Vaillant VC GB 242 EH Boiler

[SCAman]

Hi, the above boiler has been in use for 15 years.

Very intermittently over the last two years the flame failure device has activated on timed start-up, but has reset fine. My local engineer could not identify any apparent cause at each of the two last annual services.

In the last 3 months the instances of flame failure have increased to the point now where, instead of activating perhaps once a week, it probably fails on 90% of the 3 per day timed starts. And, instead of completing the the programme cycle first time, progressively in the last month the required no.of resets has increased to anything from 3-15 (even if I try waiting 5 secs before trying a re-start) before the boiler activates continuously and lets the programme complete its cycle.

An alternative plumber tried replacing the Flowshare valve last week - for the first few times we got back to a single re-set but now we're back in double figures and I'm getting a sore finger - to say nothing of sore ears from the wife and kids!!

Any thoughts/suggestions of other areas we might try please guys - before I have to resort to the expensive one of getting a completely new boiler?

Thanks.

 

[Rob]

Is the boiler actually alight when the flame failure occurs or does the gas valve not open?

I had a 142 today which would light but kept sparking. The ht lead just needed a good cleaning.

If it doesnt get as far as lighting then suspect pressure diff.

 

[DP]

What is a flowshare valve. Fail to see how an external motorised valve can influence the flame detection circuit.

Does the boiler malfunction during HW demand as well?

 

[z900iain]

I have had a similar problem with my own Vaillant 242. I changed the flame sensing electrode which improved the boiler but after a week or two it then started playing up again though not as bad. I then changed the flame supervision board (one of four boards in the silver box on the left hand side ) this made it a lot better. I also cleaned the sensing wire as i have heard this can help in sensing the flame . The boiler now runs ok , just throws the occasional wobbly waiting for it to run hot water (running hot water can take as long as 30 second before the boiler fires up) hope this is of some help

 

[ChrisR]

An alternative plumber ...

Did he use acupuncture or aromatherapy on it?

 

[SCAman]

Thanks for all your contributions.

Answers to the queries as follows:

Rob884: Oh yes, it lights okay, runs for varying intervals 5 - 15 secs then cuts out. Eventually seems to stay in once you can hear the water starting to pump to the cistern - I'm presuming the pump is thermostatically controlled so water doesn't start circulating until it's heated to somewhere near temperature.

DP: Flowshare diverts supply to either HW, CH or split. There was a questionmark over whether it was still functioning correctly - again 15 years old - so replacement was an easy elimination step. Failure happens whether HW, CH or both. Also tried tried adjusting boiler operating control through setting ranges 2-6. No improvement.

z900iain: Thank you. Your flame supervision board sounds a promising next step.

ChrisR: by the time I've finished we'll have probably used kiss of life, CPR, and resus paddles - to my wallet as well as the boiler!!

Thanks for all the posts - all contributions - even humorous are much appreciated.

NB I'm in Crete for 10 days from tomorrow (understand HW shouldn't be a problem, but leccy?) so intervening lack of response to any further posts will not be rudeness/ignorance/ingratitude.

Regards

 

[Agile]

Could it be dampness or condensation first think in the morning?

Can you match the malfunction to weather conditions?

Tony

 

[SCAman]

Hi Tony.

Unfortunately not - and we have had some occasional warm dry days since Easter!!

Same failure whether auto or manual starts 0600, 1200, 1600, 2000.

Thanks for the thought.

 

[z900iain]

Hello
Hope you had a good holiday . i was just reading your last quote on this subject . have you tried venting the boiler from the auto air vent . just undo the cap maybe 2 turns and you should hear any air coming out , then close the cap. on mine it is located on the very top right hand side . when i did this to my boiler the pump really quietend down. Iain

 

[DP]

Boiler is a combination boiler.

Flowshare or (another format of same) midposition/ diverter valve would only be fitted if the installation is spilt i.e. between say bedrooms and living rooms. This valve may well be a leftover from previous.

Auto air vents are supposed to be 'left open' to allow air to escape as need be.

A lockout such as what the OP is encountering can only be cured by looking into what is root cause is. Another way fix it is by changing all the parts that comprise ignition sequence.

Why does your engineer or you start the boiler in the morning and see if the spark is present, gas is available at the burner, flame is detected and spark removed.

A few months ago I came across a boiler that was failing for similar reasons. Examination of burners revealed airborn debris stuck in the burner bar. All the ignition components could have been replaced on this boiler without effecting a cure. So, my advise is look for the defect, do not assume anything (especially do not start changing PCBs on a whim) and get the boiler serviced (not a 10 minute visual operational check- but a proper service as detailed in the manual) which often works wonders as system components move and operate in a precise manner without inducing lags as another poster has encountered.

 

[SCAman]

Thanks guys - excellent holiday. Tried powering boiler off for 10 days that away, but more for safety than a vain hope.

Fired up okay after several resets but 3 days on and it's taking ever more resets.

However, now just found another potential symptom/indicator when I opened top door and watched flame profile. After reset and a few seconds main burner starts and runs on low flame (@3-4mm). However, the moment additional gas starts to flow and the flame increases (@6-8mm), cut-out trips.

NB Tried various season settings 2-7 to force issue. Don't know if it suggests anything but less than 3.5 main burner doesn't seem to ignite at all even with water circulating. 4-7 and I'm getting as previous ie after reset and a few seconds main burner starts and runs on low flame (@3-4mm). However, the moment additional gas starts to flow and the flame increases (@6-8mm), cut-out trips.

Do these symptoms point to a more particular component issue please?

Regards.

 

[Agile]

Obviously the gas valve setting should be checked ( CORGI ! )

My expectation is that the APS is dropping out with an increased flame size.

Fan/venturi/APS

Tony

 

[SCAman]

Not looking promising.

Air Pressure Switch changed, flame sensing electrode and lead checked - no change.

Last throw of dice = Flame Supervision Control Board and Vaillant engineer - as long as total charges is not prohibitive. Boiler has done 15 years after all so, even if we get it working, pump could go next (nothing's ever needed replacement before).

Local parts supplier advised that course as "with no. of differend specs they have apparently had to order in as many as 14 boards to get right one in past" - ie hopefully Vaillant will carry right one on van.

 

[Agile]

Merely changing parts is not the quickest and cheapest way to repair a boiler.

It seems that the important CORGI aspects, the gas valve settings and venturi have not been checked.

I am not up to date with the latest vaillant engineer charges. They used to be about £94 plus parts but thats a long time ago and they may have gone down the road of the others charging about £200 on a fixed price basis.

A competent independent is likely to be cheaper than a Vaillant engineer.

Tony

 

[SCAman]

Thanks Tony,

Now tried two local Corgi reg engineers and neither have been able to identify or resolve.

I agree with you - local should be cheaper but, short of the recommendations I've already tried, I think I now have little choice but to bite the Vaillant bullet.