DIY Doctor

Old ring main ???

Postby dbdunce » Wed Feb 10, 2010 3:42 pm

I am trying to understand my home electrical power circuit (house built 1960's)
Is there a quick way of finding out if the power sockets are 'Ring' or 'Radial and/or spur' - short of taking each socket out to look at the wiring.
Even then two lots of wire could mean either ring or it could mean a carry over to next socket.
The fuse box is the old style cartridge fuse with just one fuse for any particular circuit. If I had ring main would there have been a fuse on EACH of the 2 lines of any one circuit or would the two lines be connected to the same fuse?
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Simply Build It

Postby sparx » Thu Feb 11, 2010 5:24 pm

for the purpose of your understanding, not to encourage 'dabbling':

A ring circuit starts and finishes at the same 30A fuse holder.

Its Neutral should start and finish at the same term. in the N bus-bar,
in the corresponding number /position as the Lives ie, L in fuse 2, N in term. 2 say.

likewise the earths (Circuit Protective Conductors). in term 2 of earth Bus-bar.

To determine if a circuit is a ring & if a particular socket is indeed on the ring rather than a double spur is more difficult and cannot be determined visually, but requires at least a test lamp (2 probe type, not neon test screwdriver!) plus the competance to use it safely.

This test requires the circuit to be dead, a suspect socket to be disconnected, the ends put in seperate connector blocks, the power restoring and each live tested. If both live then should be on ring, if only one live then is a double spur (not allowed by regs.).
Then power off & reconnect socket.

A way of doing checks which is ok for one unknown socket but very time consuming if all being tested!

Leckies can check insitu by plugging in expensive 'loop impedance' meter,
with circuit live, or using a low reading ohmmeter with dead circuit, this does need careful interpretation though.

regards Sparx
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Postby dbdunce » Thu Feb 11, 2010 6:05 pm

Thanks Sparx.
I was hoping for an easy way but I will follow your method socket by socket.
Since there is only one wire per circuit going back to the fuse box I'm sure it must be non ring. There seem to be quite a lot of junction boxes under the floor boards going every which way so it looks like a mixture of radial and serial and spur. Bit of a nightmare really!!
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