bad electrics affecting boilers

[mehran]

was wondering if any of you can help.

I am a gasman, was call out to repair a boiler. did my basic tests on the electrics and found:

L-N 240v
L-E 141v
N-E 76V

the N-E is the critical one as this buggers up the flame detention on modern boilers. my question is what caused this? and would it need a full re-wire to fix it?

I am asking because the customer got an electrician in that was his advice.

 

[Spark123]

Sounds like a floating earth, could be very dangerous.
It is impossible to say how to resolve it, you'd have to get a sparky to have a look at the system.

 

[ericmark]

Earthing has become a problem in old houses because of the old now banned idea of using water pipes as the earth and as the street pipes have been upgraded to plastic the earth has been lost.

Although banging in an earth rod or using other methods to get an earth may cure the immediate problem if the house is that old that the water was used for earth likely there are also other issues which would mean more than just putting in a rod is required.

However since all items sold in UK must be now to European standards and the German plug can be put in either way up so the two lives can be swapped then modern boilers would need to be designed so that the polarity did not matter so they can be sold in rest of Europe.

So one must assume also an old boiler so the earth problem must be new? In which case inquiry should reveal what has happened to cause loss of earth connection.

It does leave us both gas and electric tradesmen with a problem. On one hand we should not leave an installation in a dangerous condition and on the other hand we are not allowed to make a house uninhabitable without finding alternative accommodation. So does not matter if switched off or left on we are breaking the rules.

 

[mehran]

hi, the boiler is new. I was called out to it to make a warranty repair. the boiler is imported from Holland so i guess it could handle the Germans doing silly eclectics...

what messing up the boiler is its using earth as the return path for the flame detection. its looking for a tiny current to tell it that flame has been made and measure how well the boiler is burning.

the last time i came across this fault was someone(british gas ) had cut the earth to whole house and I thought it could be something as simple as that.

the electrics in the house look to be re-wired in the last 15 years(no guarantee its been done right i know...)so a full rewire looks a bit extreme

 

[ban-all-sheds]

its using earth as the return path for the flame detection.

That sounds a bit dodgy...

 

[mehran]

someone should of told the boiler manufactures that because every one of them use it...

 

[sparkticus]

someone should of told the boiler manufactures that because every one of them use it...

It may look like the earth return path but is it simply using the boiler chassis as a ground? If so then the small (very small) current loop will be within the boiler circuit and not reliant upon an actual connection to earth. Though a floating earth may have an effect on the circuit. Having said that, I have seen a flame sensor (an optical sensor) in a worcester/bosch that has two connections right back to the PC board as I would have expected?

 

[JohnW2]

What everyone (since Spark123's initial response) seems to be overlooking is that what the OP reported is a potentially very dangerous situation, which needs to be looked into urgently. Should we not be reinforcing that message?

Kind Regards, John.

 

[sparkticus]

What everyone (since Spark123's initial response) seems to be overlooking is that what the OP reported is a potentially very dangerous situation, which needs to be looked into urgently. Should we not be reinforcing that message?

That's a good point, the main issue does need urgent attention. This reminds me of the (I have forgotten the actual flight details now) pilot who allowed his aircraft to lose altitude and crash into the ground while he and the co-pilot were fixated on finding out why an instrument light was not on!!!

 

[Spark123]

Was it the one where the lamp was out for the front landing gear and they were fixated in trying to get the lamp to work and didn't realise the autopilot had disconnected?
http://en.wikipedia.org/wiki/Eastern_Air_Lines_Flight_401

 

[mehran]

no need to get your kickers in a twist. I showed and told the customer the electric fault. advised them to get an electrician, they got an electrician, the electrician is going to re-wire the house...

on the boiler, almost every modern domestic boiler will be using Flame Rectification as the way to sense there is a flame. optical sensor are generally only found on commercial boilers