"Andy Johnson" wrote in message
ups.com...
Hi,

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.

Thanks, Andy


Forget the tank thermostat - if the motor in the valve is energised then it
must have a supply to it. the most likely fault is the microswitch in the
valve head has failed or the conductor (usually orange and grey wires) from
it to the terminals in the junction box are open circuit. (what make of
motorised valve do you have?)