Burnt Main Downstream Neutral

E

ennaress

• Jul 22, 2017

• #1

Did an EICR opened the CU and found this burnt charred Neutral running downstream of the (main switch). What should I be looking for (other than a replacement tail)?
There were two or three C2 observations that may well have caused an overload - eg 5kW of water immersion wired into the ring final and the oven run off a 13a plug, but the live conductors looked OK.
Installation over 35 years old.
OC or very low IRs on all circuits.
R1+R2 ok as was Zs.
I know one answer would be a whole re-wire, but I want to know what caused this.
Thanks for any helpful replies

 

Pete999

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• Jul 22, 2017

• #2

That CU looks a right mess, I would be looking at the integrity of all connections paying particular attention to the N busbar, what a mess that is.
5KW on a RFC are you sure?
I foresee a CU change on the horizon. As well as some redirection of the RFC if that 5KW is correct, oh my.

 

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T

The Ghost

• Jul 22, 2017

• #3

Loose connection.

 

westward10

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• Jul 22, 2017

• #4

You sure it was 5kw that would be highly unusual if this is domestic.

 

westward10

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• Jul 22, 2017

• #5

You would need a 32A switch or contactor to control it.

 

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S

Squid

• Jul 22, 2017

• #6

The neutral connection is the sheaving degrading or it is the flash from the camera?

Nice amount of copper from the neutrals on show and the looped back live on the B6 breaker.

 

westward10

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• Jul 22, 2017

• #7

How have you come to the conclusion it may need rewiring.

 

Richard Burns

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• Jul 22, 2017

• #8

From the pattern of heat distribution the neutral busbar terminal connection was loose or contaminated and the heat generated as the installation current passed through the resistance exacerbated the damage and increased the resistance and the heat and so on.
That connection should be good for over 100A so overload is an unlikely cause.

 

westward10

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• Jul 22, 2017

• #9

Definitely a loose connection and the link to the neutral bar appears to have got very hot.

 

Midwest

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• Jul 22, 2017

• #10

See, that's what A3 CU's are all about

 

Ian1981

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• Jul 22, 2017

• #11

Where was the combustion on the plastic cu?
Loose neutrals and all that

 

Pete999

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• Jul 22, 2017

• #12

SWD said:

The neutral connection is the sheaving degrading or it is the flash from the camera?

Nice amount of copper from the neutrals on show and the looped back live on the B6 breaker.

Click to expand...

Sheaving???

 

static zap

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• Jul 22, 2017

• #13

Has the insulation at the top of Neutral gone dry/brittle ,
can see where it's "flowed to blobs" .
RCD end doesn't look as tarnished !
(Nip it up - not completed?)
(or later diagnosis/messing about-RCD-tripping)

 

westward10

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• Jul 22, 2017

• #14

Ian1981 said:

Where was the combustion on the plastic cu?
Loose neutrals and all that

Click to expand...

Plastic will often lump together due to its molecular make up when exposed to heat. The heat here was insufficient to cause thermal breakdown of the molecules and hence no gas is released which would be required to create ignition.

 

Midwest

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• Jul 22, 2017

• #15

As an a by, should the owner be told not to use the installation, until rectified?

westward10 said:

Plastic will often lump together due to its molecular make up when exposed to heat. The heat here was insufficient to cause thermal breakdown of the molecules and hence no gas is released which would be required to create ignition.

Click to expand...

You been drinking already?

 

westward10

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• Jul 22, 2017

• #16

Do a lot of fire risk assessments.

 

Ian1981

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• Jul 22, 2017

• #17

westward10 said:

Plastic will often lump together due to its molecular make up when exposed to heat. The heat here was insufficient to cause thermal breakdown of the molecules and hence no gas is released which would be required to create ignition.

Click to expand...

What answer was a proper physics teachers response.
Thank you sir.

 

Ian1981

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• Jul 22, 2017

• #18

westward10 said:

Plastic will often lump together due to its molecular make up when exposed to heat. The heat here was insufficient to cause thermal breakdown of the molecules and hence no gas is released which would be required to create ignition.

Click to expand...

What answer was a proper physics teachers response.
Thank you sir.

 

Midwest

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• Jul 22, 2017

• #19

westward10 said:

Do a lot of fire risk assessments.

Click to expand...

Do you get twitching with a box of Swan Vestas in your hand

 

S

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• Jul 22, 2017

• #20

To cover you behind send the customer a Danger Notice without delay. It looks too far gone to be cured by tightening the screw up. What do you mean by IR is open circuit (OC) ?, if it is how have you got satisfactory r1+r2 ? You have what is known as "guilty knowledge" of a potential fire risk. Ideally tell them it must be isolated and the C.U. replaced immediately, I realise that may not be practical, so send the Danger Notice and make it their problem not yours ! Sorry if I sound like an arse but where there's a blame, there's a claim !! .