Discuss Car Charger 6mm SWA cable Query - Loft Insulation in the Electrical Forum area at ElectriciansForums.net

shefbengal

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Hi

We recently had an 7kW EV charger installed. Due to the consumer unit being situation within the kitchen of our bungalow, the cable needed to be routed across the loft in order to end up next to the drive,

The contract was with a well known brand, who has sub-contracted out the installation work.

I believe it is 6mm SWA that has been used in the loft. The span over the insulation is roughly 9 metres. Prior to the cable being installed by the installer, there as insulation roughly 200mm.

The cable has been clipped to the ceiling rafters, but the loft insulation material has been completely moved to the side for the run. Attached are before and after install photos.

I have tried googling the SWA cable de-rating tables - some are suggesting a derating of 50% for insulation up to 100mm.

Where I got to was 7kW charger = 32 Amps. 6mm cable rated for 53 amps (in air presumably). Clearly, derating the cable down to 26.5 amps is short of the 32amps the charger is capable of using.

Would you expect a thicker cable to have been used in this installation as I really don't want to lose a section of loft insulation? Or, am I fine to move the insulation back into place so that it will be besides and over the cable (as it was prior to install)

I have queried the above from the installer and I am being ignored,

I would really greatful if anyone could provide any thoughts. Are my calculations way off?

Thanks..
 

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bill01803

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You are correct, the cable isn’t big enough for in insulation.
As this is notifiable work I presume that the contractor is registered so you can complain to the body ie. niceic/napit and they will do nothing.
good luck.
 

timhoward

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There’s one small error I think.
If it’s a domestic single phase supply then 6mm SWA is rated for 62amps clipped direct. I think you looked at the 3 phase column.
Which makes it 31 amps when de-rated.

Technically 1 amp too low. But these values are for the cable being at 90 degrees C.
Could you not leave a small 3 inch channel in the insulation for it?
 
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shefbengal

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Many thanks. Yes, they have notified the work and provided a copy of the cert to building control.

What I may do is commission an independent report just confirming the situation on writing, then proceed along a section 75 claim against the credit card company or perhaps a charge back,

Hitting them financially will likely invoke a response rather than a drawn out complaint to a so called scheme.
 
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shefbengal

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There’s one small error I think.
If it’s a domestic single phase supply then 6mm SWA is rated for 62amps clipped direct. I think you looked at the 3 phase column.
Which makes it 31 amps when de-rated.

Technically 1 amp too low. But these values are for the cable being at 90 degrees C.
Could you not leave a small 3 inch channel in the insulation for it?
yes, it is a domestic install. I may well have read the tables incorrectly.
 

loz2754

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I would not be happy with that installation.
Removing insulation and not refitting it is very poor practice.
And it would seem that the issue of the cable passing through insulation has not been even considered in the design. Maybe ask to see a copy of the design calculations? (But don't hold your breath...)
If you're not satisfied, you should take it up with whoever you paid the money to, as your contract is with them.
 

mattg4321

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It’s not strictly correct but it might be less stress and hassle to you to leave a small space in the insulation around it.

Also I expect it could be NYY or H07 cable rather than SWA
 
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shefbengal

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Part of my reason for wanting to look into this was the fact they were quite happy to install additional 10mm earth with the following routing.

To set the context after a remote survey requesting photos of the current bonding and agreeing a price on the day I was charged an extra 150 for this earthing work. I appreciate they can’t tell wire diameter from requested quote photos but I had hoped for a little more thought on cable routing in such a prominent position. They reluctantly agreed to house it in black conduit - which covers the blown out brick face. Oh and guess where all the holes were drilled for the saddles? It wasn’t the mortar line!

Re the loft cable. I might just do as suggested and give it a little room as suggested. Life is too short sometimes.

Finally to be fair. The install of the actual charger box is neat and tidy on the drive. I appreciate the contractors are prob under pressure to bang these out quickly and as cheap as possible.
 

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Gavin John Hyde

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They reluctantly agreed to house it in black conduit - which covers the blown out brick face. Oh and guess where all the holes were drilled for the saddles? It wasn’t the mortar line!


Finally to be fair. The install of the actual charger box is neat and tidy on the drive. I appreciate the contractors are prob under pressure to bang these out quickly and as cheap as possible.
Would have been easy to drill from outside into the loftspace given its an empty void! in terms of drillign holes for the saddles I will give them benefit of the doubt as sometimes drilling into mortar can see it crumble and moment you tighten a screw you cant get a good fixing as the saddle pulls in the curved recess between bricks.

Yes, a lot of these national firms expect 2 or 3 installs per day. at the lowest possible cost!
 

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