Boiler starts working only for 1-2 mins

[Linds99]

A few months ago my heating would only work if the water was switched on at same time. A few days ago I switched them both on and radiators were not getting warm. I bled all of them, checked the lockshields and trv's. all of them ok. i left the main switch to boiler off for about an hour. When I switched it on and reset, water and heating comes on but only for seconds to 3 mins. It does stay on for longer throughout the day but I have to keep on all day because if I switch it off it will take ages to come on or not come back on at all. We have hot water, so when the boiler is switching on it must only be heating up the water...then eventually the radiators.
My boiler is about 18-20 years old it's a suprima boiler. I have water tank in loft and have eight radiators in total up and downstairs. I have two young children, so would like advice to fix. Hope you can help

 

[45yearsagasman]

Pump, motorised valve, or some sort of restriction would all cause the symptoms you describe. It does depend on how capable you are to undertake finding and repairing the fault, and if you have the tools to do so. It may be that in your case a local heating engineer would sort you out a lot easier than starting a long DIY attempt. I don't think your boiler is as old as you suggest.

 

[Linds99]

Pump, motorised valve, or some sort of restriction would all cause the symptoms you describe. It does depend on how capable you are to undertake finding and repairing the fault, and if you have the tools to do so. It may be that in your case a local heating engineer would sort you out a lot easier than starting a long DIY attempt. I don't think your boiler is as old as you suggest.

I turned my water and heating on this morning at 6.50, only about 15 mins ago the radiators upstairs have come on, but not downstairs. I have turned the thermostats down on all 4 upstairs, which has forced 2 out of 4 radiators to come on downstairs but only Luke warm. Thanks for reply

 

[45yearsagasman]

That could be a circulation problem, either pump or blockage. Only way is to start having a look inside. There is little you can do without going down that route.

 

[converse]

Same thing happened to us recently, we thought it was the pump, turned out to be a solid blockage in the feed pipe from the expansion tank in the loft, virtually no water was getting in/around, so the boiler temp was reached in seconds and nothing ever got hot. Plumber found blockage using a magnet, cut out a metre of so of pipe in the a/c and sorted it all. Very impressive, never thought that could happen (I'm not a plumber!).

Started the same as yours, few rads didn't get hot, then more, then none downstairs, then hot water failed, then only one radiator worked at all. (Did exactly the same as you when it was first failing, turning off radiators to force others to come warm.)

 

[Agile]

These kind of faults are fairly easy to diagnose but require many different aspects to all be considered together and thats often easier for a professional.

Tony