Cable chased into wall- permitted zone?

[bureaucrazy]

According to BS7671, cables chased into a wall and plastered over must be within 6 inches of the ceiling or corners or running in line with an accessory either vertically or horizontally. Or they can be mounted on the surface of the wall. These rules are intended to prevent someone unwittingly drilling or nailing into a live cable that cannot be seen below the surface.

Is it permitted to have a cable partly chased into the wall and part surface mounted outside the 6inch zones and without being inline with a accessory? E.g. the cable is running vertically down the middle of the wall. 4 feet from the ceiling down is chased into the plaster but then it comes out and the rest of the run to the floor is surface mounted. Sight of the part that is surface mounted would imply that it may be unwise to drill or nail anywhere in line with it just as the sight of an accessory would. The part that is surface mounted is behind kitchen cupboards so is not unsightly. Does 7671 have anything to say about cables obscured by cupboards, etc?

If this is in breach of BS7671, then would installing an accessory in line with the cable make it compliant? What if the new accessory was behind the cupboard? Is there any other solution to get this to comply, (e.g. RCD) without having to get half the house demolished to install a new cable?

Thanks

 

[telectrix]

as i see it from your post, surface cabling is hidden. an accessory in line with the buried cable would have to be visible. e.g. above the cupboard. you don't say what the cable feeds. if it is a single accessory, why not fit a FCU high level, where it can be seen. RCD is not a get out for wrongly routed cable.

 

[jase]

tricky one really, i mean even in a living room, if you stuck a sideboard in front of a socket at 450mm above the floor, then someone decides to hang a picture above the sideboard, they might not realise that the socket is there even though the cables are in the prescribed zone still dont mean it is safe from being penetrated by a nail, i guess this is why any cable buried less than 50mm below the surface must be either protected by an earthed metallic sheath, or RCD protected. Whenever i am doing kitchens i wonder wether all that safe zone stuff actually matters anyway, how many kitchen fitters actually know or care about safe zones so could potentialy screw through a cable anyway? which is why i like to have a kitchen layout so i can put sockets and stuff in the middle of wall mounted cabinets!!
I think if the circuit is RCD protected you should be ok

 

[SPARTYKUS]

Conduit not sheath. Nail will go straight through sheathing. The earthing of it is not the only point, its the mechanical strength of steel conduit thats relevant.

I disagree I do not think its ok! Do it right .... Or its a bodge.

Is there a more circuitous route? Tell us more.


s a recent study i read of RCDs found out of their sample that 3% (i think!) were faulty. RCDs fail. Steel
pipe doesnt.

 

[jase]

the point about earthed sheath is that it is earthed, not wether it can prevent penetration, sheath is the wrong word, in the regs its says earthed metallic covering, it also says as long as it is within the zones (reg 522.6.101 (v) it shall be be provided with additional protection by means of an RCD.

so in short, out of zone a definate no no, within the zones at the very least should have an rcd, so stick a socket on the wall where the cable is surface, and bung the circuit on an RCD and job done

 

[Deleted member 26818]

A cable concealled in a wall must be protected by one or more of these methods:
1) Buried at a depth greater than 50mm.
2) Have an earthed sheath.
3) Be contained in earthed conduit or trunking.
4) Be mechanically protected (no requirement for earthing) sufficient to prevent penetration by a screw or nail.
5) Run in a prescribed zone and protected by use of a 30mA RCD.
Use of a 30mA RCD on cables not in a prescribed zone would be a departure from the requirements of the Regulations.

 

[Silly Sausage]

a recent study i read of RCDs found out of their sample that 3% (i think!) were faulty. RCDs fail.
pipe doesnt.

Mr E54 will like that!

 

[Richard Burns]

One thought is if there is a cable running down then to what is it attached surely the cable is not pointless if you can run the cable in line with the item to which it is attached then there is no problem.

If not one or two ways I can think of managing this.

Where the cable is chased in to the wall put it it metal conduit connected to an earth cable and on the surface run also run an earth cable to the accessories earth connection.

Run the chased cable through an empty back box with a blank plate, possibly may be an accessory and avoids any odd connections.

 

[jase]

but if that back box with blankk plate is behind kitchen units then there is still a buried cable above worktop level that on sight no-one knows about, hence even if cables are in permitted zones they still need RCD protection if buried less that 50mm deep unless cover with an earthed metallic covering or run such a way as to prevent penetration

 

[Silly Sausage]

but if that back box with blankk plate is behind kitchen units then there is still a buried cable above worktop level that on sight no-one knows about, hence even if cables are in permitted zones they still need RCD protection if buried less that 50mm deep unless cover with an earthed metallic covering or run such a way as to prevent penetration

These zones are, essentially, verging on pointlessness! The general public have no idea about them and will happily drill anywhere well beyond 50mm, I've done it myself on my own wiring once fitting a kitchen cupboard.

 

[bureaucrazy]

Thank you all for your contributions. Some of you have asked for more detail so I should explain why moving the cable is problematic:

The wall in question is in the kitchen on the ground floor. The bathroom is on the floor above and the cable is a 10mm 2+E for the shower. The kitchen walls only have a 2mm layer of skim plaster straight onto the bricks. When the kitchen layout was designed, the builders put all the cables in zones that would be permitted according to the kitchen layout and accessory positions. Rather than put an inch thick layer of plaster on the walls and chase the cables and sockets into that, the builders chased the cables and sockets into the bricks themselves to avoid plastering (this was far more work than plastering would have been). The shower cable runs down the wall directly in line with and behind the cooker point and comes to surface below the worktop level. Unfortuately the original kitchen design was a poorly designed layout and now it would be better to move the cooker 2 feet to the left. If the cooker point is moved, it won't be in line with the shower cable anymore and the shower cable will need moving to be in line with the new cooker point or other accessory. I am worried that chasing a cable upto 20mm deep into a single brick thickness party wall may weaken the wall. This has already been done once and chasing another channel 18 inches to the right could weaken the wall further. Also, it as an awkward and dusty/messy job with angle grinder and chisel.

I will be totally aware of the location of the cable so there is no chance of drilling into it by mistake. Furthermore, once the tiles and kitchen cupboards, etc are installed, no one is likely to hang a picture there. In fact the shower cable will be behind the cooker splash back and cooker hood. I was going to put the cooker termination point in line with the shower cable below worktop level, but as one of you suggested I may look at positioning the fused spur for the extractor hood in line with the cable is possible.

All this wiring was done a few years back before the part P thing came in. I do care about the safety and compliance of the installation which is why I am posting on this forum for a solution. It doesn't make sense to me to risk weakening the structure of the wall when in practice, there is no risk of someone drilling into the cable by mistake given it's location behind the cooker. I am more worried that one day in the future, some official inspector will come along and complain that it is non compliant and make me rip out the kitchen to change it. If for practical reasons, I leave the cable where it is and move the cooker point, what kind of trouble could I get into? Would the property fail a PIR?

 

[telectrix]

from what you have just posted, i would be inclined to leave the cable as is. even though it's a domestic installation, it is under the control of a "skilled person" (you). assuch, there is only a remote chance of the cable being damaged.

TIN HAT READY.

 

[Guitarist]

I take it you are definitely chasing a new route for the cooker switch anyway, but simply don't want to go as deep as it was before? Maybe running another shallow chase next to your new cooker point would be acceptable if you were to go through a backbox and use a blanking plate. Although you would have 2 shallow(er) chases, at least the blanking plate would give away the fact that cable is being run vertically or horizontally.
Please tell me if you think I am talking rubbish here

 

[bureaucrazy]

I think the blanking plate idea would be acceptable as far as the zones are concerned. The question is whether it is still ok if the banking plate/accessory is below the worktop level where it is not seen as readily. Do the regulations say that you cannot put fitted cupboards or any fixed structure that conceals the accessory from ordinary view? If there is a working socket that is in use, even if it is concealed behind a cupboard, the occupier would be aware of it's location and therefore aware that there is potentially a cable in line with it. If it is a blanking plate and not in use, then they are less likely to be aware. I can put the plug socket to power the washing machine below the worktop but inline with the shower cable. I think this is the answer?

Given that the cable will be behind a tiled splashback, the only situation I can think of where the cable could get drilled is if say the cooker hood needed replacing and a new owner of the house drilled into the cable by mistake doing that, but I can leave a bit of the shower cable visible (not plastered over) behind the cooker hood to make it obvious where it is to prevent that.

Q1: Do the regulations permit a cable to be run chased beneath plaster where part of the run is on the surface? Surely that is as good an indicator not to drill as being in line with an accessory would be?

Q2: If I leave the shower cable where it is and remove the accessory (cooker point), but part of the cable (behind the cooker hood and worktop) is not buried in plaster, so you can see where it is (with a little investigation) am I violating BS7671?

Q3: If I am violating BS7671, how serious would it be in terms of an electrical condition report? (PIR or EICR) What code e.g. C1 or C2 or C3? What about putting the washing machine socket in line but below the worktop?

 

[Guitarist]

I was thinking more of putting the blanking plate next to the cooker point above the worksurface (away from the cooker) just to indicate that there is a cable somewhere on that vertical or horizontal plane.
I think it has to be obvious where cables may be run, rather than "with a little investigation", but I may be wrong. I know that there will always be occasions when furniture etc might obscure a switch or socket, but I'm sure most (sensible) people would look behind furniture before drilling.
Regarding q3... Not sure if your washing machine socket is part of the ring or a spur, but for arguments sake, if you installed a fused spur above the worktop feeding the washing machine socket then the cable run would be obvious.

 

[Dan]

Just bumping some threads in the Electrical Wiring Theories and Regulations forum category here on our Electricians Forums. If this specific topic isn't current, just ignore it, it'll drop off the list in no time. However, if it's something you'd like to contribute to, feel free to reply and bring it back into current discussion.