EV charger causing ground overheating

[redfox88]

Had an EV charger installed in July last year. It’s wired directly off the mains.

Since end of November anytime I plug the car in to charge, the earth/ground wire in the cabling in other appliances in the house is overheating and melting components of the appliance until the main RCD trips.

Has anyone ever seen or heard this happening before and what could be happening?
Even appliances isolated by switch fuses, when off are getting impacted. It’s concerning.

Electrician has been doing tests but is not quite sure what could be causing the fault

 

[James]

Sounds like a fault with the incoming neutral
it is disappointing that the electrician is struggling to find the fault.

 

[westward10]

Can you show a picture of your main electrical service head.

 

[westward10]

Sounds like a fault with the incoming neutral
it is disappointing that the electrician is struggling to find the fault.

Yep my first thought.

 

[redfox88]

Can you show a picture of your main electrical service head.

This probably won’t help much. Previous owner seems to have built out the wall burying the cables from the meter behind it. Been waiting a year for networks to come out to assess and upgrade this part of it

 

[Lucien Nunes]

It sounds like your supply cable has a combined neutral/earth connection that has become disconnected upstream within the DNO's equipment, possibly in the service head but also possibly in the road. The load current, of which the car charging is the heaviest, is flowing from its own circuit neutral to the point at which neutral and earth combine in the DNO's service terminal equipment, then back down fortuitous earth paths in various other circuits that are not intended to carry such large currents.

If this is actually the case, there is a likelihood of serious damage, fire and shock, and it probably isn't the fault of your installation. The DNO will attend as an emergency as there is a risk to life from all earthed equipment suddenly becoming live, if the fortuitous earths give out. Unfortunately, this particular scenario doesn't normally cause RCDs to trip as they cannot 'see' the problem which is upstream of them.

Don't use heavy loads, get it sorted immediately. I too am surprised by the response of the electrician. I would expect to be able to diagnose this conclusively within about 30 seconds. Unless there is some other completely bizarre explanation like trolls under your floor using arc welders.

The meter and head absolutely should not be boxed in like that, and the DNO would insist that the obstruction be removed in order to inspect. The problem might be right there behind the 'wall.'

 

[westward10]

As above two us immediately thought a supply neutral problem (I suspect your earthing system is TN-C-S), any competent electrician should quickly assume this.

 

[nicebutdim]

Going to tag @LastManOnline in this as I'm certain he'll be interested in learning more about it.

 

[redfox88]

I should mention, we didn’t realise the EV charger was the culprit until today.
And what ye are saying makes sense because initially car was charging at 1.6kw but when fast setting was switched on and power consumption was upped to 6kw, that’s when we noted the issue.

So does this need to be confirmed by electrician first or should this all sit with the electricity supplier to test, confirm and fix?

 

[Lucien Nunes]

two us immediately thought a supply neutral problem

I think we should be rigorous and say specifically it is most likely a 'combined neutral / earth problem' as a problem with just a plain old neutral would simply cause the lights to go out and not create nasty currents in the earthing system.

There is a less-likely alternative scenario that doesn't necessarily involve the DNO, and that is a multiple fault; the neutral is broken or high-resistance upstream of the RCD, and there is also a neutral-earth short(s) on one or more non-RCD-protected circuits. We can't decide whether this is likely without seeing the arrangement of circuits and protective devices. Or of course, the neutral upstream of the board shorted to earth, which is actually conceivable with that daft arrangement of the tails being boxed in.

Any electrician who knows what she / he is doing, should be able to say 'yup, this is a DNO problem.' or not. It probably is, but if you call them out and it isn't, I don't know what the charges are. Somebody here will, and probably also know how to go about claiming for damage to your wiring through overheating, if their supply is proven to be the culprit.

 

[James]

It sounds like your supply cable has a combined neutral/earth connection that has become disconnected upstream within the DNO's equipment, possibly in the service head but also possibly in the road. The load current, of which the car charging is the heaviest, is flowing from its own circuit neutral to the point at which neutral and earth combine in the DNO's service terminal equipment, then back down fortuitous earth paths in various other circuits that are not intended to carry such large currents.

If this is actually the case, there is a likelihood of serious damage, fire and shock, and it probably isn't the fault of your installation. The DNO will attend as an emergency as there is a risk to life from all earthed equipment suddenly becoming live, if the fortuitous earths give out. Unfortunately, this particular scenario doesn't normally cause RCDs to trip as they cannot 'see' the problem which is upstream of them.

Don't use heavy loads, get it sorted immediately. I too am surprised by the response of the electrician. I would expect to be able to diagnose this conclusively within about 30 seconds. Unless there is some other completely bizarre explanation like trolls under your floor using arc welders.

The meter and head absolutely should not be boxed in like that, and the DNO would insist that the obstruction be removed in order to inspect. The problem might be right there behind the 'wall.'

Always nice to read roughly what I was thinking,
but laid out in a form that can be understood by anyone. You have a fantastic way of explaining things.

 

[freddo]

I want to hear what the DNO say when they see the meter and cutout in that conditon!

 

[snowhead]

I want to hear what the DNO say when they see the meter and cutout in that conditon!

They'll say that they want it uncovered but that they won't touch it and untill the fault is located I doubt they will want anyone else cutting plasterboard, or whatever it is, away when the faulty / loose cable / damaged cutout may be behind there.
I would think they, the DNO (Networks) will want to cut off the supply outside, whether it be overhead or underground before anyone touches it.

 

[redfox88]

Sounds like we’ve a big of a nightmare on our hands…
Things I wish we knew before buying a house…the list is getting longer. This one definitely tops it

 

[freddo]

They'll say that they want it uncovered but that they won't touch it and untill the fault is located I doubt they will want anyone else cutting plasterboard, or whatever it is, away when the faulty / loose cable / damaged cutout may be behind there.
I would think they, the DNO (Networks) will want to cut off the supply outside, whether it be overhead or underground before anyone touches it.

Yes it doesn't help the meter has been moved and mounted on the board covering the cutout. Might find the meter has been bypassed inside the wall

 

[redfox88]

Yes it doesn't help the meter has been moved and mounted on the board covering the cutout. Might find the meter has been bypassed inside the wall

It wouldn’t surprise me if it had ugggh all I can do is laugh in these situations. And also hope the house is still standing when we wake up ….

 

[Lucien Nunes]

I expect the OP gets the message about the urgency of the situation, but to anyone reading this in the future who is dithering about what to do, perhaps because the symptoms are not as clearcut the OP's overheating wiring, don't ignore suspected broken CNE (combined neutral/earth) connections.

This type of fault is rare but it is dangerous. Even when the load is light and none of the CPCs are showing signs of distress, the risk is still present of everything becoming live when some small thing that might be maintaining the earth continuity breaks contact. A good equipotential bonding setup reduces the risk of shock if that happens, but the fortuitous earth path might well be that bonding itself, so if it fails there is no protection left against severe shock.

Things I wish we knew before buying a house…

Don't beat yourself up, it may well be nothing to do with your house or its wiring. It could be a cable under the road that was grazed by a digger bucket in 1973 and has been slowly corroding since, or a very unlucky fracture at an overhead line tap that happens to move more than it should in the wind. But until properly diagnosed on the spot we can't say with any more certainty.

 

[redfox88]

Thanks all… hopefully get it all resolved soon.

 

[redfox88]

Just a wee update for ye

Networks came out. They couldn’t open up the wall. Said I was to do it but they will request permission from their supervisor to do this tomorrow.

As a result they couldn’t do all of their tests. However initially, the one of the live cables into the meter was damaged so needs replacing, neutral at meter was good but they’re not ruling out any damage of cables behind the wall.

Although they believe it’s unlikely a fault on their end…

Will see when they return tomorrow

We did another test today to find that when EV charger runs, we get 4-5 amps on the earth cable.

EV charger is disconnected now until source of issue is found

 

[redfox88]

Got the phone call this morning to say that they won’t do the opening up works and for me to start it, and they’d be here in a couple hours. They can kill the power if needed, if it’s getting dodgy.

Got most cut out to find a few nice surprises. Stopped when I knocked off the main fuse slightly and everything started sizzling