WB Greenstar Intermittent lockout issue

[mitchino]

We have an outdoor Worcester Bosch Greenstar 25/32 Oil Fired Combi.

We are getting a random lockout fault, code 855 9F. Pushing reset sorts it for a while sometimes an hour sometimes 4 hours.

I can't get hold of the engineer that installed it. Is there anything I could try until he responds?

I have already tried to bleed air from the oil inlet, there wasn't any air, and I have checked the photocell, it's totally clean.

Any other suggestions?

 

[SimonG]

Ignition fault. Lack of oil, wrongly positioned electrodes, etc etc
Absolute dog **** boiler.

 

[mitchino]

Is it? What is a good exterior oil combi?

 

[SimonG]

No such thing.

I would have an exterior heat only Hounsfield and an unvented cylinder.

 

[mitchino]

So it’s definitely more reliable when the hot water is switched off and it’s only dealing with the heating. Does that give any clues to what the problem is?