Central Heating switching off before temperature reached

[Meerkat]

Hi - I wonder if you can help.

I have a Baxi Bermuda Inset2 Boiler - about 3.5 years old.

Over the past couple of weeks I've noticed that my Central Heating is switching off before reaching the required temperature. When I switch it on at the control panel the boiler fires up as normal, however, after it's been on for 5-10 mins the boiler switches off again - regardless of the temperature setting on my room thermostat. It then stays off for around 20 mins and then fires back up - but only for another minute or so! This cycle continues but it never reaches the point of getting my radiators much more that slightly warm.

I've replaced the room thermostat but it didn't help.

The hot water side of things appears to be fine - I don't have any problems heating this to the required temperature.

Any thoughts.

Thanks

 

[breezer]

i am not a plumber or heating engineer, but has some one (or mrs Feldman) turned the boiler stat down for the heating?

 

[Kristoflampie]

Sounds like a pump problem here....... boiler is reaching temperature and cutting out , cooling naturally over 20 mins and cutting back in but no heat is getting circulated to the radiators,hence only running for a minute after initial heat up, check the pump is running. Hot water is probably gravity circulated, no pump required.

Good luck........

 

[oilman]

If pump not running, sharp tap with hammer might help, or remove large screw from rear of pump, and use screwdriver to free the spindle. Water will dribble out so have a tray to catch it.

 

[Meerkat]

Thanks for the advice guys.

Checked pump and it appears to be functioning correctly. There's a definite spinning noise coming from it which gets slightly faster when I switch the pump setting to no.3. Also, I'm getting warm water through to the first couple of radiators within a minute or two of the boiler firing up - so it does seem to be circulating.

I removed the brass screw to check for sludge but it looked pretty clean.

The motorised valve appears to be switching on/off as required too.

I've turned the boiler control up to max but still no change!

Any other thoughts would be appreciated.

Thanks.

 

[breezer]

just a thought.

sludge / blockage?

 

[croydoncorgi]

'Spinning noise' coming from pump...
Oh dear. How loud? Pumps are supposed to be virtually silent. Spinning noises with no actual heat possibly means no water in pump. Since pump is water-lubricated, this is a Very Bad Thing. Even if there IS water in pump, this does not mean there's enough in the system to allow circulation. Check for air in highest rad in system (with heating switched OFF). If air comes out, carry on bleeding until water appears, then bleed rest of rads. If nothing comes out, check there's water in F&E tank (the little one!) which supplies central heating. After fixing that, bleed rads.

 

[namsag]

When you have the boiler on for just CH only, and after it has fired up then turned itself off check that the motorised valve is still open as sometimes the motor overheats and closes the valve then comes back on after it has cooled down just the same as your symptons .

 

[Meerkat]

Croydoncorgi - apologies, I probably made it sound louder than it was - I was actually listening very carefully to hear the spinning sound - it was virtually quiet but spinning was the the way I would describe the sound. I've tried bleeding the rads and I'm getting water instantly from all of them.

Namsag - the valve is closing when the boiler switches off so I've got a replacement synchron motor - I'll replace this and give it a try. Fingers crossed.

Thanks for your help guys.

 

[ChrisR]

Have had a run of pumps making the right noises but having their impeller slots full of gunge so doing practically nothing.

It should be a simple matter to turn off the pump valves, remove the 2 or 4 allen screws and take off the head of the pump to have a look. "Should" - ha ha. Worth a try though.

 

[Meerkat]

Thanks again for your helps guys.

Changed the motor on the valve and all now appears to be back to normal. Special thanks to namsag for pinpointing the problem.

Cheers,
Meerkat