Ideal minimiser 70ff

[kb76]

Can anyone help with this. Fan runs, burner ignites for split second and goes out, wil continue to re-attempt without locking out. Have changed spark and detection electrodes and generator. Got 240v at the generator and manometer dropping couple of mbar when gas valve opening. Cleaned condense syphon and outlet appears clear, cleaned burner and inside heat exchanger as best I can. Am I missing something obvious? Thanks

 

[GrahamM]

These flues rot badly.
Check flue. Clean fan/lube clean venturies. Check APS etc. Check sensors.
All these good then maybe consider main board.

 

[Last Plumber]

Flame recognition. It could be the minimum BP ( start gas too low ) or the flame not carrying current. Have you checked that the boiler is correctly earthed ?
If electrode is new and positioned correctly, the gas pressure and flow is good, boiler is well earthed and voltages are correct it could be PCB.

Vital you check polarity.

If someone or something has reversed that then everything on the boiler can work except flame rectification !
Ask customer if anything has been altered recently or if you have altered or added anything, check that.

 

[kb76]

Thanks guys. Customer had a plumber in recently fitting new en suite and asked them to look at it too so assume it was playing up previously but will ask on Monday. Haven't check Earth on boiler or polarity at the terminal strip, will check these Monday also flue. Can I presume the APS and ventures are ok as the fan runs and there is ignition?

 

[Last Plumber]

I'd say if it gets to ignition and lights before going out, it's something following that so anything I previously said or indeed a flue problem ( good call graham m ), bad combustion would extinguish flame or effect flame recognition

 

[kb76]

Thanks. Can a possible bad earth be proved by simply carrying out a polarity test at the boilers main terminal strip? I also noticed the fan's o ring is in poor condition where it seals to the underside of burner which you mention could produce bad combustion. Are these available as a spare part without replacing complete fan?

 

[Billy Bob Bob]

other appliances in the house working ok?whats pressure at inlet when trying to light

 

[kb76]

They've not mentioned any other issues. 22mbar at gas valve before ignition and drops a couple but not completely which could point to regulator issue?

 

[Billy Bob Bob]

They've not mentioned any other issues. 22mbar at gas valve before ignition and drops a couple but not completely which could point to regulator issue?

yes but would drop very low TBH

 

[kb76]

Yep only drops 2mbar then back upto standing pressure. When had a faulty reg in past it practically dropped to a negative reading. No gas valve solenoid data in MI fault finding pages, could it possibly be a faulty gas section or blockage maybe? A few roads away new gas mains are being put in around town, I stripped it all back and checked the gauze etc but looked clean

 

[Billy Bob Bob]

Yep only drops 2mbar then back upto standing pressure. When had a faulty reg in past it practically dropped to a negative reading. No gas valve solenoid data in MI fault finding pages, could it possibly be a faulty gas section or blockage maybe? A few roads away new gas mains are being put in around town, I stripped it all back and checked the gauze etc but looked clean

wont be governor in that case ,could well be a blockage ,had it a few times

 

[jtsplumbing]

Check the Flue Stat ! think this can be reset !!

 

[Darren Jackson]

Thanks. Can a possible bad earth be proved by simply carrying out a polarity test at the boilers main terminal strip? I also noticed the fan's o ring is in poor condition where it seals to the underside of burner which you mention could produce bad combustion. Are these available as a spare part without replacing complete fan?

Thanks. Can a possible bad earth be proved by simply carrying out a polarity test at the boilers main terminal strip? I also noticed the fan's o ring is in poor condition where it seals to the underside of burner which you mention could produce bad combustion. Are these available as a spare part without replacing complete fan?

This test confirms the integrity (resistance) of the insulation between L and E on the boiler terminal strip. With the boiler isolated from the mains and switches, time switches and thermostats on and the multimeter set on ohms scale, Black lead firstly to E terminal and red lead secondly to L terminal. the resistance reading between L and E should read no other than O L ( infinity ) and if so, there is a faulty earth & a continuity check will trace the faulty component. This is separate to the polarity test.

 

[tamz]

Check the detection electrode and if thats ok sell her a new boiler. Probably the pcb.
What a heap of junk those were.

 

[kb76]

Thanks guys for your replies. Will carry out the electrical checks tomorrow when I'm back over there. The electrodes I've all changed and all stats I've also checked which I suppose now leaves flue, gas valve (blockage) bad earth or polarity etc

 

[kb76]

Update...checked polarity, earth and resistance readings all good. Chipped flue out and removed elbow all in good condition. When I shone a torch into top of heat ex there's a pair of bolts at the back on either side which I assume bolt heat ex sections together. Both were completely corroded and spread across the top of the heat ex. Poor combustion...who knows? New boiler going in! Thanks again for all your help