Worcester Combi 240 won't turn off

[pg325]

Recently I've noticed that when I turn the hot tap off the boiler will either continue running or the boiler comes back on shortly after, it fires up and you can hear the pump running even if I switch the boiler to off, the only way to stop it is to turn off at the spur.

The Honeywell digital stat does not show a flame indicating its running and is set to manual at a very low heat to stop the boiler working.

Any ideas what would cause this?

 

[macfudd]

Are you absolutely sure the burner is firing up?
After running the hot water,the pump in a combi will often come on for a period to dissipate the heat build up in the boiler.

 

[pg325]

Are you absolutely sure the burner is firing up?
After running the hot water,the pump in a combi will often come on for a period to dissipate the heat build up in the boiler.

Yeah its firing up and burning, I've taken the front cover off and you can clearly see a nice bright blue furness!

 

[pg325]

Bit of an update, I had the heating on for a couple of hours last night, since then the boiler and pump have not come back on, this is how its been going for the last couple of weeks, all ok then all of a sudden constant firing and pump running.

I also noticed the pressure went up to near 3 bar when the heating was on, thats been an issue for a long time, I think the pressure valve membrane is perished, could the 2 be linked?

Any ideas?

 

[bengasman]

I also noticed the pressure went up to near 3 bar when the heating was on, thats been an issue for a long time, I think the pressure valve membrane is perished, could the 2 be linked?

Any ideas?

I got the idea your boiler has not been serviced for a long time.

 

[picasso]

do you have a frost stat fitted ? failing that it might be a sticking relay on the board.

 

[pg325]

do you have a frost stat fitted ? failing that it might be a sticking relay on the board.

There is a frost setting on the Honeywell digistat but that should only kick in at a very low temp. Could be a new board then?

 

[picasso]

cant tell without being in front of it , could also be a sticking divertor valve micro switch, dont waste your money by throwing parts at it, get an rgi to have a look.

 

[pg325]

cant tell without being in front of it , could also be a sticking divertor valve micro switch, dont waste your money by throwing parts at it, get an rgi to have a look.

I can hear the switch clicking when opening the hot tap and closing.