Why can't I do a spur off a spur?

[j b]

I'd like to run a radio off a spur taken from another spur in the kitchen. The appliance currently on the spur is an above hob extractor fan which has wiring that is nicely accessible as it is installed above the built in kitchen cupboards. The spur I would take off it would be about 1 metre long and be connected a radio.

I can see everywhere that you shouldn't take a spur from a spur but why not?

Taking a spur off the ring circuit in the kitchen is not easy because the wiring is buried under professionally laid tiles.

j b

 

[andy]

because ifs it unfused, you could draw too much current and melt the cable. if it was a fused spur, you can take as many sockets from that as you wish

also, 2.5mm² is rated 27A. the MCB will be 32A so the cable isnt protected againt overload, so there is a chance of fire.

 

[Big_Spark]

because ifs it unfused, you could draw too much current and melt the cable. if it was a fused spur, you can take as many sockets from that as you wish

also, 2.5mm² is rated 27A. the MCB will be 32A so the cable isnt protected againt overload, so there is a chance of fire.

Andy, couple of points...Firstly, it is an extract fan for a Hob..so the FCU will be a SWITCHED/FUSED Spur (Connection Unit), however, ideally, you should still not, fused or otherwise, spur from a spur.

Secondly, 2.5mm² is ONLY rated at 27A when clipped direct, if it passes through an insulating wall at any point on it's route, then it must be downrated to 18.5A maximum.

JB Have you determined if the FCU controlling your extract fan is 1: On it's own circuit or 2: Spurred off the ring Main or 3: Part of the ring main?

Also, when you say the cable is easily accessible above the unit, is this the feed from a lower level FCU that controls the Extractor?

 

[Lectrician]

Why not change the socket for the extractor to a double??

You could then simply plug your stereo in that is a metre away??





Or, get a dual accessory box, put a non switched FCU in the one side, and switched FCU in the other. 2.5mm supply into the unswitched one, link from the output of that to the switched FCU, with it's output for the hood. Then link from the INPUT terminals of this FCU to your new socket.

 

[j b]

Re: Big_Sparks question about the FCU....

The FCU for the hob extractor is spurred off the ring main. Its feed is taken off one of the double sockets in the kitchen. The extractor FCU is located on top of the kitchen units so the cable for it ( and the FCU itself ) is all easy to get at.


Re: Lectrician suggestion to change the socket for the hob extractor to a double socket.

The hob extractor is not on a socket it's on a FCU.


Re: Lectrician suggestion about using a dual accessory box, thanks for that I'll give it some thought to see if I can understand exactly what you are suggesting. I'm not a qualified electrician so I need to make sure I understand what you're suggesting and why it is a good solution before I go off and implement it.

 

[Softus]

Andy, couple of points...Firstly, it is an extract fan for a Hob..so the FCU will be a SWITCHED/FUSED Spur (Connection Unit)

Nobody said that an FCU was being used - that's your assumption.

however, ideally, you should still not, fused or otherwise, spur from a spur.

The original poster asked, effectively, why the thing that you say is "ideal" is, in fact, ideal.

JB Have you determined if the FCU controlling your extract fan is 1: On it's own circuit or 2: Spurred off the ring Main or 3: Part of the ring main?

He said it was spurred - do you have a reason for doubting it?

 

[Softus]

Re: Lectrician suggestion about using a dual accessory box, thanks for that I'll give it some thought to see if I can understand exactly what you are suggesting. I'm not a qualified electrician so I need to make sure I understand what you're suggesting and why it is a good solution before I go off and implement it.

j b, a dual accessory box is a variation on a standard double pattress - a standard double will accept oneplate, for example a double socket outlet. A dual box is designed to accept two single plates, because it is wider than a double and has four threaded holes.

If you use one of these, then the FCU will go on one single plate and the single (radio) socket could be on the second one. FYI, you can get a surface-mounted dual box that screws into a single sunken box and thereby converts it to a dual accessory outlet.

 

[Lectrician]

I was suggesting a dual for a SW fused spur for the hood, and an unswitched for the start of the fused spurs.



Your hood is currently fed via a fused spur, but you could simply put the hood's flex onto a plug top, and use a double socket - if the radio is not too far from the hood.

 

[Big_Spark]

Andy, couple of points...Firstly, it is an extract fan for a Hob..so the FCU will be a SWITCHED/FUSED Spur (Connection Unit)

Nobody said that an FCU was being used - that's your assumption.

Well unless it is a toptal lash up the extractopr should be controlled by a spur..as in a Switched Fused Connection Unit...commonly known by Sparks as a SPUR....

however, ideally, you should still not, fused or otherwise, spur from a spur.

The original poster asked, effectively, why the thing that you say is "ideal" is, in fact, ideal.

Although a bit alarmist in how he worded it, this point was clarified by Andu in his initial reply..no need to add to that information.

JB Have you determined if the FCU controlling your extract fan is 1: On it's own circuit or 2: Spurred off the ring Main or 3: Part of the ring main?

He said it was spurred - do you have a reason for doubting it?

He said it was a SPUR..now that could mean exactly what he later explains it to be, or it could be an assumption on his part as it is controlled via a SPUR..or FCU...

Now perhaps instead of simply coming here attempting to pick holes in others posts..you might like to add something constructive for JB..

 

[Big_Spark]

JB...

This is a dual accessory box fella..

And it can be found here

This is a Switched Spur..or FCU if you like..

Page for this is here

And this is a UNswitched Spur or FCU..

And the page is here

Hope this helps to clarify what Lectrician was explaining..

 

[j b]

Big Spark that last post was super for my level as it came with photo's and links. Excellent, thank you.

Many thanks also to Lectrician and Softus for their excellent suggestions and contributions.

Only Andy attempted to answer my original question about why you shouldn't use spurs from spurs which I now assume is down to overloading the spur by hanging too much stuff of it so thanks also to him!

regards

j b

 

[Softus]

...the extractopr should be controlled by a spur..as in a Switched Fused Connection Unit...commonly known by Sparks as a SPUR....

So, when a sentence contains the terms "spur" and "FCU", how does anyone know which is which? You way you imply that all electricians talk/write is ludicrous, especially on a forum where the words chosen are important. It's like someone saying when I say "road" I mean "traffic lights".

Although a bit alarmist in how he worded it, this point was clarified by Andu in his initial reply..no need to add to that information.

Agreed - since j b has thanked Andy for that.

He said it was a SPUR..now that could mean exactly what he later explains it to be, or it could be an assumption on his part as it is controlled via a SPUR..or FCU...

I guess that ambiguity is almost enough to qualify him as electrician then.

Now perhaps instead of simply coming here attempting to pick holes in others posts..you might like to add something constructive for JB..

Perhaps I would, but at present the removal of the confusion created by you is taking up all my time. Notwithstanding that, j b is happy that we've all contributed something.

 

[plugwash]

they are often reffered to as a fused spur but i can't say i've ever seen anyone reffer to one as just a spur.