2 spurs coming from the same socket - NOT a spur from a spur!

[electrician4u]

Hello all..

I have recently added a spur for a customer and it got me thinking again about how many spurs could I actually take from the same socket!

The only socket I could use to take the spur from was on the ring and was already feeding a spur. Now I could have extended the ring but after a small amount of investigation I found that the existing spur was to a single socket hidden behind kitchen cupboards and never used so I disconnected and then fitted my spur.

It did make me think what was wrong with adding 2 spurs to the same socket though. The new socket was a crabtree and could easily accomadate 4 2.5mm conductors.

A double socket that is feeding a double socket spur has the (unlikely) potential to take 26A from the spur plus another 26A from whatever is plugged into it (therfore a maximum of 32A could flow through that one socket). By adding another spur to the socket the maximum it could take is not changed (still 32A).

I think the answer is that although possible its not a good idea to push the limit of a socket and by adding another spur I am pushing it closer to the limit of 32A more frequently which would be bad practice and unecessary as you can just extend the ring, but I'm thinking about it and need answers from the experienced chaps as otherwise I shall become frustrated!!!!

when did 26+26 start equalling 32? it's 52

 

[markc123]

when did 26+26 start equalling 32? it's 52

Edit.

 

[Des 56]

when did 26+26 start equalling 32? it's 52

Yes indeed, 52 is what I made it ,mind you the double digit adding was a bit taxing for me

I think he had in mind 32 amp circuit max rating

 

[markc123]

Mis-read the OP....can see how you've got the 52 now.

I just presumed in my brain the 32A rating.

Not to worry ladies and gents.

 

[electrician4u]

A 32A mcb doesn't act as a current limiting device! and btw, 52A would take about 10 minutes to trip a B type mcb and likely won't trip at all until about 47A being drawn, so the Regs say anyway.
don't underestimate the general publics' ability to abuse sockets. was called out to an office some time ago as they said their sockets were tripping to find a fan heater connected next to everyone's desk.they had 8 2kW heaters connected drawing 66A and the mcb still hung on for a few minutes after re-setting! in the last Regs you could spur off a spur but that's been changed obviously.

 

[DPG]

A 32A mcb doesn't act as a current limiting device! and btw, 52A would take about 10 minutes to trip a B type mcb and likely won't trip at all until about 47A being drawn, so the Regs say anyway.
don't underestimate the general publics' ability to abuse sockets. was called out to an office some time ago as they said their sockets were tripping to find a fan heater connected next to everyone's desk.they had 8 2kW heaters connected drawing 66A and the mcb still hung on for a few minutes after re-setting! in the last Regs you could spur off a spur but that's been changed obviously.

You could spur off a spur in the last regs ??? Daz

 

[Deleted member 9648]

A 32A mcb doesn't act as a current limiting device! and btw, 52A would take about 10 minutes to trip a B type mcb and likely won't trip at all until about 47A being drawn, so the Regs say anyway.
don't underestimate the general publics' ability to abuse sockets. was called out to an office some time ago as they said their sockets were tripping to find a fan heater connected next to everyone's desk.they had 8 2kW heaters connected drawing 66A and the mcb still hung on for a few minutes after re-setting! in the last Regs you could spur off a spur but that's been changed obviously.

You could spur off a spur in the last regs ??? Daz

maybe the last regs book he possessed was the 13th?

 

[markc123]

Haha, maybe wirepuller.

That's a interesting question to be fair. Whats the oldest copy of the regs anyone holds? Or do you just bin them?

I've got a shyte load of books in the attic...im a hoarder when it comes to electrical information and publications.

 

[Deleted member 9648]

Started with the 14th and always regretted binning it,would be an interesting read now.

(note to self...GET OUT MORE)

 

[Golden_Boy]

As there is no MINIMUM distance that sockets can be spaced on a rfc.then in practice you could have 2 literally next to one another and have one spur from each of them. 3 or 4 inches of cable in between. Satisfies the regs but in practice is exactly the same as having 2 spurs from one socket, Thinking about it it is worse as there are now 8 outlets available...

 

[Aindowsimon]

That's true about the whole RFC they are only 2 legs unlimited skts within permitted square meterage and one sper permitted to each , if those skts are deemed to be likely to supply a heafty loading surley the installation design is at fault and not RFC witch 9/10 will serve occupants more than adequately

 

[electrician4u]

You could spur off a spur in the last regs ??? Daz

used to be common practise

 

[scammell man]

BS7671 433.1.103 and appendix 15 page 425 (you have got one of these, haven't you?).

very self explanatory. Unfused spur = 1 cable + 1 single gang or 1 two gang socket.
Doesn't say you can't have 2 spurs from the same point. Selection and erection criteria will apply though.
If extending the ring be very careful you don't create a figure of 8!

 

[electrician4u]

BS7671 433.1.103 and appendix 15 page 425 (you have got one of these, haven't you?).

very self explanatory. Unfused spur = 1 cable + 1 single gang or 1 two gang socket.
Doesn't say you can't have 2 spurs from the same point. Selection and erection criteria will apply though.
If extending the ring be very careful you don't create a figure of 8!

doesn't seem very good practice though even if it is technically allowed.i've only ever come across it in BIY (bodge it yourself!) situations

 

[scammell man]

personally I think unfused spur in 2.5mm to a 2 gang is poor practice. Why not use 4mm?

 

[DPG]

used to be common practise

Not in the last regs though as the poster suggested. Daz

 

[telectrix]

personally I think unfused spur in 2.5mm to a 2 gang is poor practice. Why not use 4mm?

funny you should mention that. i was thinking along the same lines. it's like a reverse lollipop circuit. in effect the 4mm would give you a 32A capability on the spur, so theoretically you could add more than 1 outlet on the spur.

 

[scammell man]

[/QUOTE] in effect the 4mm would give you a 32A capability on the spur, so theoretically you could add more than 1 outlet on the spur.[/QUOTE]

Then you would be in departure from BS7671 and lots of onus on you to show equivalent safety. Agree this is possible though.

I work on 2x13 A load continuous, 4mm should be good provided installed correctly, i.e. no serious down ratting factors applied. Now totally safe and no chance of thermal overload. I do not like cable rated below breaker rating in ANY situation.

 

[gazj82]

I work on 2x13 A load continuous, 4mm should be good provided installed correctly, i.e. no serious down ratting factors applied. Now totally safe and no chance of thermal overload. I do not like cable rated below breaker rating in ANY situation.

In theory it is limited by the fuses in the plugs that will go in the socket. In practice this sort of doesn't work because of unfused doublers etc.

A good example of where fusing down after a reduction in cable size does work is the old busbar chamber method. Tap off in smaller cables and switch fuse after the reduction. Just because the fuse is not immediately before cable reduction does not mean it's not protected.

 

[jamminuk]

Doing an EICR on a property and came to the kitchen, when i dropped the sockets my jaw also dropped, no end to end on the ring, one socket had the following spurred off of it - 3 double sockets, extractor hood, cooker ignition which then also had another socket spurred off that to feed a washing machine!!!! dropped another socket as looking for other leg of the ring to find a socket fed in 1.5mm!!! The guy has just had his kitchen fitted, looks all lovely and nice on the surface but really bad underneith. This was done by a Romanian builder who has no clue re electrics. I told the guy this needs to be sorted asap, i suggested he'll need a few fcus for the various spurs but it'll mean breaking a tile or two to put them in, cant really put any sockets below as cupboards already fitted, then try to find the other leg and put links between to make a complete ring, cant see any other way of doing it other then putting it on a 20A radial but that's not an ideal solution in my mind really, any other ideas? I thought you could only spur once off a socket unless you put an fcu then you can have as many as you like, didn't think you could spur out of a socket as many times as you can fit the cables into the terminal, doesn't sound like the right thing to do even if not in regs.