"Mark" wrote in message
...
On Mon, 18 Dec 2006 19:42:09 -0000, "Sparks"
wrote:
Thanks for your reply.
"Mark" wrote in message
. ..
Some time ago I fitted a new socket outlet in my son's bedroom. I had
no desire to go into the wall and hook into the existing ring main so
I decided to tap in somewhere else. Basically I tapped into the
immersion heater supply in the airing cupboard, (fused 30amp at the
consumer unit).
What size cable is this circuit using - 4mm or more I hope, if it is 2.5mm
you need to replace the 30A MCB with a 20A one, unless the immersion is on
it's own 2.5mm ring.
My mistake, the immersion is on a 16A mcb, it's the electric cooker
supply that's on a 30amp mcb.
If you have an immersion, I hope this is connected with an FCU, fused at
13A
(Unless you have the unlikely scenario of an immersion heater greater than
3KW)
Yes the immersion has its own FCU in the airing cupboard with a 13amp
fuse
Then I went through a 13amp fused spur, then up into
the attic, and then down into the bedroom using mini trunking, and
finally connected an RCD protected double socket. Everything fine.
Possibly fine, if the immersion heater cable is 4mm (or more) or on a
2.5mm
ring.
Now I need to do the same in my daughter's room. My question is, if I
wire in parallel from the feed to the socket in my son's room do I
need to use another RCD protected socket? Or will the RCD in my son's
room provide protection for a regular parallel socket.
Unless the socket in your son's room has a dedicated RCD protected output,
and you use this, you need another RCD socket, or just replace the fused
spur with one of these.
http://www.tlc-direct.co.uk/Products/CM4904.html (Then any further
additions
will be protected)
Thanks for the recommendation
If you just connect a normal socket to the same terminals the existing
socket is being supplied with, it will not be protected.
Why not? Isn't the RCD measuring earth leakage irrespective as to
whether something is plugged in 'in front of it' or 'behind it'?
No,
If that were the case, your whole house and all the people on the same phase
as you would be protected by your RCD socket.
The socket is measuring the differance in current at it's output, it can't
control what goes into it. - are you sure you should be messing with this,
no offence, but you don't sound like you should be.
Safety is paramount of course but I don't want to spend 20 odd quid on
another RCD socket if I don't need to.
Incidentally the sockets are only for hi-fi/TV so I doubt the combined
load will ever exceed 5 amps.
This is irrelevant, you are providing a 13A socket, it needs to be able to
support this load - someone may plug in a heater at some point.
Yes, and if the load is over 13amps the fuse in the spur blows, I
don't see a problem here as long as the cable itself is correctly
rated?
There may be some regulations about not being able to apply diversity to
circuits with fixed loads on (The heater in this case) but I don't know, I
wouldn't do it this way myself, unless the heater was decommisioned.
With your immersian heater on, assuming it is 3KW, you only have 3A (700w)
of spare capacity before the MCB is at it's marked limit - You can probably
uprate this MCB to a 20A, but this still only allows 7A with all at full
chat.
....and it doesn't sound like you should be poking about in the consumer unit
anyway!
The ideal way to do it is to either tap into an existing ring (Only one
double socet per tapping, unless you fit a spur in-between, then you can fit
as manu as you like downstream) or run a new circuit from the consumer unit.
Part P will apply.
Sparks...
(Not an electrician)