hidden cable depth clarification

[oxfordjoe]

Hi
1) I have an unspurred single socket on a ring main

It is on a plasterboard/partition wall

I want to spur directly horizontally or vertically to a new socket or FCU

I think that my new cable will thus be in safe zone and I WONT have to bury the cable more than 50mm? Is this true? i.e. I can chase cable close to the surface?

2) p.s. a related spurring question , "if original unspurred socket was a double socket, could I spur off it"

 

[electronicsuk]

I think that my new cable will thus be in safe zone and I WONT have to bury the cable more than 50mm? Is this true? i.e. I can chase cable close to the surface?

I think you may have misunderstood the regs. Burial >50mm deep is one method of negating the requirement for RCD protection of the wiring. If the circuit is RCD protected, which it will have to be as it's supplying <20A socket outlets for general use, then you can run standard T+E cable at whatever depth you like, as long as it's within the safe zones.

2) p.s. a related spurring question , "if original unspurred socket was a double socket, could I spur off it"

Yes, it makes no difference if the originating socket or the spurred socket itself are single or double. As long as you ensure that where you're taking the spur from is definitely part of the ring final and you don't take more than one spur from any given point on the ring, there's no problem.

 

[rebuke]

1) Horizontally or vertically from an accessory is in a safe zone, so there is no requirement from that point of view to bury it >50mm.

However, the other requirements apply, such that if it is just T&E or similar, you need to ensure it is protected by an RCD, so if there is no RCD on the circuit, you will either need to add one, or replace the existing socket with an RCD spur unit, and come off that.

If you're spurring to a new socket, then the new socket will need RCD protection anyway.

2) Yes, as long as it is actually on the ring (and not a spur that has been spurred from itself), you can take a single unfused spur off it regardless of if it's a single socket, double socket, FCU or whatever.

 

[SparkyNinja]

I want to spur directly horizontally or vertically to a new socket or FCU

Spur from the existing spur? Or spur from the ring?

I think that my new cable will thus be in safe zone and I WONT have to bury the cable more than 50mm? Is this true? i.e. I can chase cable close to the surface?

The cable will have to be >50mm in the wall unless the circuit is protected by an RCD, or if you were to use a cable with an earthed sheathing of some kind.

2) p.s. a related spurring question , "if original unspurred socket was a double socket, could I spur off it"

The fact that the socket is twin or single is irrelevant

 

[SparkyNinja]

Is an RCD present?

What is the use of this spur intended for?

 

[ericmark]

1) Horizontally or vertically from an accessory is in a safe zone, so there is no requirement from that point of view to bury it >50mm.

(v) be installed in a zone within 150 mm from the top of the wall or partition or within 150 mm of an angle formed by two adjoining walls or partitions. Where the cable is connected to a point, accessory or switchgear on any surface of the wall or partition, the cable may be installed in a zone either horizontally or vertically, to the point, accessory or switchgear. Where the location of the accessory, point or switchgear can be determined from the reverse side, a zone formed on one side of a wall of 100 mm thickness or less or partition of 100 mm thickness or less extends to the reverse side.

Is referred to in next regulation.

522.6.7 Where Regulation 522.6.6 applies and the installation is not intended to be under the supervision of a skilled or instructed person, a cable installed in accordance with Regulation 522.6.6 (v). and not complying with Regulation 522.6.6 (i), (ii), (iii) or (iv), shall be provided with additional protection by means of an RCD having the characteristics specified in Regulation 415.1.1.

In other words "Safe Zones" only apply when you have an electrician on site with respect to RCD protection. So where adding a socket where the ring main is not already protected if you want to use a RCD socket you need to supply it with one of the following cables.

BS 5467, BS 6346. BS 6724, BS 7846, BS EN 60702-1 or BS 8436

The last is Ali-tube which seems great until you try an buy some. A whole role is a bit much to wire one socket.

So either fit RCD in board or fit RCD FCU seems nothing is easy any more.

 

[oxfordjoe]

Thanks for your excellent and very quick replies.

1) The current sockets ring is on the RCD protected side of the consumer unit. I do not remember the rating of RCD though and wont see it till the weekend

2) The new sockets would be for repositioning the TV in the living room and separately adding sockets in bedrooms.

3) I am spurring off a socket on the ring main, not spurring off a spur. Checked by the numbers of wires and a continuity test.

4) In the living room I would like to keep the original single socket in place and spur off it to a 13A switched FCU before the sockets to the TV etc so I can switch TV etc off all at once without fiddling behind them. If TV is wall mounted at any point i would use a 3A FCU flex outlet if no space for plug. I saw this on another post here. Anything crazy or illegal there?

So, Single socket on ring, spurs to 13A switched FCU which leads to sockets for TV etc.

5) New sockets in bedroom would be straight forward single or doubles

6) Worth asking the question here that if I had had to use 13A RCD FCU would this replace the original socket on the ring and then feed the new sockets OR would/could it be on a spur off the original socket and then feed the new sockets.

They must sell a lot of 13A RCD FCUs these days

 

[martinxxxxxx]

They must sell a lot of 13A RCD FCUs these days

I devote 50% of my van space to them

 

[electronicsuk]

4) In the living room I would like to keep the original single socket in place and spur off it to a 13A switched FCU before the sockets to the TV etc so I can switch TV etc off all at once without fiddling behind them. If TV is wall mounted at any point i would use a 3A FCU flex outlet if no space for plug. I saw this on another post here. Anything crazy or illegal there?

Nope, nothing crazy or illegal to be seen there. Plus, you can have as many sockets on the load side of the FCU, as the entire spur is limited to a maximum of 13A by the fuse in the FCU.

6) Worth asking the question here that if I had had to use 13A RCD FCU would this replace the original socket on the ring and then feed the new sockets OR would/could it be on a spur off the original socket and then feed the new sockets.

It would be fine to run it as a spur off the original socket, assuming it, hypothetically, is part of the ring final.