On 26/09/2020 00:27, Fredxx wrote:
On 24/09/2020 12:18:05, wrote:
On Monday, 21 September 2020 04:07:20 UTC+1, FredxxÂ* wrote:
On 21/09/2020 04:02:32, ARW wrote:
On 21/09/2020 00:08, Fredxx wrote:
On 20/09/2020 09:11:41, Jeff Layman wrote:
Fortunately not mine!

A friend just told me "I have just replaced a single electric socket
in our lounge with a switched double. In order to stop the supply, I
had to switch off two trip switches at the same time." That didn't
sound right, or safe.

DIYWiki notes: at
(http://wiki.diyfaq.org.uk/index.php/Ring_circuit):
"The ring circuit cable starts at the consumer unit (fusebox]),
visits
each socket in turn, and then returns to the consumer unit. The 2
cable
ends at the CU are connected together in all modern rings, and
supplied
by one fuse or MCB."

That confirms there should be one MCB, but I note the use of "...in
all modern rings...". Does that mean there might have been two fuses
or MCBs in early rings? I think his house was built around 1980.

I can see the logic, where the two MCBs are each rated for 2.5mm cable
which will allow more current be safely pulled along the ring.

I wonder if it will catch on?






Obviously you would need a common RCD.

Actually you do not as there will be no imbalance between live and
neutral.

Any imbalance (leakage to earth) would be shared between the two RCDs,
assuming they are identical. So the residual current would be close to
twice the expected value before one tripped. The other would follow
immediately.

Any slightly high R joint would result in imbalance & trip the RCDs.

I have to say was my thought. Worst case scenario would be live fed
through RCD and neutral fed through the other RCD.

Both would see an imbalance equal to the current drawn by the load.

Thanks to John's input I can now find the diagram I drew.

http://i428.photobucket.com/albums/q...o2020/ring.jpg

The argument was about if the RCDs would trip in a normally functioning
circuit.

Add a high resistance on one of the lines and there will be a trip.

--
Adam