Corroded swa gland - garage CU

Leyland30 · Jun 17, 2017

Hi,

Have a garage consumer unit supplied from the house CU via a 6mm 2core swa. I noticed this morning the gland entering the garage CU was loose so opened it up to tighten up the gland lock nut. Unfortunately it appears the gland as it enters the garage cu has corroded and brocken away from the lock nut. It's only been install 3 years and the other glands show no sign of corrosion. I have suspicions as to what has caused it but would like some other views on the matter. Pics attached. Thanks

[ElectriciansForums.net] Corroded swa gland - garage CU

westward10 · Jun 18, 2017

Condensation?

Flanders · Jun 18, 2017

Agree with westward seen it before and i have always thought it was coursed by condensation.

Flanders · Jun 18, 2017

Agree with westward seen it before and i have always thought it was coursed by condensation.

Toneyz · Jun 18, 2017

The garage is usually only a single brick skin construction if the wall outside face brickwork is getting a lot of rain on it due to it's orientation water will penetrate through and rainwater/dampness may be coming from where the fixings are.

Marvo · Jun 18, 2017

My immediate thought when I saw the obvious corrosion was internal condensation but there's zero evidence of it anywhere else, all the other metalic items in the photo are bright and shiny plus there's no signs of drip/splash marks on any other surfaces, everything else in the photos is spotless. This is why I thought it likely the moisture was coming internally from the SWA cable itself and certainly worth a quick IR test of the disconnected armour to earth.

It would be great if you could give us more info after your next visit Leyland, I'm very interested to here the final solution on this one.

Leyland30 · Jun 18, 2017

Thanks all, marvo I'm also convinced the moisture is eminating from the gland entry point. As you say, the rust is only present by that particular gland. However, the CU is well over a metre from ground level!?

In regards the CU construction material, BG website isn't particularly helpful but a magnet isnt attracted so, as Richard suggests; likely to be Al or alloy.

When I get chance I'll strip it down and provide an update.

westward10 · Jun 18, 2017

Three protective devices with only one compatible with the enclosure.

davesparks · Jun 18, 2017

What a lash up of an installation!

It looks like there is a bit of corrosion around the other two glands at the bottom, and if it is non-ferrous then I'd guess that there's a quantity of aluminium in the alloy which has led to galvanic corrosion.

Richard Burns · Jun 18, 2017

The absence of earthing conductors to the other SWA glands would perhaps indicate that any voltage on the armour of those SWAs would cause a current through the shell of the CU and this would be directed to the incoming supply gland and would be consistent with the levels of corrosion in that the maximum current would be at the incoming earth and lesser current at the circuits passing through the CU.

freddo · Jun 18, 2017

Is the incoming earth actually connected to the earth bar?

Pete999 · Jun 18, 2017

Poor termination method, was the paint cleaned from the CU prior to Glanding, all very well using Piranha washers, preparation is everything, pity they don't teach that on the courses, isn't it?

westward10 · Jun 18, 2017

See what happens when you post a pic, just as well none of us are critical.

Leyland30 · Jun 18, 2017

I envisaged some critique hence why I saved posting pictures of the CU until I got some concensus on the gland.

As long as it's constructive.

You've not seen the house CU yet! (Head in hands)

Wilko · Jun 18, 2017

freddo said:
Is the incoming earth actually connected to the earth bar?

Not any mooore ...

freddo · Jun 19, 2017

No I mean isn't that tail isolated from the earth bar? I don't see any electrical connection between the enclosure and the earth bar
.

Corroded swa gland - garage CU

Leyland30

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westward10

Flanders

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Flanders

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Toneyz

Marvo

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Leyland30

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westward10

davesparks

Richard Burns

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freddo

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Pete999

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westward10

Leyland30

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Wilko

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freddo

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