On 26/09/2020 20:10, wrote:
On Friday, 25 September 2020 15:24:49 UTC+1, Max Demian wrote:
On 24/09/2020 21:48, tabbypurr wrote:
On Thursday, 24 September 2020 17:24:20 UTC+1, Max Demian
wrote:
On 24/09/2020 12:15, tabbypurr wrote:
On Sunday, 20 September 2020 10:54:40 UTC+1,
wrote:
On Sunday, 20 September 2020 10:48:07 UTC+1, Chris Green
wrote:

Our house (as in the house I grew up in, back in the
1950s) had a very early ring circuit as it was built in
1949 or thereabouts. It definitely had fuses at each end
of the ring. Whether that was as it should have been or
just how the electrician (my father I think) thought it
should be I don't know.

When rings were first introduced, people used to make them
from 2 15A radial circuits joined together.

I don't know how officially-sanctioned that was or for how
long.

It was part of the original rationale for the design.

Was each circuit fused for the whole ring, or half?

2x 15A fuses running a 30A ring. The point was one could add
unlimited extra sockets by joining 2x existing 15A socket
circuits into a ring. It was an ingenious solution combining cost
cutting with safety improvement.

What if you plugged two 3kW fires into sockets near one of the
fuses?

Firstly that's unlikely in practice, and very unlikely for them to
run for long.

wouldn't it blow, or at least overheat the nearest fuse? A proper
ring main would cope easily with a single 32A fuse.

The cable would run hot, but not hot enough to be a hazard. 15A
BS1361 fuses trip in around 20 seconds at 30A,

They might - but that is a bit optimistic - 5 mins sound more likely.

(and in a CU of that era a BS3036 rewireable would be more likely than a
cartridge fuse I would have thought)

so it probably would.
The user wouldn't notice until the other fuse tripped another 20s or
so later. Some users might then fit 30A fuse wire or a suitable nail,
enabling the thing to run indefinitely. It would.


NT



--
Cheers,

John.

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