No. of spurs v No. of ring skts.

[Duncan Bennett]

I am pricing to wire a kitchen and intend to feed it with one ring circuit.

The client is looking for 5 x twin skts. above worktop level, and as many as 6 x dedicated appliance sockets which he would like switched through a grid system above worktop level.

Chapter 7.2.2 (para 3) in the OSG states that " ... the number of non-fused spurs is not to exceed the total number of socket outlets and items of stationary equipment connected directly in the circuit."

I intended installing one - perhaps two - grids in the ring circuit, looping in and out of the supply side of 20amp switches (to maintain the ring) and then spurring off in 2.5mm to either an fcu or unswitched socket for connection to the appliance.

Am I able to do this, or should I install more sockets on the ring to make up the numbers - it does seem a bit odd to have to do that.

Any advice would be appreciated; I haven't used this system of labelled 20a grid switches before, normally I just include an fcu in the ring above the worktop and drop down to the connection unit/socket, but the customer is looking for a tidy job.

 

[topquark]

If you're feeding an unswitched socket can you not include a grid fuse?

 

[Inteificio]

I must admit I can't follow that description.

I intended installing one - perhaps two - grids in the ring circuit, looping in and out of the supply side of 20amp switches (to maintain the ring)

Also what is a FCU?

Probably really obvious, but not much sleep last night so brain is running tooo slow.

​

 

[tonycoysh]

Fuse every spur in the grid plate. Fuses are accessible and spurs are fused. You can get a fuse unit to fit the grid switch units. Then you have the option of having a connection plate below the worktop rather than a FCU or socket. I believe some manufacturers void the warranty if you cut the plug, but I know with my dishwasher I had to cut the plug to get it to fit under the worktop and use a connection plate instead.

I kind of think that the whole idea of a grid switch or FCU above the worktop is half pointless if you are going to then put a fuse behind the appliance anyway. If and when that fuse blows you still have to pull it all out to get at the fuse.

 

[topquark]

I must admit I can't follow that description.

I intended installing one - perhaps two - grids in the ring circuit, looping in and out of the supply side of 20amp switches (to maintain the ring)

Also what is a FCU?

Probably really obvious, but not much sleep last night so brain is running tooo slow.

​

Fused connection unit.

 

[Silly Sausage]

Chapter 7.2.2 (para 3) in the OSG states that " ... the number of non-fused spurs is not to exceed the total number of socket outlets and items of stationary equipment connected directly in the circuit."

That will be referring to spurs coming straight out of the back of sockets.

 

[Inteificio]

So is a FCU another name for a SFS or is there some difference?

 

[topquark]

Switched versus non-switched (both fused).

 

[Silly Sausage]

Carrying on from tonycash, run your socket ring where you want, then where you want to position your grid(s), loop the ring Lines & Neutrals through the double pole grid switches with grid fuses under each switch, then onto a connection plate/socket.

As for cutting plugs off, there are many members on here who are adamant that it does not void warranties. (I don't really know)

 

[Inteificio]

Some manufacturers will kick off about cut off plugs. You can normally argue the point that it is a competent person cutting the plug.
I cut off a plug on a failed PAT, sent it back for warranty and they kicked off.

Told them to get !"£$ed as a trained spark, they dropped complaint. I phrased it better than that to them ;-)

 

[Des 56]

I would say that if push came to shove and the question was decided in a court,the manufacturers would not have a leg to stand on and the judgement would be straightforward and against them
The problem being,who, or how many, would contest that manufacturers get out of responsibility excuse
Its far easier then,to avoid that issue by not cutting the plug off

Feeding outlets connected through a grid system on the ring is fine,there are those who say the 20 amp DP switches are not rated accordingly,but my own contention is that the "terminals" are rated accordingly

Though I am led to believe the manufacturers of the DP switches will not confirm they are suitable

 

[Duncan Bennett]

Thanks, all

But how does this work with the numbers I suggested? Each 20amp grid switch would then act as a radial spur from the ring, and 7.2.2 in the OSG says it can't exceed the number of sockets on the ring? I'd just like to see the confirmation in writing somewhere in BS 7671 before I price to insert a grid system.

 

[Engineer54]

You count each DP grid switch as equivalent to a socket outlet, so you haven't got more spurs than ring connections have you?? I'd hate to think of the amount of cables in the back boxes of these grid switches.... I bet it get's tight for space in there too!!

 

[Duncan Bennett]

... I'd hate to think of the amount of cables in the back boxes of these grid switches.... I bet it get's tight for space in there too!!

Well, I haven't actually tackled one myself, yet. But I can imagine it does get pretty tight :cry_smile:

 

[mickys86]

You count each DP grid switch as equivalent to a socket outlet, so you haven't got more spurs than ring connections have you?? I'd hate to think of the amount of cables in the back boxes of these grid switches.... I bet it get's tight for space in there too!!

They are very tight but the trick is to put a 47mm box in and set it back as far as possible