Oil fired central heating problem. Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Raynwb]

Hi,
I have a wall mounted central heating boiler (oil fired) that was fitted just over two years ago. Just lately it has not been shutting down.
What is happening is when the system should be off on the timer she still fires occasionally. i have had the engineers in and they say the boiler is fine and that the motoriised valve is at fault. This has been replaced and still the problem exsists.
Could either the room or cylinder thermostat be at fault and still calling for power. The hot water gets very hot and when only the water is on the radiators get warm. They work normally when set to heating. The system is a fully pumped system that has not given me any trouble until now.
Would be very greatful you can cast any light on the problem.
Ray

[sparx]

Hi ray, don't know how far your electrical ability takes you but will assume u r ok for some basic checks to see if fault is with boiler or controls. you will need a basic voltage tester (2 wire NOT neon screwdriver).
At boiler there should be a Neutral, earth, permanent live, & a switched live from control circuit, test between N & Perm. L, should show mains voltage always, test from N to sw. Live, should only have mains voltage when controls 'calling' for heat, either C.H.or H.W.
this is check to do when you think system should be off but boiler ON,
if this is live at wrong time then controls fault, if not live but boiler ON , then boiler PCB fault!
From your description I would check tank stat, is it firmly held in place on side of cylinder, are connections good, check these first, then repost & will try next steps, regards SPARX

[Raynwb]

Thanks Sparx, will get back as soon as I have completed the tasks.
many thanks
Ray