Worcester Bosch wires melting

[redd]

Hi

about an hour ago all the lights in my house tripped out. I went to the fuseboard and one switch was down. Flicked it back and it tripped out immediately.

few moments later theres and acrid smell and a little smoke in the room

tracked the smell down to the boiler, took the cover off and was met with this (see photo)

have got someone coming out tonight to look at it. In the meantime have turned the power off.

Any idea what would cause this earth wire to melt?

It’s a Worcester Bosch junior 28, has been in about 8 years without any problems

 

[centralheatking]

Go to the white box adjacent to the boiler, it will have a fuse access panel. Turn the switch off take out the fuse. I may have a red monitor light as well which will go out. You have been very lucky.
centralheatking

 

[redd]

Go to the white box adjacent to the boiler, it will have a fuse access panel. Turn the switch off take out the fuse. I may have a red monitor light as well which will go out. You have been very lucky.
centralheatking

cheers, have just done that

When you say ‘very lucky’, I’m guessing we were close to a big bang or fire?

Any idea what would cause this? I’ve had a good look and it’s just that earth wire that’s melted and scorched the plastic casing.

Also, the powers now isolated for the circuit it’s on. Presumably I can keep the gas and water on? (Engineer coming later on)

 

[SJB060685]

Looks like a ground fault somewhere, do as said above and have your guy look at it.

Note your RCD has done its job and the fuse may not have blown

 

[Chuck]

Any idea what would cause this earth wire to melt?

Tens, if not hundreds of amps flowing as a result of an uninterrupted fault. The boiler should have been protected by small fuse, typically 3 amp, in its mains supply, which would have prevented this. My guess is the boiler was wired into an unfused, or incorrectly fused, junction box.

You're lucky you still have a house and any occupants are alive. Get Bosch to repair the Boiler and a properly qualified electrician to check its supply. (It would be prudent to get them to check the whole house while their at it.)

 

[centralheatking]

As Chuck stated if your boiler does not have a white box adjacent with a 3 amp red fuse then your trip has done its job, picked up high demand and saved you. Take this very serously indeed that earth wire has melted due to heat the source of the problem needs tracking down. chking

 

[redd]

Thanks all, That’s quite frightening

I’ve taken a look and you can see where the earth wire has melted into the adjacent grey wire (see pic). You can see the scorch marks on the casing too.

no other wires in the boiler seem to be affected

 

[Murdoch]

Interesting that the "earth" cable seems to be damaged - unusual to say the least.

Looking at the photo I wonder if the connections to the blue item "connected" to the earth cable and created a dead short - in this case I would have expected the 3A fuse in the boiler supply to fail - was the switch down the MCB or RCD?

 

[redd]

Tens, if not hundreds of amps flowing as a result of an uninterrupted fault. The boiler should have been protected by small fuse, typically 3 amp, in its mains supply, which would have prevented this. My guess is the boiler was wired into an unfused, or incorrectly fused, junction box.

You're lucky you still have a house and any occupants are alive. Get Bosch to repair the Boiler and a properly qualified electrician to check its supply. (It would be prudent to get them to check the whole house while their at it.)

I’m thinking the adjacent fuse box has been bypassed. As I turned it off on one of my attempts to get the mains power back on, yet it all tripped out regardless.
[automerge]1578314630[/automerge]

Interesting that the "earth" cable seems to be damaged - unusual to say the least.

Looking at the photo I wonder if the connections to the blue item "connected" to the earth cable and created a dead short - in this case I would have expected the 3A fuse in the boiler supply to fail - was the switch down the MCB or RCD?

Switch was down on the RCD

 

[ShaunCorbs]

Interesting that the "earth" cable seems to be damaged - unusual to say the least.

Looking at the photo I wonder if the connections to the blue item "connected" to the earth cable and created a dead short - in this case I would have expected the 3A fuse in the boiler supply to fail - was the switch down the MCB or RCD?

sparker so probably the the high voltage wire had a bit of the insulation missing so arc across

 

[SJB060685]

As these guys have said there should be a 3 amp fuse on incoming live to boiler system. Like I said though IF you have a bank of MCB's protected by an RCD this will have tripped before the fuse in the event of an imbalance most probably. If your fuse board hasn't got RCD's then the MCB will have tripped do to the ground fault overload

 

[Murdoch]

In the case of a dead short, whether the 3A blows, the MCB in the fuseboard or RCD trips is never consistent - sometimes its the RCD and the fuse or MCB...

Often see such faults in back boxes where the box isn't deep enough and the cables are crushed together - then its a matter of time before the sleeving fails ........ then the bang and the black scorch mark

 

[centralheatking]

cheers, have just done that

When you say ‘very lucky’, I’m guessing we were close to a big bang or fire?

Any idea what would cause this? I’ve had a good look and it’s just that earth wire that’s melted and scorched the plastic casing.

Also, the powers now isolated for the circuit it’s on. Presumably I can keep the gas and water on? (Engineer coming later on)

Well done you are ok now, sit back ...cuppa tea and wait for experienced electrician...do let us know what he says as we like feedback it helps us to learn more. centralheatking

 

[SJB060685]

To answer your question redd yes fires can be caused from faults like this, however the fuse and MCB should protect the system from this. RCD's protect people from a shock and work by detecting an imbalance between phase and neutral current, ie when theres an earth fault like you've just experienced

 

[bacon_sandwich]

yep, leave the breaker off. Burnt out earth wires can be a sign of another fault not related to the boiler.

 

[centralheatking]

yep, leave the breaker off. Burnt out earth wires can be a sign of another fault not related to the boiler.

It would appear that PF can do electrics ....well done all...just goes to show We are the Senior Trade
always knew this anyway did we not ! ? ....centralheatking Is there an Electricians Forum ? yes its under a stone
somewhere but nobody knows where ....chking

 

[SJB060685]

I have a very good understanding of electrics, I like to study it in my spare time but I'm not an electrician and I certainly wouldn't argue with Murdoch or any other qualified person

 

[centralheatking]

I have a very good understanding of electrics, I like to study it in my spare time but I'm not an electrician and I certainly wouldn't argue with Murdoch or any other qualified person

Its always important to know ones limitations ...I do. chking

 

[redd]

Thanks for all your help chaps

will report back with the diagnosis later

 

[bacon_sandwich]

Have a degree in electrical engineering and do frequent the other forum, lol
I tend to only look at ops that are either pure gas or electrical, my best friend is plumber

 

[centralheatking]

Have a degree in electrical engineering and do frequent the other forum, lol
I tend to only look at ops that are either pure gas or electrical, my best friend is plumber

I have a friend who is an Electrician we have had him with us for years...we drink with him
...his name is 'Mad Ian' ..he is quite often 'short on his round' usually never buying me a beer before he slopes off ...but we like and most importantly trust him.......centralheatking

 

[OffshoreGas]

Thanks for all your help chaps

will report back with the diagnosis later

Looks more like a fault for a sparky than a plumber to me.

 

[redd]

Man has been to check the boiler and seems to think it's an electrical fault somewhere on that circuit. the wiring in the fuse box next to the boiler looks a bit dodgy, live and neutral wires both have cuts in them and the earth wire sleeve has melted there too

Electrician coming tomorrow.

Thanks for all the advice on here

 

[SJB060685]

I imagine the ground fault is somewhere inside the boiler somewhere. Lots of places and components where this can happen. I hope this sudden rush of current hasn't damaged any more parts. Might be advisable to have both electrician and engineer there at same time

 

[redd]

We’re back in business!

Looks like it was a plug socket in the kitchen (same circuit as boiler) that was at fault. As the electrician took each socket on the circuit out one by one, this one was all burnt out inside. The live wire had melted onto the earth cable. He says the live wire wasn’t secured in the terminal properly and had just come loose over time.

presumably this had made the earth wire ‘live’?

I’ve no idea why it then went into the cellar and nearly set the boiler on fire, when everything else is fine?


Anyway a couple of new sockets later, plus new fuse and socket fitted to boiler supply and all seems well.

 

[SJB060685]

We’re back in business!

Looks like it was a plug socket in the kitchen (same circuit as boiler) that was at fault. As the electrician took each socket on the circuit out one by one, this one was all burnt out inside. The live wire had melted onto the earth cable. He says the live wire wasn’t secured in the terminal properly and had just come loose over time.

presumably this had made the earth wire ‘live’?

I’ve no idea why it then went into the cellar and nearly set the boiler on fire, when everything else is fine?


Anyway a couple of new sockets later, plus new fuse and socket fitted to boiler supply and all seems well.

If the live was loose then it like he said over time it will work its way out of connector. You are right to a degree, the live wire when comes in contact with the earth creates a circuit back to source, without a resistive load you have a sudden, massive rush of current, this rush of current (over current) generates heat and melts any fuse or trips any MCB, which is what they're supposed to do, protect the system and prevent fires.

 

[bacon_sandwich]

Great news. Earthing within a house can have many parallel paths. The boiler and associated pipework can be a good hub for many parallel paths. The good news is that the breaker did its job and saved more serious damage to the property. Hopefully the electrician has checked all associated devices that were on that cct as its certainly stressed ALL earth routes back to the consumer unit.

 

[redd]

If the live was loose then it like he said over time it will work its way out of connector. You are right to a degree, the live wire when comes in contact with the earth creates a circuit back to source, without a resistive load you have a sudden, massive rush of current, this rush of current (over current) generates heat and melts any fuse or trips any MCB, which is what they're supposed to do, protect the system and prevent fires.

yeah, pretty lucky I suppose!

Going to get them back to fit a new consumer unit and rewire that circuit shortly, as it looks like it’s been in since about 1970

thanks everyone on here for the advice

 

[Murdoch]

We’re back in business!

Looks like it was a plug socket in the kitchen (same circuit as boiler) that was at fault. As the electrician took each socket on the circuit out one by one, this one was all burnt out inside. The live wire had melted onto the earth cable. He says the live wire wasn’t secured in the terminal properly and had just come loose over time.

presumably this had made the earth wire ‘live’?

I’ve no idea why it then went into the cellar and nearly set the boiler on fire, when everything else is fine?


Anyway a couple of new sockets later, plus new fuse and socket fitted to boiler supply and all seems well.

Whilst that may have been identified, this doesn't explain why the "short" didn't use the circuit CPC (earth) back to the fuseboard .......... which is what I would have expected unless the circuit cpc wasn't connected at the fuseboard.

Was this circuit a Ring or Radial and was it tested properly for continuity?

 

[SJB060685]

Whilst that may have been identified, this doesn't explain why the "short" didn't use the circuit CPC (earth) back to the fuseboard . which is what I would have expected unless the circuit cpc wasn't connected at the fuseboard.

Was this circuit a Ring or Radial and was it tested properly for continuity?

Hi Murdoch.

I'm always keen to further my knowledge about electricity. Can you explain to me why this ground fault may have taken this path rather than back to fuse board?

 

[Murdoch]

Hi Murdoch.

I'm always keen to further my knowledge about electricity. Can you explain to me why this ground fault may have taken this path rather than back to fuse board?

Maybe my poor response but the reason for ALL 240v cables in a domestic setting to have a CPC (earth) which is continuous from the fuseboard to the end of the circuit is so that this earth is the path such a fault would take. This includes lighting circuits

If under fault conditions, the fault took "another" path back to the fuseboard, this would suggest that the circuit with the fault did not have a CPC (earth) back to the fuseboard.

In the fault as described, the lack of earth would explain the unusual "path", which took another route back to the fuseboard.

On a slightly different subject, boiler wiring, for mains powered room stats don't always show the CPC, but it must be connected to the boiler ......... or else in the event of a fault, the current will find another path - which could well be you!

 

[SJB060685]

Thanks for explaining. Silly question. What does CPC mean mate?

 

[Murdoch]

C ircuit
P rotective
C onductor

or earth!

 

[SJB060685]

Yes I got it, thanks

 

[redd]

Whilst that may have been identified, this doesn't explain why the "short" didn't use the circuit CPC (earth) back to the fuseboard . which is what I would have expected unless the circuit cpc wasn't connected at the fuseboard.

Was this circuit a Ring or Radial and was it tested properly for continuity?

the electrician did say that the electrics in the property weren't earthed, and were relying on an earth on the gas and water pipes?

He advised me to call my supplier (E-On) and get them to sort this earth out. After half an hour on the phone to Bangalore or somewhere, Ive got someone coming tomorrow to fit a smart meter ffs. Despite telling the chap countless times I need someone to look into the incoming connection, he insists its something they'll deal with as part of the smart meter install. The cynic in me suspects he's taking cr@p and is on commission for getting someone out to install a smart meter

Would this usually be the job of the DNO (northern powergrid in this case), or something I should get my own electrician to sort?

 

[Murdoch]

the electrician did say that the electrics in the property weren't earthed, and were relying on an earth on the gas and water pipes?

He advised me to call my supplier (E-On) and get them to sort this earth out. After half an hour on the phone to Bangalore or somewhere, Ive got someone coming tomorrow to fit a smart meter ffs. Despite telling the chap countless times I need someone to look into the incoming connection, he insists its something they'll deal with as part of the smart meter install. The cynic in me suspects he's taking cr@p and is on commission for getting someone out to install a smart meter

Would this usually be the job of the DNO (northern powergrid in this case), or something I should get my own electrician to sort?

Sounds like you need a new electrician ...

Did said electrician give you any paperwork for your work ?

 

[redd]

Sounds like you need a new electrician .

Did said electrician give you any paperwork for your work ?

no paperwork yet, other than a bill

What makes you say that anyway? I’m guessing you’re suggesting the electrician should be the man to sort out this earth issue rather than my supplier or DNO?

 

[bacon_sandwich]

If the electrician has determined that your house has no earth, then this is in fact a very different (and quite dangerous) situation, a photograph of the consumer unit, meter and incoming service head would be useful for us.
Treat this revelation as very urgent to fix.

 

[Murdoch]

no paperwork yet, other than a bill

What makes you say that anyway? I’m guessing you’re suggesting the electrician should be the man to sort out this earth issue rather than my supplier or DNO?

No decent competent spark would leave you in this situation without some form of written note for the client to understand

There are homes around without an earth, there are home around that use gas or water pipes for the earth .... only a private metal water supply pipe can be considered suitable for use as an earth ....

Where does the electrical supply enter your home? Overhead or under ground?

Not enough information to comment further tbh and I would recommend you get a 2nd opinion ...

Maybe the op could post some pictures

 

[redd]

The electrician says it has an earth, but it’s not sufficient and it’s not with the electrical supply? It’s on the gas and water pipes?

The house has a normal underground supply, all the utilities are in the cellar

Here’s a pic of the fuseboard setup and the earthing around the boiler gas and water pipes...

 

[bacon_sandwich]

OK, I cannot see any green or green/yellow cable coming from the service head, black block on right, i also cannot see any device that would be used if your service has an earth rod somewhere in your garden. You have no additional protection for earth faults in your fusebox that we have on more modern installs. So basically its as pointed out probably the only meaningful earth is via the water pipe. This is not good. You need a proper earthing system as nowadays gas and water supplies are quickly being fed via plastic pipes so you may have only a short bit of pipe actually to earth.
There are much better ways of earthing available which will stop further faults melting random earth wires in your house.
Good call to get supplier in to give you an acceptable modern earth for your house.

I do a lot of testing and have a feel for whats going to pass. I would bet that your current install cannot trip the breakers in the required time, this is bad and you may well be at risk.

 

[Murdoch]

Interesting pictures.

No RCD, no suppliers earth (could be a TT supply) but there appear to be green & yellow cables exiting the fuseboard from the top - so is there a TT earth rod outside. You also need to get the installation checked to see if there is any equipotential bonding in place too!

You may not get an earth from the supplier (if it is TT) and you will need a competent spark back.

Your fuseboard needs updating and RCD protection adding - I would recommend a new board with RCBO's

Could be an expensive January for you - but potential life saving money to be spent

Hope this helps