easily, and yes I can buy them but the price is $75 each plus GST and freight. It's just a bimetal temp gadget with no electronics, poor manufacturing and outrageous pricing!
So now looking at options. We know the compressor is working 100%. The tank heats fine but the thermostat is the failing problem. Looking for an alternative, found a Temp controller with a temp sensor and a 240v relay and an adjustable temp: https://www.ebay.com.au/itm/281280638271
Have ordered one of these to test. The controller has a 10A 240v relay, and I hope it is adequate but given the Derwent is a failure I expect that is a minor issue. If it has an issue, I could add a 15A relay.
Any suggestions or options I should be looking at other than replacing the whole system because of a silly thermistor?