worcester 240 tripping on and off

[tasmanian]

hi.
i have a worcester 240 combi. when on heating mode it runs 4 20 seconds or so then trips off 4 20..then repeats the cycle cont.

i can hear the clicking sound coming from the circuit board.

jus before it goes of it makes a sound as tho pressure is building up somewhere within

also when we run the hot water for a while it seems to drop temp on the radiators..nt sure if this maybe linked

water pressure is fine at 1.5/2.0

any help would be much appreciated

thanks
tas

[toscal]

What is the rad temp set to on the boiler. If this is too low then it may cause this on off pattern. Try setting it higher say about 3 or 4. Also if it is too low and you then run the hot water you will notice that the rad temp will drop as the Hot water takes priority.

[tasmanian]

thanks toscal

rad temps are set at 4/5. disconnected room stat and wired direct just 2 be sure already but no change. rads only warm up slightly due to on off scenario.

really feel it may have something 2 do with the suspected pressure build up noise it makes which is when it switches off.

wonder if there may be a blockage within exchanger or something of the sort..wat u think?

[neilhooper]

Totally agree with Toscal. However have you considered the age or your boiler, specifically the pump. How many radiators have you got? The pump could be getting a bit weak and not pumping the water around the system very quickly ie warming the radiator water up hitting the thermostat level and cutting off, then water moves on a bit and the whole cycle starts again. Have you noticed if it does the same when the radiators are cold when the heating first comes on ?

There are a few other things that it could be but more information is required.

Regards,

Neil

[chris_j_hunter]

another thought is the flue - is it blocked ... we had a bird nest in ours once, boiler ran (apparently) for a short while, then died, everytime ... the boiler always ran the fan for a while before firing up, to purge itself of any risudual gas, the back-pressure sensor in the flue sensed the obstruction, and cancelled the fire-up ...

if not that, maybe some other safety device ?

[neilhooper]

another thought is the flue - is it blocked ... we had a bird nest in ours once, boiler ran (apparently) for a short while, then died, everytime ... the boiler always ran the fan for a while before firing up, to purge itself of any risudual gas, the back-pressure sensor in the flue sensed the obstruction, and cancelled the fire-up ...

if not that, maybe some other safety device ?

I don't think that this model has an actual back pressure sensor.

As I said earlier more information may be required to sort this out if it hasn't already by turning up the boiler thermostat.

- Neil

[toscal]

One way to see if there is a blockage would be to disconnect the boiler and pour water into one end of the heat exchanger and see if it comes out the other. Probably not the easiest of solutions. I know our combi boiler (which is also a Bosch) would be a real pain to disconnect and do.
What type of room stat do you have. I know you have disconnected it, but do you know if its a low voltage type or just a simple on off switch.
Does your pump have a small switch on the underside. Maybe try and switch this to the other position, there is normally only 2 positions. All it does is change the speed of the pump.
If that doesn't work then it maybe worth getting an engineer in to have a look and check the boiler and heating system.