Spur off spur

[danny199]

Hi,

Just need to check something. Sparky installed two new plug sockets. To do this, cut into the main ring, put a junction box in, one cable out to socket. Then from there connected one more plug. I understand to spur off a spur you should use a fuse between them?

 

[Strima]

The spur should be fused down before the first socket if there’s multiple sockets on the spur.

 

[Baddegg]

So easy to just extend the ring anyway in that instance?.....

 

[Spoon]

As @Strima says.

 

[StephenRowley]

Are you sure he's not just extended the ring?

 

[Kidsolo]

Help an Aussie understand.
The fuse connected to the spur, where is that physically situated in the installation? alongside the outlet, back in the switchboard, or somewhere else?
and do you guys still use fuses, or is that your name for a breaker?

A ring circuit has two actives in the bottom of the main breaker and two neutrals in the neutral link?

 

[Pete999]

Help an Aussie understand.
The fuse connected to the spur, where is that physically situated in the installation? alongside the outlet, back in the switchboard, or somewhere else?
and do you guys still use fuses, or is that your name for a breaker?

A ring circuit has two actives in the bottom of the main breaker and two neutrals in the neutral link?

To spur off a RFC with multiple outlets, you must have a Fused spur as the first outlet then your socket outlets as described in the diagram posted earlier, the fuse in question will be a cartridge fuse housed in the fused spur unit max size 13 Amps, hence the max allowed in the socket outlets you feed from that Fused spur unit will be limited to 13 Amps, the RFC may still be protected via a MCB at the CU, does the existing RFC have RCD protection? Hope that makes sense.

 

[Kidsolo]

Hope that makes sense.

It makes sense (not that I think it is a great way of wiring a circuit). I know the logistics of it, I was more wanting the know the physical location of the fuse. So it is embedded in the socket?
Why are you still using fuses?

 

[Pete999]

It makes sense (not that I think it is a great way of wiring a circuit). I know the logistics of it, I was more wanting the know the physical location of the fuse. So it is embedded in the socket?
Why are you still using fuses?

No Mate not imbedded in the socket The switched fused spur unit is a separate unit, roughly the same size as a socket, used for fusing down when you are connecting lower load, difficult to explain to a non Brit, the fi/use is of the type used in 13Amp UK plug tops, google "switched fused unit" it may explain "a picture is worth a thousand words" as they say

switched fused spur connection unit - Bing

Intelligent search from Bing makes it easier to quickly find what you’re looking for and rewards you.

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[DPG]

It makes sense (not that I think it is a great way of wiring a circuit). I know the logistics of it, I was more wanting the know the physical location of the fuse. So it is embedded in the socket?
Why are you still using fuses?

We use both fuses and circuit breakers. Any new consumer unit will be populated with MCBs or RCBOs. Appliance plugs and fused connection units will have fuses.

Fuses are also useful when you need discrimination between upstream/downstream devices.

The fuse is not embedded in the socket, it is held in a faceplate accessory which has the same dimensions as a standard 13A socket outlet.

 

[fairlight]

Hi,

Just need to check something. Sparky installed two new plug sockets. To do this, cut into the main ring, put a junction box in, one cable out to socket. Then from there connected one more plug. I understand to spur off a spur you should use a fuse between them?

Were the sockets singles or doubles? Whilst not technically correct it would be acceptable in practice if both sockets were singles, as this would be no different to a double socket on a spur.

 

[Pete999]

Were the sockets singles or doubles? Whilst not technically correct it would be acceptable in practice if both sockets were singles, as this would be no different to a double socket on a spur.

A spur is a double socket or a single, so taking two singles us wrong in my book

 

[westward10]

Were the sockets singles or doubles? Whilst not technically correct it would be acceptable in practice if both sockets were singles, as this would be no different to a double socket on a spur.

No it isn't technically correct at all. I understand your theory but nevertheless it is incorrect advice.

 

[fairlight]

No it isn't technically correct at all. I understand your theory but nevertheless it is incorrect advice.

I said it is not technically correct. But if I was doing an EICR two doubles on a spur would be a code 2, two singles would be a code 3. If two singles were butted together they would look like a double, a couple of meters of cable between and suddenly it's a different ball game. Not saying it's compliant but in practice there is no difference whatsoever, the regulations are not statutory and deviation can be justified where equivalent safety is achieved.

 

[westward10]

You said not technically correct but acceptable. A two gang socket is type tested with a load of 20A (14A and 6A) across the outlets and whilst in practice this may not be the case it is fact. Based on this a two gang socket will draw no more than 20A, argue this with British Standards. Two one gang sockets have the potential to draw 26A. To apply a departure you could not guarantee a lesser standard of safety is provided by using two one gang sockets.

 

[StephenRowley]

Why are you still using fuses?

Because they we've got a 32amp ring main. And appliances with wiring that are designed to handle 13amps max(often less) so we stick a fuse in the plug to protect the appliance, saves on copper.

 

[fairlight]

You said not technically correct but acceptable. A two gang socket is type tested with a load of 20A (14A and 6A) across the outlets and whilst in practice this may not be the case it is fact. Based on this a two gang socket will draw no more than 20A, argue this with British Standards. Two one gang sockets have the potential to draw 26A. To apply a departure you could not guarantee a lesser standard of safety is provided by using two one gang sockets.

'Based on this a two gang socket will draw no more than 20a'!!….. Does it have a current limiter then?? A twin socket can, and will, have two 3kw 13a appliances plugged into it just the same as two singles because the plug fits both. The type testing is based on average loadings likely to be applied in average circumstances, the same average circumstances apply whether it is a twin or two singles. British Standards can say what they want, Joe Public will never ever be heard to say. " Ah, two 3kw appliances I need to use, I cant plug those into a twin because it'll only take 20a, I'd better find two separate singles to plug them into".

 

[westward10]

As I said in practice this may not be the case.

 

[sinewove]

As I said in practice this may not be the case.

I believe MK claim their twin sockets are good for 2x13A loads

 

[Kidsolo]

used for fusing down when you are connecting lower load

Sure, you are down sizing the fuse so that socket alone can't exceed 13 amps, while the rest of the circuit can. But one needs to ask "why"? Why not just use the protection set aside for the ring circuit? It is still part of the main circuit as an overall load, so why does a stray socket suddenly need it's own fuse?
and why a ring circuit? sure, it splits the load, but why not just make 2 separate circuits? you have already run the cable back to the switchboard. That way you have two separate circuits, both sharing the load of all the sockets... but you have the added advantage of only tripping one circuit at a time, instead of losing power on everything.