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RE: LD10's and MCB's
- To: <ukha_d@xxxxxxx>
- Subject: RE: LD10's and MCB's
- From: "James Hoye" <james.hoye@xxxxxxx>
- Date: Thu, 30 Aug 2001 15:12:52 +0100
- Delivered-to: rich@xxxxxxx
- Delivered-to: mailing list ukha_d@xxxxxxx
- Mailing-list: list ukha_d@xxxxxxx; contact
ukha_d-owner@xxxxxxx
- Reply-to: ukha_d@xxxxxxx
> I was thinking of putting in say 3 30amp rings (these would be very
> short, running from my fuse board to the board containing the LD10s)
for
> lighting (one for each floor) and running all LD10's into their
> respective 30amp MCB, thus saving on 15 or so 5ampers... good idea?
No problem with the first bit (running 3 x 32A rings) - but the proviso is
that the cable is protected at the main CU with a suitable MCB/fuse. If
you
want 32/30A then you must use 2 lengths of 2.5mm^2 twin and earth (T&E)
OR 1
length of 4mm^2 T&E.
At the LD10 distribution board, I would be very wary of running the LD10s
straight into a 32A MCB - even though each is fused (at 5A?) in case the
LD10 terminals can't handle 32A (would pose a fire hazard if there was a
short circuit fault insufficient to trip the 32A MCB, but too much for the
LD10s to handle. Rather I would use an additional CU with several (say 3)
5A MCBs then feeding a bank of LD10s (say 5). That way you'd only need 3
MCBs (and not 15) - but you would need an additional CU!
The main point to remember is that a MCB or fuse only exists to protect the
wiring from over current caused by a fault. When going down a cable size
(eg. 4mm to 1.5mm) you must install a suitable protection device between
them. Going up in cable size poses no problem, PROVIDED that the lower
rated cable is adequately protected.
Lost? Get hold of
http://www.amazon.co.uk/exec/obidos/ASIN/0852969295/markmccall/
- be safe
and not sorry.
James H
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