You are reading a single comment by @moth and its replies.
Click here to read the full conversation.
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
@moth
If the purpose of fuses is to protect the cables from overheating when too much current is drawn through any of their conductors, then ring mains are a bad idea.
A straight run cable can be protected with a single fuse on the live.
With a single fused ring, the fuse will be rated higher than the cable connected to it because the load is assumed to be shared evenly between the two routes round the ring.
As long as everything is properly connected, the positive temperature dependence of resistivity will get you close enough to that assumption, but the connections in a ring main can fail without being noticed. If the ring is cut, all the sockets can still work but the cable will be inadequately fused.
So how about two separate fuses, one on each end of the live? Now you have to blow two fuses before the cable is neutralised. And what if the live ring is complete but the neutral conductor is cut?
So you need a circuit breaker that separately monitors the current through both the lives and both the neutrals and isolates all of them if it's tripped by any. And an RCD. In case it's the earth ring that's cut...
What could cut the ring? Someone adding sockets to it and failing to make all the connections, just enough to make the socket live. Or maybe the connections are made, but some of them just quitely corrode a bit and go high-resitance. You could reduce the risk of that by connecting the sockets in a way that doesn't physically cut the conductors. I have no idea if sockets are designed to make that easy.
Or you could just not use ring mains.
(i am not an electrician)