Spur Problem

[Shaneyboy]

I have discovered that a double socket in my dinning room is a spur from a double socket in the kitchen. The double socket in the kitchen is itself a spur. Should I remove this, is it potentially dangerous?

Kind Regards.

 

[ban-all-sheds]

If you're sure they are spurred off a ring final, and that it's not a radial circuit, yes and yes.

Put a fused connection unit before the fist socket.

 

[Shaneyboy]

Thanks BAS, will remove it ASAP.

Kind Regards.

 

[riveralt]

If you're sure they are spurred off a ring final, and that it's not a radial circuit, yes and yes.

For the second yes, why do you consider it potentially dangerous?

 

[PrenticeBoyofDerry]

If it is a radial circuit then it should okay, if ring final circuit then a fused connect unit would need to be installed at the intersection of feed and first socket.

 

[ericmark]

It is all too easy to assume sockets are un-fused spurs from a 32A supply when there is a single cable feeding them. However in my kitchen there is a 13A socket which feed two more 13A sockets one in living room and other in room that did have the immersion heater when the house was built all three feed from a B16 MCB which was originally for the immersion heated nothing wrong with doing this. It was common to have a switch in kitchen to control immersion heater. It also could be fed with 4mm cable again if kitchen socket fed with 4mm then no problem taking an un-fused spur from it.

If sure they are feed from a 32A supply with 2.5mm cable then yes it is wrong and should have a FCU swapping the double socket box for a twin socket box and having a single socket with FCU in kitchen likely way forward.

As to botch with 13A plug feeding living room socket yes OK but in the main we do not use heavy stuff in the living room and if it were my house I would stick some tape across it and then modify just before we next decorate.

 

[ban-all-sheds]

For the second yes, why do you consider it potentially dangerous?

Two DSOs on a 2.5mm² cable?

 

[JohnW2]

For the second yes, why do you consider it potentially dangerous?

Two DSOs on a 2.5mm² cable?

Is there perhaps some linguistic pedanticism at work? ....

... The double socket in the kitchen is itself a spur. Should I remove this, is it potentially dangerous?

Riveralt may well haven taken your 'yes' to indicate that the kitchen socket was 'dangerous and therefore should be removed', whereas it's actually the dining room one (the spur from a spur which is the problem.

Kind Regards, John

 

[ban-all-sheds]

Ah - could be.

 

[ericmark]

Spur. A branch from a ring or radial final circuit.

Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

OK so how is a cable coming from a FCU called a spur? It forms it's own circuit as it has it's own over current device but yet we still call it a spur. To me it should be called a radial however this means to describe a spur really needs more than what is in the BS7671 specially where we are telling people without seeing the installation they should rip it out.

So the big question is fuse, MCB, or RCBO size that feeds the socket remember "Shaneyboy" calls it a spur not a un-fused spur and clearly not an electrician or would not be asking the question.

Being fair to BAS he does say "If you're sure they are spurred off a ring final, and that it's not a radial circuit" and did suggest adding a FCU not ripping it out, but reading question and answer it could well mean "Shaneyboy" intends to remove the kitchen socket not living room one and "JohnW2" has pointed this out with "Is there perhaps some linguistic pedanticism at work? ....".

The potential for any electrical installation to be dangerous is always present and we must assess the risk and decide if the risk is acceptable in a work situation we would lock off, remove tails or use some other method which would require a tool to be reversed but really in the home by the occupier a simple bit of tape is normally enough to remind occupants not to use a socket and to remove ASAP is not really required it only needs to be removed when next decorating. The danger is only there when it is used by high power equipment being there does not present a danger the danger only exists when being used.

 

[JohnW2]

Spur. A branch from a ring or radial final circuit.
Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

Those are, indeed, the BS7671 definitions, but IMO they are totally unsatisfactory. In particular, to say that a branch from a radial (with same cable CSA as the rest of the circuit) is a 'spur' is totally meaningless - if two 'branches' arise from one point in a radial (say, a socket), which is a continuation of the radial and which is the spur? That's daft!

OK so how is a cable coming from a FCU called a spur? It forms it's own circuit as it has it's own over current device but yet we still call it a spur.

Indeed. What you say is true in terms of the BS7671 definitions (and, as you know, creates a potential issue in relation to the new notification requirement {for a 'new circuit'} in England). If the FCU is connected to a ring circuit by a bit of single cable (rather than being wired-in as part of the ring), then the cable from ring to FCU would obviously qualify as 'a spur', both per BS7671 and 'common sense' definitions. To call the wiring downstream of the FCU as 'a spur' is, I suppose, just ('convenient') 'established jargon'.

The situation is obviously more straightforward with a ring final than a radial final circuit. It seems very reasonable to regard any single-cable emanation from the ring as being 'a spur' - and (despite the BS7671 definition of 'a circuit') that sensibly also apply downstream of any FCU in that 'single cable' circuit.

With radials, it's different. As above, if all cable is the same CSA, then any attempt to define a 'spur' is totally meaningless, and unhelpful. Personally, if there is a reduced-CSA branch of a radial (fed via an FCU if it feeds more than one socket), I would be inclined to call that a spur. That might actually suggest a more workable/useful definition of a spur, from either ring or radial circuit - one could define it as a single-cable reduced-CSA branch from a ring or radial final.

Kind Regards, John

 

[knowall]

For the second yes, why do you consider it potentially dangerous?

Two DSOs on a 2.5mm² cable?

Is there perhaps some linguistic pedanticism at work? ....

... The double socket in the kitchen is itself a spur. Should I remove this, is it potentially dangerous?

Riveralt may well haven taken your 'yes' to indicate that the kitchen socket was 'dangerous and therefore should be removed', whereas it's actually the dining room one (the spur from a spur which is the problem.

Kind Regards, John

Chicken or egg, me thinks.

 

[Shaneyboy]

Just to clarify, it is the dinning room DSO that I am considering removing, sorry for any confusion...

Kind Regards.

 

[JohnW2]

Just to clarify, it is the dinning room DSO that I am considering removing, sorry for any confusion...

Yes, as you will realise, that's what I assumed. Quite apart from anything else, removing the kitchen one but retaining the dining room one would be less than straightforward (although obviously not impossible).

Kind Regards, John

 

[Shaneyboy]

Luckily, the distance between the two is minimal so should be easy to just pull the cable out. Thanks for the interesting discussion, lots for me to try and understand.

Kind Regards.