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Topic Title: Twinning from main switch
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Created On: 30 April 2013 04:11 PM
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 30 April 2013 04:11 PM
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Ses2010

Posts: 2
Joined: 27 April 2013

Just carried out an inspection at factory

They have a 10mm swa from a 63amp mcb feeding another db
Off the incoming side of the second db 100amp main switch they have took another 10mm to feed a 63amp switchfuse which then feeds two aircon units via another 2 32amp switchfuses

Apart from reg 314 division of installation i can find reg that says you cant come off a main switch but it doesnt seem correct
 30 April 2013 04:43 PM
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AJJewsbury

Posts: 11766
Joined: 13 August 2003

They have a 10mm swa from a 63amp mcb feeding another db
Off the incoming side of the second db 100amp main switch they have took another 10mm to feed a 63amp switchfuse which then feeds two aircon units via another 2 32amp switchfuses

So the 63A switchfuse is probably redundant (with the 63A MCB upstream) so what you effectively have is the two aircon unit 32A fuses and all the outgoing ways of the second DB all fed from the same supply - so the same overall effect as if the two aircon units were fed direct from the 2nd DB (if there had been enough spare ways).

If there's no reason to object had the aircon units been fed from the same DB as the rest of the circuits, I don't see any reason to object in principle to the setup you've found.

The only problem I can think of is if the terminals aren't really able to accommodate the extra cables properly - e..g. if strands had been snipped or there was any obvious strain (probably unlikely with 2x10mm2 as the terminals are probably good for 25 or 35mm2).

Labelling should overcome any confusion about what switches off (isolates) what, if there's any doubt.

- Andy.
 30 April 2013 04:58 PM
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Ses2010

Posts: 2
Joined: 27 April 2013

Great thanks for your help
 01 May 2013 11:55 AM
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joepostle

Posts: 73
Joined: 14 September 2011

Just thinking out loud but a 60a supply (in 10mm) feeding 2x daisy-chained DBs and 2x 32a S/Fs feeding 2x A/Cs doesn't sound though there's much diversity. Presumably the 32a S/Fs are rated suitably for the intended load, therefore potentially 50% of the supply used. As I say, just thinking out loud!
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