Glow Worm - no-one can fix...

10 Dec 2008
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United Kingdom
Here's a problem that has left a number of people stumped. I'd appreciate hearing from anyone who has experienced this at all.

I have a Glow Worm Ultimate FF 50 boiler which was already a few years old when I moved in 6 years ago - I'm guessing it's 12-15 years old. It's a cylinder system, with 2 hot water circuits - one for the house heating and one for the heating element in the hot water cylinder.

It's always worked well up until I had some electrical work done, which involved replacing the existing house fuseboard with a new consumer unit.

Since that time, there has been a major but peculiar problem with the boiler; If I leave the boiler switched off for a period of time (a few hours), when I switch it back on again there is a loud buzzing noise from the circuit board for around 15 minutes. During this time the boiler attempts to light itself, succeeds then immediately cuts out, to start again. This happens constantly taking about 10 seconds for a cycle. The buzzing sounds very much like a relay flicking on/off very fast.

Eventually the boiler seems to warm up a bit, and ignites for the last time, and the buzzing stops. Provided I leave the hot water heating on permanently after this, there is no further problem with the boiler whatsoever.

One thing I will add is that the *electrician* initially installed the consumer unit with neutral connected to the live. This was rectified a couple of weeks later.

In an attempt to rectify the boiler problem, a heating guy came round and replaced the circuit board and also the ignition cable/flame sensor. No change at all.

To me it seems that there is a problem with the ignition circuit, but how to get hold of someone capable of diagnosing this? Glow worm want to charge me £250 to come and look at it, with no promise of being able to get spares....

Has anyone else had this, and knows exactly what the problem is? I'm literally about to splash out on a brand new boiler to overcome this...

Thanks, if you can shed any light on this...
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Could be the gas valve thats buzzing,

The other thing that they have missed is dirt in the pilot flame which is very common on these boilers and also the elctrode itself mihgt be cracked or dirty.

British Gas will do you a fixed price repair for £180 - £200 dependant on location.

The parts should still be available for this.

Double check your electricians work that its Live to Live, Neutral to Neutral. a L - N crossed can flame sensing faults!
sounds like there could be a fault with the supply to the boiler pehaps reverse polarity, live and neutral wrong way round
Are you sure the noise isn't coming from the gas valve, could be a dodgy solenoid?

As usual someone got there first :)
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sounds like there could be a fault with the supply to the boiler pehaps reverse polarity, live and neutral wrong way round

DINK!!! coincides with the electrical work, could even be a poor neutral connection.
could be a number of things, but these are the least of your problems.
call NICEIC as soon as possible and tell them you have a strong suspicion your electrical installation has been installed wrong and that you are worried about your safety.
if you do so much as HALF the tests after installation, it is impossible to reverse neutral and phase.
the guy was obviously clueless, and i doubt he is qualified. NIC should be able to help you and hold him responsible for the cost of rectification.
No properly qualified electrician would ever do that.

It seems that you have employed an unqualified electrician. Your "heating guy" does not seem much more competent. I hope he did not charge you for a new PCB if that was not required.

Any competent boiler engineer should be able to sort out your problem.

For the amusement of the other engineers, I once went to sort out a "boiler fault" on a five year old appliance.

It turned out the owner's father had rewired the flat and whilst doing that he corrected some crossed polarity he found.

The boiler installer had evidently noticed the crossed polarity and just wired the boiler backwards to get it to work but did not leave a warning label on it as he should have done.

Thanks for your (fast!!) responses, these have been very useful.

To update you all - I got the consumer unit totally rewired and the entire house fully tested subsequent to the abomination performed by the original guy. Now I know the electrics are fully in order.

I was very interested to hear about the British Gas flat fee fix; they should be round today before 6. Apparently they either fix the problem, or else don't charge. I'll be very happy to part with £210 (fee for my area) if this is properly resolved.

We'll see...
Again sounds like the gas valve solenoid , but also ensure that the earth path is good. the boiler uses flame rectification.
You did not comment on the new PCB.

If your boiler still has the new PCB then I would not expect the cost of repair would need to be anything like £210.

Its probably just a little cleaning which is needed.

Find out exactly what was wrong and I will tell you how much ( or little ) that could have cost.

Thanks for your additional feedback.

To keep you up to date, the guy from British Gas came round this afternoon and has decreed ..... it's *definitely* the circuit board.

He can't fit it till monday so I'll have to wait 4 days to see whether this is the case.

Any bets on whether this will fix it?
you have to wait for 4 days for a 1-hour job? better than naught i suppose.

my mommy forbade gambling, sorry.
In an attempt to rectify the boiler problem, a heating guy came round and replaced the circuit board and also the ignition cable/flame sensor. No change at all.

But its already a new one !

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