We had a new boiler fitted in the spring – a system boiler, not a combi, with a thermostat on the cylinder. It’s never quite worked properly. The symptoms are as follows:
The hot water (if we get any, see later) is always at the temperature that the boiler is set to. Since the installers left that at 85°C that meant we could make coffee with water out of the tap – we have turned it down to 65°.
Some days we don’t get any hot water at all, but if you put the immersion heater on it will start working again after a while
On the days we don’t get hot water, the controller and the app insist that the hot water is on, but the boiler doesn’t fire up
Yesterday was a no hot water day and I discovered that if I turned the thermostat down to a point below the actual temperature of the water, the boiler fired up.
This leads me to believe that the thermostat is wired so it only demands hot water if the water is already hotter than the temperature to which it is set. Is this possible?