gas combi-boiler doesnt like cold weather!

[scotster]

I have a combi gas bolier (worcester 24cdi) which keeps cutting out when supplying hot water or heating.

It runs for about a minute or so then there is a slight clunk and it cuts out. I have to reset it using the little red button.
I repeat that about eight times. Then it runs fine.....

Water presssure is fine at 1.5 bar and it occurs for both hot water and heating.

I figure it must be temperature related as once its been running a while its fine and it only happens in winter, never in summer. And if I leave the heating on all night in winter it works without fault.

It has started to get worse though and unless the room temp is high when the weather is very good it is happenning more and more...

A friend a work who knows a bit about these things said it sounds like the solenoid could be getting tight.

I want to have a vague idea b4 I get in an engineer who I wont trust not to fleece me.

I assume as Im not corgi registered I cant 'have a go myself'

Any thoughts welcome.

 

[COG]

If your pressing the red button to re start the you must have either a slow flashing CH light or both CH and DHW flashing slow at the same time if its both then its an overheating fault if its only the CH then its a flame failure fault . so one light or two flashing ? ?

 

[scotster]

One light flashing. The radiator one.

The flame red indicator light cuts before that starts. So it is the main burner dropping out. You can hear the burner switch off.

 

[COG]

That light means you have burner lockout ,the faults are , flame senser faulty, min gas pressure too low or pcb fault . as it wil eventually light its usually min gas pressure too low . its easy to re set with a manometer if you have someone qualified to use it that is. What type of gas valve is fitted to your boiler?does it have the plug in leads at the front or the back?
The junkers gas valve is the easiest to adjust (plugs at the back).

 

[scotster]

Ill check it out on Monday COG. Im away for the weekend.

Why would low pressure be temperature related though? It runs fine during the summer when the ambient temp is high.

Thanks for your help so far.

 

[Agile]

When a function is "on the edge" of working or failing even very small temperature variations can have the effect of making it work or not work!

Tony Glazier

 

[scotster]

Cheers Tony. I understand that.

I guess my real question is:

'What is most likely to be the failure point based on it being temperature sensitive'

Also take into account that after the fourth or fifth button press it runs OK so whatever needs 'warming up' is warming pretty quickly.

This makes me think that it is unlikely to be the PCB as I imagine that the PCB is kept well away from anything getting warm....

A further clue is that the burn has recently started sounding uneven and louder than normal.

 

[scotster]

wd

 

[Agile]

It has already been suggested that the problem is likely to be the setting of the gas valve.

Exactly what is causing the temperature variation is totally irrelevant. The combustion chamber warms from 20 C up to about 400 C for example.

As you have been told that its probably the gas valve setting why dont you accept that as the most likely without fixating on the PCB or any other components ?

Tony