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Topic Title: Need advice ??
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Created On: 30 October 2013 05:12 PM
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 30 October 2013 05:12 PM
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goldenboy1818

Posts: 503
Joined: 22 February 2011

Hi all was just after a bit of advice as Iam looking at a job that involves moving a fuseboard position with a submain. Thinking of putting a 100amp switchfuse in the meter box (if swa doesnt need rcd protection ?) then 25mm swa armour out to the new fuseboard position. Obviously extending all cables back to the new fuseboard position Any thing else to be aware of with this job and sub main ?? Many thanks for any advice
 30 October 2013 05:24 PM
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AJJewsbury

Posts: 11699
Joined: 13 August 2003

I'm guessing this is domestic?

100amp switchfuse in the meter box

The supplier might have an objection to that ...

25mm swa

Does the consumer need 100A? (our local DNO is fitting 80A cut-out fuses as standard now). Just wondering if 80A/16mm2 might be easier/cheaper and just as satisfactory.

if swa doesnt need rcd protection ?

Not unless it's TT or Zs is too high.

Any thing else to be aware of with this job and sub main

Overall Zs?

If PME, where's the main bonding connected? - if at the CU end then you might be forced into 3-core SWA or an additional G/Y.

- Andy.
 30 October 2013 06:00 PM
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goldenboy1818

Posts: 503
Joined: 22 February 2011

yes domestic. Good idea on 80amp that would be ample anyway. Main bonds I would run back to consumer unit. And was thinking of using 25mm 3 core armour anyway. Not sure how to get armour from meter box to loft as its a bungalow. Cavity would be ideal but....
 30 October 2013 07:06 PM
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daveparry1

Posts: 6330
Joined: 04 July 2007

Can't see anything wrong with using the cavity myself GB.
Also, hope you don't mind me hijacking your thread but I have a question for Andy! Andy is it ok to use an 80amp switched fuse when the suppliers fuse is 80 amp or should we consider discrimination issues?

Dave.
 30 October 2013 08:48 PM
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OMS

Posts: 19857
Joined: 23 March 2004

There is no discrimination issue - either fuse operating results in the consumer being off supply.

In the event of a fault, it doesn't matter if either or both operate, you'll still have no supply beyond the most downstream device.

Having an 80A cut out fuse and an 80A sub main fuse is fine provided the sub main is designed for 80A

Regards

OMS

-------------------------
Failure is always an option
 30 October 2013 09:31 PM
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daveparry1

Posts: 6330
Joined: 04 July 2007

Thanks OMS, the sub-main is 35mm swa, the customer (friends of mine, (aren't they always in this sort of situation!) keeps wanting me to hang more and more on it and I think the 60 amp re-wireable switched fuse in the house, (on separate phase) will give up soon, I suppose I'll have to change to an 80 amp cartridge fuse unit. This is a separate building from the main house though so it's no too big a deal if it all goes off!

Dave.
 30 October 2013 10:11 PM
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Zs

Posts: 3010
Joined: 20 July 2006

Goldenboy, you have a pm from Zs.
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