Neutral to earth fault

[nicholas221078]

I'm more just wondering why he says he could change it then couldn't and gave us this fault.
He seemed really genuine and was a nice bloke

 

[terryplumb]

Hi no.
He said I won't charge you before he left .
He didn't charge for quoting or anything either

Well he can't be accused of ripping you off. Maybe he realised the quote was too low ,and the job was going to be more involved /time consuming than first thought.

 

[nicholas221078]

Hi
No , like I say he was a decent guy so definitely not a rip off person.

You maybe right as when I looked the cables looked too short to come further out than the face plate.

 

[terryplumb]

Don't know what he was thinking ,but to tell you that a re wire was required is totally misleading ,as is the demonstration of continuity .
It all seems to me to show a complete lack of integrity ,or incompetence if he believes what he told you.

 

[nicholas221078]

Thanks.
I don't think we will ever know now.
I think we will have to save up again to get someone out to check if it can be just a CU change to get a certificate.

Thanks everyone

 

[SUNRAY]

With the main switch ON, all Neutrals and Earths are connected together.

I'm surprised it took this many replies to get to this albeit only half hour

If what you say is correct, then another electrician would be a good idea.

That sounds right.

 

[markyd1]

Get a proper EICR done on the property...this will show up any faults that need rectifying before the board change

 

[nicholas221078]

Thanks both.
How much is an EICR test usually ?

Thanks

 

[ericmark]

Long story short with the fuse box switched off there's no neutral to earth fault or continuity, only when the fuse box is on.

That is normal, neutral is linked to earth at the DNO transformer,

 

[sparkwright]

To clarify to the op
With the main switch OFF, you should not be getting continuity between N and E.

But he should be doing more sophisticated tests.

Has he said which CIRCUIT has the dead short on it? ie lights, sockets etc?

Did he unplug any appliances when doing this 'test'?

There may not be anything with your actual wiring, he should have investigated further.

 

[winston1]

Thanks both.
How much is an EICR test usually ?

Thanks

Don’t bother. It will (should) be done as part of a CU change.

 

[nicholas221078]

To clarify to the op
With the main switch OFF, you should not be getting continuity between N and E.

But he should be doing more sophisticated tests.

Has he said which CIRCUIT has the dead short on it? ie lights, sockets etc?

Did he unplug any appliances when doing this 'test'?

There may not be anything with your actual wiring, he should have investigated further.

Hi
He didn't mention a dead short or anything .
Just showed me the buzz from neutral bar to the earth bar.
He didn't test any further.
Didn't un plug any appliances etc.
He might have thought well I gave a set price for the CU change and its more effort now than he thought.
I'm unsure.
He didn't say there was in issue with anything else .

Thanks

 

[terryplumb]

Is it possible that you have misunderstood ,and there is continuity between neutral and earth with the power OFF ??
Bit of a long shot I know !!!

 

[nicholas221078]

Hi.
I'm quite savvy in that respect being an engineer i like to watch lol, he defo did it with it on.
He had the mcbs out, when he showed me he then switched the CU off and re installed the mcb units .

As I was in view before he called me (from hallway ) I looked round and he went across the neutral block to earth block with the switch off and there was no buzz from his multi meter , he then switched it on and did the same and his meter buzzed .

He then called me as he couldn't actually see me but I could see the CU I stepped round and he said what I put and showed me .


At the time i didn't think anything of it apart from oh no.

It's only a week later I'm thinking about it and thought I'm not sure if he was correct.

Cheers

 

[ericmark]

As I said before that is normal, at the DNO transformer earth and neutral are linked, with a TN-C-S also use the same cable, with TN-S and TT the voltage between neutral and earth can be higher, maximum permitted with AC is 50 volt between neutral and earth except with electric car charging where is can be higher, personally think that is wrong, but still permitted.

The use of an earth rod (TT) does allow with no fault a higher difference between earth and neutral it is the resistance of the neutral wire which allows the voltage to climb, in general no more that 10 volt.

To fit a new consumer unit we need to consider

Every installation shall be divided into circuits, as necessary, to: (iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation

this is a problem with a new installation as we really have no idea of what equipment will be used, so down to experience, and common practice. But with an existing house it is reasonably easy to measure the back ground leakage, two basic methods, this meter measures DC leakage with circuit isolated, and these meters can measure the AC leakage with the circuits live, we are allowed 1/3 of the rating of the RCD to leak under normal operation so limited to 9 mA with a 30 mA RCD, however over 3.5 mA we need to take special precisions which increases after 10 mA, so really don't want to see over 3.5 mA leakage.

My whole house everything running as normal has around 19 mA leakage, but since this is spread over 14 RCBO's it is not a problem, but if using just two RCD's it could result in a problem, so we are required to sign that we have designed rather than just thrown it together, the answer of because we always do it that way, is not acceptable when asked why have you done that. However it is often why things are done.

We should consider if it is likely there will be nuisance tripping, with a caravan the whole unit is protected by two 30 mA RCD's in series, same with narrow boats, however in the main they have 12 volt DC lighting from batteries, so even a small flat one would want at least two 30 mA RCD's unlike the caravan in parallel so forming two independent circuits, as the property increases in size we need to consider if a RCD trips will it cause the home to be plunged into darkness, and also if a fault can't be found, can essential equipment be transferred to a good circuit, like freezers, and when doing this would it require extension leads to be run up/down stairs, as clearly that would cause a danger. My house sockets split side to side not up/down, so no need for an extension lead up/down stairs. But old house street lamp right outside, so never really fully dark even with an RCD trip, this house use automatic rechargeable torches which switch on with power cut. This can be taken into consideration, however the electrician is still responsible for the design.

It is not a blind following of the rule book, but more common sense.

Today the electrician is required to liaise with the owner, he should not force things like surge protection devices (SPD) on the owner, but he must explain why they should be fitted, the same goes for all RCBO (RCD and MCB combined) or RCD with multi MCB's, not an easy task, as I am not really sure myself as to what is really required and what is a knee jerk reaction but people like the London Fire brigade.