Comments, please. I've read history in this group, consulted the Wiring Regs
and the OSG. I
can find nothing that precludes me from implementing my preferred design for a
power feed to the
I intend to take feed from kitchen ring main through a DP switch and a 13A fused
spur unit to a
4mm.sq SWA cable running to the shed. I intend to fit some RCD protected mains
sockets in the
shed, and take a feed through a 5A fused plate for lighting. The SWA cable is 3
core so I get a
4mm earth as well as the armour. The cable is burried at 400mm in an old metal
pipe and plastic
tape above. The house istallation is PME and I have test equipment to check
impedence etc once the job is done. I will rely on the earth from the house
(rather than treat
the shed as a TT, float the earth at the shed end and drop an electrode). The
load in the shed
is minimal, including the use of power tools and garden tools and while I may
install a small
freezer I will accept a trip risk.
I have considerable DIY electrical experience and I would not as a matter of
take a spur off the kitchen ring but I have no spare ways on the CU whuch is
towards the front
of the house which has concrete floors and there's no viable cable route. My
possibility would be a feed from the Cooker Unit (this is a serious possibility
if we put in a
gas cooker when the kitchen is refurbed!).
Can anyone point me to any breach of regs or problems in the above design - I
know it's not
ideal, but it is a considered design.
Wouldn't it be easier to take a two way consumer unit from your meter or
doubled up with the mains switch in the existing CU, and then run the SWA
supply from that. You say you have three cores in the SWA, so it would
allow for the lighting and power to be drawn from the red and yellow cores
and share the black as a neutral. You'll still have the armour as a decent
earth to a metal clad junction box in the shed, or spike it at the shed end
and reinforce the bonding to ground from there as it wouldn't hurt to give
any extra. This way it is on its own and will not effect the house supply
if a fault is detected in the shed.
Outgoing mail is certified Virus Free.
Rather than use RCD protected sockets in the shed, I'd use an RCD fused
connection unit instead of the DP switch/fused connection unit you intend.
This will mean that the cable run and lighting is also RCD protected (making
low earth loop impedence a belt and braces approach, rather than critical)
and be cheaper if you are installing more than one socket.
I forgot. If the shed has any structural metalwork or metal services, such
as plumbing of any kind, they will need to be main bonded back to the main
earthing terminal near the consumer unit using an unbroken cable of very
large cross sectional area. As you say the consumer unit is inaccessible,
this would preclude your technique and require a TT installation.
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