Can anyone out there help us, pleeeeease!. A few weeks ago our hot water wasn’t hot anymore. When we checked the boiler, it had turned itself off. What happens now is, when it’s time for the hot water to come on, the boiler fires up and the pump starts. After a few minutes, the boiler cuts out but the pump carries on going until the timer turns the hot water system off again. The same applies for the central heating system. We’ve got an open vented system with 2 motorised valves for hot water and central heating. We thought it might have been the pump cos you could hear the boiler banging and crashing through the pipes before it cut out and there didn’t seem to be any water running through the system, just sitting in the boiler overheating. But after changing the pump, the boiler still cuts out after a couple of minutes, but minus the banging and crashing and the pump carries on running. Could it be the thermostat in the boiler causing the problem? The boiler is a Potterton Gloworm Spacesaver 50.

I think you will find that it is a Gloworm and not potterton, anyway first thing to check is that there is water in the header tank above the connection in the bottom, then try bleeding the highest rad..no water or air indicates a blocked cold feed. Lastly check to see if the motorised valves are opening when the boiler fires up, that will do for starters.

Mog

Thanks for your reply Mog :notworthy

There is definately water in the header tank covering the feed pipe. I've bled all the radiators upstairs and the pump itself until water comes out. I'm pretty sure the valves are opening as when they're on the little lever thingy has no effect and I can hear the valve closing when they turn off.

What do you reckon I should look at next? :confused:

Cheers,
James

Try measuring the flow pipe temperature with the boiler set on max, you should get about 82 deg C , what temp is the return pipe to the boiler when it cuts out ?.

Mog

Right, after changing the pump yesterday (for which I drained the whole the system due to the isolating valves being seized onto the pump), there must have still been some air somewhere. I've just being trying the C/H with the thermostat wacked up high to get all the rads hot. This seemed to move things around a bit and I managed to get a bit more air out of the rads. After this I tried the hot water again and (so far) it seems to be heating properly and turning the pump on/off with the tank thermostat now. I asume the boiler is behaving itself now as well - there must have been a load of air in the pipes near it or something.

Anyway, fingers crossed it's sorted now :thumb: