I know very little about plumbing, and am looking for some advice on diagnosing a problem.
We have what I suspect is a fairly average heating system. A Potterton Neataheat boiler and controller box downstairs in the kitchen and a hot water storage tank upstairs in the bathroom. The pump is next to the tank and feeds into the tank and radiator system via a couple of motorised three-way valves.
A few of days ago we stopped getting hot water through the taps. Here's what I've obsrved:
- If we turn on only the heating then the boiler fires up, the pump starts, and the radiators heat-up. - If we turn on the heating and hot water then the boiler and pump star and the storage tank fills with hot water. The 'lever' on the back of the motor controlling the heating valve moves, so I think we get hot water in this case because the heating-circuit valve is opening on command and the pump is moving hot water through both valves. - If we turn on only the hot water then the valve motor appears to open the heating circuit valve, but the pump does not activate. Neither does the boiler.
I'm hoping for some advice on what could be causing this. The valves, pump, and boiler appear to be okay. I suspect that the thermostat on the hot water tank is faulty, and the pump and boiler aren't starting because the system thinks that the tank is full of hot. Thats just a guess, though, because I don't know much...
I'd be grateful if anyone can suggest things I should check to solve this. In particular, how to test the tank thermostat. I'm fairly proficient with electrics, and can get access to a test meter if necessary.