Gas Boiler Problem

[ferryman]

Can anyone help me with this please. Combi gas boiler in heating mode is coming on for a short while then switching off in quick succession, I timed it yesterday with room stat on 18 it was two minutes on, two mins off. Never used to do this. later on after putting room stat up to 20 came on for ages all rads very hot and when it had its off period it was for about 1 minute then on for a long time on again and room was very warm.

I then turned room stat down to 17 and room got very cold and the boiler didn't come on again we had to manually turn room stat up. Sometimes at any setting of room stat it doesn't maintain constant rad heat at any temperate which I think it should do but I don't know much about this sort of stuff.

When listening to boiler where it's situated and boiler on, the boiler stat itself isn't always switching on and off (you can usually hear it) but the boiler dies down to go off then a minute or so later the heat comes on again.

It has just had it's annual gas safety check (which the landlord has done every year for many years now) however the boiler hasn't had a full service since the safety checks started! So it's not had a clean out for many years so do you think this has created the problem it's having now? Sorry for long post, don't no how to put it otherwise. Cheers for any advice.

[CrapAtCryptics]

Have you topped up the water level, there should be or or two taps and a dial that shows the level - keeping it in the middle is usually best. If you still have the manual or can find it online there will be more type specific help.

[ferryman]

thanks cryptic. I wouldn't really like to touch anything because it's not my property and don't want to mess with the boiler specially. so can't be sure about water levels and also why would that affect boiler switching on and off do you know.

[Garaman]

The stat only gives an on/off command to the boiler, so if the boiler didn't come on at 17 but did when you turned it up, that doesn't indicate a problem with the boiler. Similarly if you the boiler doesn't go off automatically but does when you turn the thermostat lower that doesn't indicate a problem with the boiler. They both are just indicating that the thermostat isn't working as it should, or the room isn't the temperature you think.

[ferryman]

Cheers Garaman, I realise all you say is correct but what it doesn't answer is firstly why when it has never done it before, does it switch on as I timed it at two mins on and two mins off at ANY temperature and without touching the room stat it sometimes goes off altogether, the room gets cold and boiler doesn't come on unless I manually turn the room stat on OR sometimes the room gets cold and it does come on again half an hour later with the rads not maintaining their heat.

This has never happened before and that's why I am wondering if because boilers not had a proper service in years could that have caused this present situation because of them only doing a safety check. This current problem only occurred since they did the safety check last week. Thanks for you reply.

[Garaman]

It isn't easy to understand exactly what is happening from what you describe, ferryman. You write //the room gets cold and boiler doesn't come on unless I manually turn the room stat on// Well if the stat was doing its job it would already be on, and if it was on, turning it on wouldn't have any further effect, so it clearly wasn't on.

The stat is only completing a loop from your boiler, either its open circuit or its closed circuit.