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Topic Title: Well done Merlin Gerin
Topic Summary: ..and why i like pirahna nuts.
Created On: 09 January 2013 08:33 PM
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 09 January 2013 08:33 PM
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impvan

Posts: 769
Joined: 07 September 2005

Called to a remedial on a submain in an old folks' home today.

Local firm had wired a small metalclad board via a SWA cable from the Merlin panel at the intake, probably 3 years ago, to provide visitor's toilets.
PHS came in to install ozone generators yesterday, btu didn't proceed through lack of earthing; so I got the call......

I was expecting to find another case of SWA jointed into a plastic box mid-run (twice last year!!) but no, run intact.

Eventually traced to the paint on the merlin gerin DB being so thick that the edges of the gland's locknut hadn't cut through it, the banjo bolt had only flat washers and must have been sat bang in the middle of the drilled hole & not touching the casing.

Simply remedied with a pirahna nut - but congratulations MG for your Dielectric Paint!!.
 09 January 2013 08:41 PM
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perspicacious

Posts: 7235
Joined: 18 April 2006

Sight of the EIC or subsequent PIR (or EICR) would be interesting......

Regards

BOD
 09 January 2013 08:42 PM
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mossep

Posts: 344
Joined: 05 December 2010

Thats why you should always wire brush off the paint near the gland! Easy done with a brush attachement for a drill.

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 09 January 2013 08:46 PM
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perspicacious

Posts: 7235
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"Thats why you should always wire brush off the paint near the gland!"

And reinstate

Regards

BOD
 09 January 2013 08:51 PM
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Dave69

Posts: 446
Joined: 16 July 2011

In just about every job we do now with swa the spec says that there must be a serrated washer between the gland plate, or hole and the locknut that the banjo must be connected to the gland plate via a tapped hole, if the gland plate is not thick enough for the tapped hole to allow a bolt to be fully tightened then the banjo must be linked to the earth bar within the enclosure with a 4mm2 min cable and a star washer and nut used to secure the bolt, also these nuts and bolts must be either stainless or brass and protected with denso and of course if the cable is glanded into a plastic type box the the banjo must be linked to a suitable earth,,,,,,,etc..

The problem is that really after you drill a hole for the swa gland, the hole should be de-burred and then painted to prevent rusting, etc. gone are the days of just scraping off some paint to get continuity between the gland and gland plate
 09 January 2013 09:10 PM
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slittle

Posts: 3515
Joined: 22 November 2007

Had the same on a merlin switch fuse a couple of weeks ago.

Where the earthing bolt goes through the pre-drilled hole, the serrated washers weren't sharp enough to remove the paint. Found it on testing but took a while to work out why (or where) we had lost the earth.

Cordless grinder had the desired effect to ensure metal to metal contact.


Stu
 09 January 2013 09:44 PM
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leckie

Posts: 1865
Joined: 21 November 2008

Connect a bit of g/y 4.00 sw.mm from banjo to the earth bar and there is no problem. Also I have about 200 serated washers in stock. Can't remember how I got them, there bicc, so everything on my jobs gets one!
 18 January 2013 12:18 AM
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Martynduerden

Posts: 3211
Joined: 13 July 2008

I'm not sure it's a Merlin Gerin fault, the installer was crap!

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Martyn.

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www.electrical contractors uk.com
 18 January 2013 12:55 PM
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Legh

Posts: 3488
Joined: 17 December 2004

No doubt the paint fulfills the new BS EN 61439 criteria ?

Where the paint is thick, I have used a larger pilot hole saw to grind off the paint, then cut the correct sized hole to take the gland..

With boxes installed in garages, sheds, workshops and the like Pirhana nuts two plump pliers and some elbow grease do the job adequately well enough.

The use of an angle grinder would also do the job.

Legh

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