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Topic Title: Adding switch fuse
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Created On: 24 August 2013 11:10 PM
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 24 August 2013 11:10 PM
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clarke24

Posts: 25
Joined: 18 May 2006

Hi I want to add a supply to my garage but there's no room in the cu. what I want to do is split the supply to the existing cu using Henley block then add in a switch fuse with a fuse rating of 60a. My question is can the dp isolator of the switch fuse be 80amp if the dno fuse is 100amp or will it have to be 100amp. I think it does but I wanted a second opinion.
 24 August 2013 11:15 PM
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peteTLM

Posts: 3084
Joined: 31 March 2005

What do you plan putting after the switchfuse going towards the shed?

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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 25 August 2013 12:37 AM
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alancapon

Posts: 5700
Joined: 27 December 2005

If you look at the "making current", the "breaking current" and the "operational current" for your proposed switch-fuse, then I am sure that will give you the answer to your question.

Regards,

Alan.
 25 August 2013 08:00 AM
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aligarjon

Posts: 2735
Joined: 09 September 2005

Blimey what are you running out there. If you need that sort of loading you will probably need a supply upgrade. I suspect you may just need a small consumer unit with a suitably sized circuit breaker depending on what your requirements are. If this is the case it may be a good idea to fit an rcd in it or get one with an rcd main switch if it only supplies the garage. The tails coming from your Henley block and size of the rcd are dependant on the proposed load in the garage rather than the supply fuse. In most cases a 40amp/30m/A rcd mainswitch would suit a domestic garage application.


Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 25 August 2013 09:36 AM
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clarke24

Posts: 25
Joined: 18 May 2006

It's supplying a 10mm swa cable to a cu in the garage. I put 80amp but I meant 60amp, so because the isolator would only have to switch what the 60amp fuse would allow it doesn't have to be a 100amp isolator?
 25 August 2013 10:13 AM
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daveparry1

Posts: 5889
Joined: 04 July 2007

That's correct, it's the load you'll be putting through it that's important, not the size of the main fuse. Depending on what you'll be running i'd have thought a 40 amp switched fuse would be adequate, or as I think Gary suggests a 40 amp rcbo which will give you rcd protection in the garage, unless you plan to rcd at the garage end,

Dave.
 25 August 2013 04:22 PM
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clarke24

Posts: 25
Joined: 18 May 2006

Thanks guys.
 27 August 2013 11:11 AM
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AJJewsbury

Posts: 10964
Joined: 13 August 2003

I'd stick with a 60A fuse - much better discrimination with the garage MCBs that way.
- Andy.
 27 August 2013 11:36 PM
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weirdbeard

Posts: 1373
Joined: 26 September 2011

Originally posted by: clarke24

Hi I want to add a supply to my garage but there's no room in the cu. what I want to do is split the supply to the existing cu using Henley block then add in a switch fuse with a fuse rating of 60a. My question is can the dp isolator of the switch fuse be 80amp if the dno fuse is 100amp or will it have to be 100amp. I think it does but I wanted a second opinion.


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