Fused spurs

[JohnD]

In my opinion the potential issue ( Although not in your case ) with adding two spur cables from a ring final circuits socket ,and connecting double sockets to each spur cable ,is the donor sockets ability to cope with the combined potential loads. If I recall correctly most are rated 16 to 20 amps.
Would be interested to know others opinions.

When you take a spur off a socket, the spur load does not pass through the socket. The connection is in the terminals. In one wire and out the other.

 

[JohnW2]

In my opinion the potential issue ( Although not in your case ) with adding two spur cables from a ring final circuits socket ,and connecting double sockets to each spur cable ,is the donor sockets ability to cope with the combined potential loads. If I recall correctly most are rated 16 to 20 amps.

Eh?

What about a 32A radial socket, in which the total current drawn by all the other sockets goes through the conductors in the terminals of the first socket?

Kind Regards, John

 

[winston1]

In my opinion the potential issue ( Although not in your case ) with adding two spur cables from a ring final circuits socket ,and connecting double sockets to each spur cable ,is the donor sockets ability to cope with the combined potential loads. If I recall correctly most are rated 16 to 20 amps.
Would be interested to know others opinions.

The donor socket would not be taking the load. Possibly the terminals may take some of it but most would be the contact between the cables.

JohnD beat me to it.

 

[terryplumb]

When you take a spur off a socket, the spur load does not pass through the socket. The connection is in the terminals. In one wire and out the other.

It's the donor sockets terminals that I refer to John

 

[JohnD]

The terminals just squash the wires together. Contact area is large. The terminals are rated to at least 32A

 

[JohnW2]

It's the donor sockets terminals that I refer to John

Indeed - but see my post #17. If (as you seemed to be suggesting) the terminals of a socket could not cope with more than 16-20A flowing through the conductors connected to them, then neither 32A ring finals nor 32A radials would be 'safe'.

Kind Regards, John

 

[terryplumb]

No, if you do that the new socket would only have 3amps available.

Connected to the supply terminals Winston. Would be limited by the first FCU at 13amp

 

[sparkwright]

No, if you do that the new socket would only have 3 amps available.



Ignorance.

There is no rule saying you can't have more spurs than ring sockets. It is possible to have a ring round the loft with every socket dropped down as a spur.

Again, the op IS on the right lines - until recent years, most textbooks would tell you that number of spurs could not exceed the number of sockets directly on the ring.

The op seems to have a good understanding of DIY electrics, I don't know why you persist in calling him ignorant.

 

[JohnW2]

- until recent years, most textbooks would tell you that number of spurs could not exceed the number of sockets directly on the ring.

You can probably forget the 'until recently' biut, since even the current version of the OSG says:

That seems to make absolutely no electrical sense - and (in my opinion) to add the distinction between fused an unfused spurs just adds insult to that injury!

Kind Regards, John

 

[EFLImpudence]

Again, the op IS on the right lines - until recent years, most textbooks would tell you that number of spurs could not exceed the number of sockets directly on the ring.

Not questioning the fact the they did, but what possible reason could there be for telling you that?

Have they never seen a bungalow with NO sockets on the ring?

The op seems to have a good understanding of DIY electrics, I don't know why you persist in calling him ignorant.

I think Winston was referring to the people who wrote the stupid 'rule'; not the OP.

 

[winston1]

I don't know why you persist in calling him ignorant.

I'm not. I am calling the people who are writing wrong advice ignorant.

 

[sparkwright]

I'm not. I am calling the people who are writing wrong advice ignorant.

Ah I see what you mean.

Apologies, apologies, apologies.

 

[AndyPRK]

I think what they are trying to avoid it taking many spurs from one point.
If you spured 2 double sockets from the same point, you could in therory draw 40A from an unbalanced end of a ring. Just as well I haven't done that

But as the OP has an alarm, at less than 1A draw and something else, it's not an issue for them

 

[JohnW2]

I think what they are trying to avoid it taking many spurs from one point. If you spured 2 double sockets from the same point, you could in therory draw 40A from an unbalanced end of a ring. Just as well I haven't done that

I'm sure that nothing disastrous would happen even if you did!

However, the situation you describe could just as easily arise if one has two or more sockets very close together (ON the ring) near one end of the ring, so there's nothing special about spurs.

The regs already require a ring final circuit to be designed so as to minimise the risk of any part of the cable being 'overloaded for long periods of time' - so that requires the judgement and discretion of the designer just as much in terms of the location of sockets close to the end of the ring as it does to multiple spurs originating from a single point close to the end of a ring.

Once one is away from the ends of the ring, there are no issues in relation to either 'close together sockets' or 'multiple spurs originating from the same point'.

The main issue as regards multiple sours with a common origin is the capacity of socket (or even JB) terminals since even two spurs (4 conductors in each terminal) can be difficult, and more than two probably usually impossible.

Kind Regards, John

 

[333rocky333]

You can probably forget the 'until recently' biut, since even the current version of the OSG says:

View attachment 181069

That seems to make absolutely no electrical sense - and (in my opinion) to add the distinction between fused an unfused spurs just adds insult to that injury!

Kind Regards, John

Surely there referring to the drawing in appendix 15, and there "Fused" is referring to unlimited if the fuse is in the first spurred point or "unfused" as in spurred direct of the ring, they must not exceed the total number on the ring , but as you know still limited to 1 single or double at each joint.

Ruling out Winstons suggestion of a ring round the loft with no sockets and all sockets spurred off it.