SWA questions, doubting electrician

[LeeH38]

Recently had an electrician in to wire up power to a detached garage and also wire in a 32 amp rotary switch for an eventual hot tub install.

He has used a spare 40amp MCB in the house consumer for the garage and a 32amp one for the hot tub point. Cable run for both is about 10m each.

He left on Friday and the whole side of the consumer in the house tripped immediately and I started having doubts about other things then as part of the kitchen is also on that side of the consumer and hasn’t been touched. I then switched the two new circuits off and the consumer continues to trip whenever I plug anything in in the kitchen. Been promised a visit to sort it out but today I simply removed the new wiring into the consumer to see if I could get the kitchen back up as it’s a nightmare without and everything has returned to normal.

Now having major doubts about the rest of the work and have had another opinion from a retired electrician neighbour and it doesn’t look good. However original installer is saying it’s something simple and everything has been done to standard.

My main doubts are:

1. Is 4mm armoured cable sufficient for this layout. I have a 32 and 6 amp MCB on another board in the garage run from the 40amp MCB on the house board. This is to run 8 sockets and 4 led lights.
2. Is 4mm armoured cable sufficient for a hot tub. I am led to believe it should be 6mm.
3. Non of the armour part of the cable is earthed, he reckons it’s fine as it’s 3 core and earth is inside. I don’t believe this though and think it needs earthing at the house consumer at the very least.

I am struggling to have a reasoned discussion as he is the electrician and I’m reading stuff on the internet, I wouldn’t have even started searching had I not had the initial issues.

Meant to be inspected and a certificate off someone else this week but not sure that means much tbh?

Any advice on how to approach this very much appreciated.

Thanks,

Lee

 

[Strima]

The tripping could be purely coincidental but without a proper inspection and test we cannot diagnose over the internet.

As for the SWA earthing, the armour should be earthed at the supply end as abare minimum.

How is the SWA installed? If buried or clipped to to a wall then it is not sufficient for the 40 amp OCPD you have mentioned.

 

[westward10]

Any chance of some pics.

 

[LeeH38]

It’s clipped to a wall.
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Of which parts? Will grab some when it’s light if it’s outdoor you need. Cable run is clipped to wall, clipped under steps and a small part runs along the edge of the garden next to the garage base.
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Had this reply when I have questioned the cable thickness too.

For a 24m cable run the max load for a 4mm is 43.5amp its on a 40amp and 13 metres and a 32 amp for the hotub is nowhere near the max demand either

 

[westward10]

A three-core 4mm cable when clipped direct is rated at less than 40A.
Some internal pics at the fuse boards would be good.

 

[SJD]

The tripping you describe sounds like a N to E short on one of these new circuits. If that is the case it should have been found by testing before anything was energised; disconnecting the new cabling will have removed the N to E short.

 

[Andy-1960]

Did he just install a supply cable to a garage that was already wired or did he wire the garage as well?

 

[LeeH38]

Top one is before I disconnected (obviously).
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Did he just install a supply cable to a garage that was already wired or did he wire the garage as well?

Both.

 

[Andy78]

1. No the 4mm armoured cable is rated at 38A clipped direct, the 40A breaker is wrongly selected for the cable size. The claim of 43.5A is incorrect and suspicious as the regulations give cable current carrying capacities in whole numbers.

2. Yes 4mm may be fine for a 32A hot tub supply volt drop permitting, I have seen it where hot tub manufacturers insist on 6mm in their instructions though.

3. Yes the armouring should be earthed as it is an exposed conductive part. If the cable is buried at all then it should be earthed for that purpose too.

 

[westward10]

Can you show below the board where the cables enter.

 

[LeeH38]

Cables just fed through bottom of unit, no earthing.

 

[Andy-1960]

Has he given you any test paperwork? Also this is notifiable work under the Part P scheme, so he should have submitted this to the local council. I agree with SJD it sounds like a neutral earth fault, this should have been picked up if he had tested his work as he should have.

 

[westward10]

What's the board in the garage like.

 

[LeeH38]

What's the board in the garage like.

I’d take some pics but my lights don’t work ? cable is fed into consumer through a rubber/plastic gland and again no earth.

 

[Pretty Mouth]

4mm 90deg SWA would be okay at 40A wouldn't it?

https://www.whyprysmian.co.uk/BS5467.pdf

 

[SJD]

I’d take some pics but my lights don’t work ? cable is fed into consumer through a rubber/plastic gland and again no earth.

As mentioned earlier, the armour has to be earthed at least at one end.

So if someone damages the cable, and shorts L to the armour, it does not make the whole armour live. Which could prove fatal e.g. a buried cable that someone digs into with a metal spade etc.

This is nothing to do with the fact that there are 3 cores, and one is used for the E.

 

[westward10]

4mm 90deg SWA would be okay at 40A wouldn't it?

https://www.whyprysmian.co.uk/BS5467.pdf

Unless the terminals the conductors are terminated at are rated at 90°C then you use Table 4D4A.

 

[telectrix]

the steel armour of the SWA must be earthed, even if only at the supply end, when a 3rd core is used as cpc (earth).

 

[LeeH38]

Well everyone has confirmed what I suspected. Not sure where I head now apart from starting again with someone else. I know someone who can probably correct it but the whole point of using an electrician was for it to be signed off.

 

[westward10]

You say in #1 someone else is signing it off?