Help, combi boiler switching on and off very frequently when hot

[PeterF2]

Hello

I've got a Worcester 28Si combi boiler, it's quite old now (8 years?) but has been running well with no problems since new. Because it's in my elderly mum's house the heating gets used quite a lot and is set fairly high (20 degC)

Switching the heating on from cold the boiler will fire up OK and runs fine. It's controlled from a room stat which is working OK.

Previously it would switch off occasionally and then fire up again a few minutes later, even if the room stat was on, I guess this is normal?
More recently however when it's been running for quite some time it will switch off then switch back on and then off and then on and continues like this every few seconds.

The system pressure seems ok, about 1.5 bar, the radiators are hot with no cold spots.
The only other symptom is that the radiators and hot water seem much hotter than previously. The temperature control dials for the radiators and the hot water don't seem to do much.

Any ideas about this problem? Is it likely to be something simple like a sensor? I'm not a plumber but would appreciate any advice before I call a plumber who tells me I need a new boiler!

Thanks

Peter

 

[Rickster123]

When was the boiler last serviced?

 

[PeterF2]

It was checked by BG in February. It passed all the function tests but they don't clean the burner etc. He measured a pressure in the boiler, checked temps and flue.

 

[IDCHAPPY]

When was the boiler last serviced?

:lol:
In the factory?
It sounds like it's cycling, boilers don't run forever on the heating cycle, once they get up to temperature they shut off for a few mintues to allow the water to cool then start again.

 

[IDCHAPPY]

P.s, you in no way need a new boiler mate, get it serviced and the system checked if it's bothering you but it soundslike it's working perfectly normally to me :wink_smile:

 

[PeterF2]

:lol:
In the factory?
It sounds like it's cycling, boilers don't run forever on the heating cycle, once they get up to temperature they shut off for a few mintues to allow the water to cool then start again.

I understand it will cycle, but the cycle time has gone down from a few minutes to 5 seconds! :shocked3:

It's been serviced every year since new but BG just seem to check pressures, temperatures and flue gas.

 

[AWheating]

I take it it's never been serviced?

Find a local engineer and get it serviced and tell the engineer of the issues before he/ she starts. Might also be a good idea to get the heating system water checked for corrosion and inhibited. Maybe even a good flush will be needed?