Worcester 30si Ignition Lockout

[Aquazone]

Call out on way home from work from a new customer with Worcester 30si combi. She has had no central heating for approx 5 weeks. Hot water works fine.

When there is a demand from the room stat, the boiler starts up (fan etc) burner lights, then goes out after approx 5 seconds. Fan slows down then has another go. 5 attempts and goes to ignition lockout.
The weird thing is that the CH works properly at max when you put it into service mode.

A previous engineer has replaced the diverter valve head and the PCB, and when new PCB didn't solve problem she wasn't happy and wanted second opinion.

Any ideas? Said I will call round there tomorrow AM to test, but wondering if anyone else has had this problem?
When I called round she had MI's and the pattern of the flashing blue light confirmed it was ignition lockout fault, not overheat.
Will obviously need to eliminate usual suspects first (gas valve, flame supervision etc) but all works in HW mode and service mode.......

She also said HW is only just warm since he installed new PCB, and had been piping before, but that may be a separate issue.

 

[Millsy 82]

Check the condense traps not blocked.

Does it work on low flame? It could be set up all wrong and the CO2% too high/low and the flame is going out or starving itself of oxygen.

I would start by checking that or failing that I would give it a full strip and swap the ignition/ flame sensing probes as well as the red gasket at the top.

The gas valve on these is either open or closed so I wouldnt of thought it would be that.

 

[Aquazone]

I was going to start with a service to check CO2% etc, clean trap and do working pressure and gas rate for a start.

But I suspect these will turn out to be decent as it works on HW mode, or has done properly for 5/6 weeks. Only today after having PCB replaced she said water is only slightly hot, which it was when I tested it.

On paperwork previous engineer left, said gas rate was low and at 15kw when it should be at 25 approx. not checked these values for accuracy though.

i can see a call to WB tech tomorrow coming on.

Thanks Millsy

 

[Millsy 82]

When the boiler runs on hot water generally it will be running flat out to heat up the water in such a short space of time when it runs on heating it will not be running at full pelt and this is why I suspect that it will need setting up properley before you start. So after you set the high up turn the heating knob right down and see what you get.

He might not of done the gas rate correctly or noted it down wrong. I always do my own checks I dont trust half the people I know to do a good job let alone a stranger.

Worcester tech are really helpful though but the CO2 will be the first thing they say I will guarentee it.

 

[Aquazone]

Yeah I'm gonna FGA and do a full service, as like you I don't trust whats been done before, and especially if its taken 6 weeks to fit a (unneeded) diverter valve and PCB!!

Will update the thread with what the problem is, and (hopefully) a fix.

 

[moogwai]

I had this the other week after I had replaced the flow manifold....wierdly all I did to solve the problem was check the fan harness for continuity and check the overheat stat and harness....when I put the connections back on it started straight away!! Dont know whether the connections had a bit of muck on or what!
Maybe I was just lucky on this occaision.

 

[mfgs]

Sounds like it needs a full strip and clean. Check the negative fan pressure.

 

[Aquazone]

Went back this morning, got good Co2 on max, but on minimum just kept lighting for 5secs or so then going out, so couldn't get any minimum readings. Found this problem started straight after a service by the other engineer.

Condense trap clear, neg fan pressure good, gas valve coils good as well as harness, and WP at 21 mbar.

Rang WB tech line, and the problems with these symptoms are either too low WP, bad neg fan pressure or bad CO2 readings.
They advised a factory reset on gas valve (Sit Sigma 848) which for the 30SI is both min / max screws all way shut, then turn max 7 & 3/4 turns open and min 2 & 1/2 open. This solved the problem, and then set it up correctly with FGA as it stayed lit.

Guy at WB says this is quite common as the minimum screw is the biggest one, and max is the smallest, and people get it mixed up?

Anyway thanks for input, and hope this can help someone else in the future

 

[vern]

Went back this morning, got good Co2 on max, but on minimum just kept lighting for 5secs or so then going out, so couldn't get any minimum readings. Found this problem started straight after a service by the other engineer.

Condense trap clear, neg fan pressure good, gas valve coils good as well as harness, and WP at 21 mbar.

Rang WB tech line, and the problems with these symptoms are either too low WP, bad neg fan pressure or bad CO2 readings.
They advised a factory reset on gas valve (Sit Sigma 848) which for the 30SI is both min / max screws all way shut, then turn max 7 & 3/4 turns open and min 2 & 1/2 open. This solved the problem, and then set it up correctly with FGA as it stayed lit.

Guy at WB says this is quite common as the minimum screw is the biggest one, and max is the smallest, and people get it mixed up?

Anyway thanks for input, and hope this can help someone else in the future

lol just seen this had it a few times, customer had it serviced it was working , wrongly adjusted, after many parts he quoted her a new boiler, I had fitted next doors, so popped round all sorted in 30 mins.

 

[Millsy 82]

Thats the good thing about worcester speak to the tech line and they tell you how to reset the gas valve. I had a vaillant and somebody had messed with the gas valve the red gunk had gone off it so I knew straight away spoke to vaillant and they just said new gas valve required.

Its great following people like that around though it always gives you more work. Why didnt he realise he'd messed up surely when he made an adjustment and nothing happened he stopped.

 

[bewsh]

I'm sure when the boiler is in maximum mode, it cancels out the flow thermistor. So could be worth checking the resistance coming from that under normal operation?

 

[Nostrum]

It's fixed....

Lost count how many times I've had this fault caused by the previous engineer not having a clue.

 

[bewsh]

Ye same here, I'm sure it even says in the MI's to check the CO2 values for this fault. People forget the basics sometimes though and over-think it.

 

[ambrosia]

Lost count how many times I've had this fault caused by the previous engineer not having a clue.

you really need to stop following me about