Oil Boiler Not Working

NatureGirl

I have an oil fired central heating boiler that worked brilliantly all during the cold spell in December. The water in the house didn't freeze at all as it was all kept nice and warm...

The problem came when on Stephen's Day the radiators were suddenly cold.

I checked the boiler and what is happening is this -
When you switch it on it starts working as normal. But the radiators stay cold. The water in the boiler soon reaches the temperature set on the thermostat and so the boiler cuts out. The hot water appears to not be leaving the boiler.

I had an electrician check the electrics on the boiler and all is OK.

I then learnt how to check the pumps with the screwdriver trick (there are 2, 1 on either side of the boiler). Both pumps turn easily and smoothly.

Could there still be a problem with a pump ? Could it possibly be caused by an airlock (and why) ? Is there anything else it could be that I haven't thought of ?

I can't afford to call out a plumber/central heating engineer at the moment (electrician was a friend), so am hoping to try and fix the thing myself as I'm sick of being cold and chopping wood from the copse after 7 weeks of no central heating :eek: !!!

Many thanks in anticipation of your replies

NatureGirl

I should have said my fiancee chops the wood...

Buford T Justice

Have you an open or sealed system?
If Sealed, what is the pressure of the system?
If open, is there water in the header tank?

Why have you two circulating pumps on the boiler?

Have you any motorized valves on the system (possibly hot press) that could have failed and are now stuck in the closed position?

More info needed.

NatureGirl

Many thanks for your reply Fingers.

Have you an open or sealed system?
I am not certain. However I can let water into the system via a manual valve which is in my laundry room, very close to the system's pressure dial.

If Sealed, what is the pressure of the system?
When working correctly the pressure is just under 1 bar.

If open, is there water in the header tank?
I searched for a header tank in the many attic spaces as well as in every other space I could find... no header tank.

Why have you two circulating pumps on the boiler?
I have no idea! I was hoping that someone on here could tell me that...

Have you any motorized valves on the system (possibly hot press) that could have failed and are now stuck in the closed position?
I'm afraid that I don't know what a motorised valve looks like or where on the system I might find one.
I have no hot press. The hot water immersion is in one of the more obscure and hard to reach attic spaces (the smallest one) :eek:

I hope I don't appear too useless !!!
Many thanks

tonysea

Hi,

Do you have a "hot summer valve" on the system that isolates the rads? If so check it's open.

Are your radiators controlled by a roomstat? has this been turned down without you knowing?

Is the boiler heating the water in your cylinder?

NatureGirl

Hi Tony

Do you have a "hot summer valve" on the system that isolates the rads? If so check it's open.
I'm not aware that I have a 'hot summer valve' on the system.

Are your radiators controlled by a roomstat? has this been turned down without you knowing?
No, there is no 'in house' theremostat/roomstat. Nor are there stats on the radiators.
The only thermostat I have found is on the boiler to control the actual water temperature in the system.
My only means of controlling the system is via a time clock in the laundry room (which I have made sure is in the correct position to run the system)

Is the boiler heating the water in your cylinder?
Nope It was normally very efficient.

PS
I have also obviously tried restarting the system with the start button on the boiler, as well as the timeclock. The same thing happens - it runs but no hot water circulates, and then the thermostat on the water in the boiler kicks in and the whole system shuts down.

There is no air in the system between the oil tank and the boiler as I have checked that via the bleed nut.

tonysea

H,mm, I know you said the pumps are freely turning but can you feel/hear them running when you switch on the boiler? although the water should actually circulate by convection without the pumps. It sounds like a closed valve somewhere to me.