Wolf CGB Boiler No spark

[JUpton]

Hi, I am trying to find out some information to help me locate a fault onthis regular boiler.

The boiler doesn't appear to be sparking and after a few seconds goes to lockout.

So far I have tried the following:

Changed the board (There are two of these boilers running together so I have swapped a few bits over!)

Changed the Ignition unit

Checked the over heat stats in the flue, flow and burner - all OK

Checked the Flow and Return Thermistors - OK

Checked continuity of the wiring to the ignition unit - OK

Checked voltage at Ignition unit I get 230V for around 3 - 4 seconds then itdrops down to 3V

Fan is running OK as is the pump.

And of course checked that there is gas to the gas valve!

Anything else anyone can think of I would be very grateful!

John

 

[JUpton]

Problem traced to fan assembly. Fan is running too fast (High speed) therefore gas valve dosen't open and no spark.
Problem is trying to get hold of parts - NIGHTMARE!

 

[diamondgas]

Never heard of the boiler but a fan too fast is a new one on me? Is it a zero presure valve?

 

[JUpton]

Yes, its a zero governor. The fan when it starts up normallyruns slowley then the boiler ignites. After that the fan speeds up to fullspeed and ramps up and down as and when required. In this case when it startsup the fan immediately ramps up to full speed and the ignition sequence failsto run.

 

[diamondgas]

Looking at the mi's the fan may have a non return flap incorporated in it. If it's anything like the one on some worcesters or the viessmann vitodenz they stick and don't allow the fan to draw the gas through. Worth checking out?

 

[diamondgas]

If the sequence is out of sink I'd be thinking towards whatever controls the fan speed/ignition sequence.... Have you tried swapping the fans? As soon as the fan runs it should be drawing gas through it .. try your monometer on the P2 burner pressure and see what you're reading .. It should initially go minus, pre-purge, then when gas valve opens equalise to zero yeh?

 

[JUpton]

Yes you are right. I have swapped the fans and initially the boiler that wasn't running ran! (Great) BUT today after about 24 hours that fan also went down doing exactly the same thing so now I have 2 boilers not running and an unhappy customer!

I swapped it back onto the boiler that was running yesterday but it is exacly the same so it looks like both fans have now gone down (Unusual).

When I took the fan(s) out I checked the non-return diaphragm and they are both clean and in good condition.

As the sequence dosen't start the gas valve dosen't open so I get no gas to the boiler. I have swapped over the PCB's and the one from the first boiler problem ran in the second for about a week without any problems so the problem can't be coming from that source.

 

[diamondgas]

The self diagnostics looks quite good on this boiler, the mi's I'm looking at are for the Wolf CGB35/50... What code's are you getting? And do you have the mi's. Might seem a daft question ... !

This boiler seems to check the fan has reached pre-purge speed before it will start the ignition sequence..

 

[JUpton]

There is no display on the front of this boiler so I have no fault codes. I know you can get software to run the diagnostics but I'm not sure where from or what hardware you need.

 

[JUpton]

Do you have a link to any info on the boiler. I have a UK manual for it but the tech. trouble shooting is very basic and it basically just tells me to check there is gas at the gas valve and press reset!

 

[diamondgas]

Yeh you're right it looks like some kind of accessary or you plug a laptop in? Do you have the mi's? It certainly sounds like the fan is not carrying out the pre-puge sequence so it is not going to ignition.

 

[JUpton]

Not quite sure what you mean by Mi's

Continuities were all good through the over heat stat / flue stats on both boilers

Thermistors were reading around 12K ohms which for the temp looked OK and again these were roughly the same for both boilers. Apart from these there are no other sensors on the boiler which is why everything seems to point towards the fan(s) (frustrating)

Many thanks for your help just working through the options might bring on a light in my head!!

 

[diamondgas]

JUpton, mi's=manufacturers instructions, sorry! Do you have them to assist you?

I'd agree with you that it is seeming most likely that the fan's or playing up. Remember if these were installed together they're most likely from the same batch and of very similar wear & tear! It can get really frustrating when you've covered everything and it still doesn't work. That's usually when I call in a second head or manufacturers! From what you're describing however the boiler does not seem to be getting beyond pre-purge to ignition stage. On pre-purge the fan will run on full for a certain period of time. By the looks of the fault finding the boilers pcb monitors the speed of the fan and will lock-out if it doesn't reach the desired pre-purge speed. To me that is either the fan or the fan speed monitor(PCB). I will also reiterate that I have not worked on this model/manufacturer of boiler but do have experience when it comes to repairs. If I was where you are I'd be wanting to talk to the manufacturers technical department with the boiler in front of me!

 

[JUpton]

Yes, your right. Problem being they are in Germany and it looks like there is no UK support mechanism. I have emilled the manufacturer so will wait and see what comes back. Couldn't happen at a worse time being a bank holday as well!

Thanks for your help and advise.

John

 

[diamondgas]

Let me know how you get on John. You never know there may be someone comes on who has had a similar experience with this particular appliance and be of greater benefit for you .. I'd like to know the outcome for my own experience though, if you don't mind

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Just re-read the thread and realised I missed a couple of your posts John! So you do have the manufacturers paperwork. The PDF I have is 96 pages thick. If you'd like a copy pm me your email address and I'll send you a copy. I downloaded it from a subscription website...

 

[JUpton]

Thanks Steve



I will post the outcome as soon as I get there!

 

[Billy Bob Bob]

about to read the mi,s as dg has sent them to me but a few things jump out basics first have you checked for reversed polarity? and no mention of the ignition /detection circuit have you checked for continuity on both probes/leads?,this is pointing towards polarity issues, with your 12k on the thermistor did it decrease with temp? or did it not run that long?

 

[JUpton]

I did think about reverse polarity but until today one of the boilers has been running continuously and they are both wired together so discounted this (no harm checking next time I'm in though).

I checked the continuity on the probes, leads to ignition unit etc. all OK

Cheers

 

[Billy Bob Bob]

i would take a further look at revered polarity dont discount custards being economical with the truth or faults in the wiring,the second fan has died on the faulty boiler,this tels us that alls not well with the electrics most pre mix band a boilers have a mini pcb in the fan,but normally r/p takes out the main board but i have seen weird things happen ,out of curiosity does the conden trap have a ignition(short if blocked) fly by wire? if it does worth checking this as well

 

[JUpton]

Will check the RP. I am worried that if I replace the fan on the initial boiler that failed that the new one will go the same way, and at about £250 quid a shot is a bit scary!
The condensate trap has no sensor just drops out the bottom of the burner assembly into a U bend and is pumped away (boilers in cellar).

 

[Billy Bob Bob]

ok check for RP and come back with your findings between all of us on here we will get this fault sorted

 

[JUpton]

Many thanks for all the help

John

 

[diamondgas]

I agree with 'gasman', double check the basics then personally I'd be dead honest with your customer and make sure they're up for paying for your educated guess!

 

[JUpton]

Will do

Thanks Guys

 

[JUpton]

Update on the above

Having gone back and tested everything (again) I have now replaced the fans and both boilers appear to be running fine. There was no issues with reverse polarity. Having inspected both fans there is evidence of water damage to both of these units. I contacted Wolf in Germany and they informed me that water damage to the fan is one of the most likely causes (which seemed to be the case). Having spoken to the owner of the property he did have the flue openings sealed up a few months ago so before this there was possibly an issue with rain water running down the outside of the flue and on to the top of the boiler and eventually making its way inside the case and dripping on to the fans as there is evidence inside the boiler (mainly the first one that went) that this was the case.

SO! fingers crossed, they will be back in working order for a few more years.

Many thanks to all that helped on this

John