Prescribed Cable Zones: What You Need to Know
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- Опубликовано: 31 май 2024
- BS7671UK wiring regulations define prescribed zones (cable zones) to run cables within walls to avoid this situation. Installing cables in these locations reduces the risk that someone will drill through or hammer a nail into a hidden cable.
Even if you aren't an electrician understanding the prescribed areas in which cables could be located will reduce the chances of damaging a hidden cable.
In this video, we explore why prescribed zones aren't "safe" zones, the requirements for RCD protection and other options to protect cables buried within walls.
More electricians Q&A here - • ELECTRICIANS' TECHNICA...
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00:00 Prescribed cable zones
00:40 Options to run cables in walls
01:40 BS7671 - 522.6.602 Cable zones
03:00 Vertical and horizontal cable runs
03:40 Changes of direction to wiring accessories
05:00 Share this information with non-electricians
05:20 Prescribed zone not a safe zone
05:40 Additional protection by RCD
06:40 Other options 522.6.204
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Check out the Evolve range of switches and sockets 👉ruclips.net/video/RDOriUvWYQo/видео.html
I'm from America but I enjoy learning about all the differences across the pond.
As a security system engineer with 4 years experience I'm watching after going through a cable for the first time today. Handy to learn
To your point on cooker switches. If you were to run the feed back up to the ceiling and down vertically to the lower outlet this would be a concern to me as the lower accessory will be completely hidden by a kitchen unit or installed appliance. The user can't readily see the outlet so would not be aware of position the zone even if they were aware of the regulations. This would apply to any outlet installed behind/below kitchen units or any other 'fitted' units.
Plumber watching to remind myself where/where not to drill. Thanks.
Wow, we're truly multi-cultural now!
I only run cables vertical from an accessory . Never horizontal unless 2 accessories are very close together or a cooker outlet . The few DIYers that have a bit of knowledge and even other trades to some extent only consider cables to run vertical.. That’s the way we was always taught to do it.
Several times I have been called out to damaged cables and the DIYer or carpenter has said that cable shouldn’t be there . When I point out it’s in a safe zone and complies with regs they can’t believe it and say that’s crazy.
As my boss used to say the regulations are the minimum standard we have to comply with .
Fair points here, hopefully more content like this will help educate other trades as well. 👍
Ran a cable here horizontally in a stud wall to give a socket on the other side of a bed but was never happy with it for exactly the reasons stated above - it was permitted but would anyone following me think to check. Took it out and ran it under the floor when I had the floor up to re-run CH pipes.
Went to look at a neighbour's new kitchen not long after the death of MP Jenny Tonge's daughter in 2004 through electrocution due to a screw penetrating a cable outside a prescribed zone. It was clear that a cable must have been run diagonally between two fittings so I pointed out that this was very wrong and why, and suggested they contacted the company that supplied and fitted it all.
They came back saying it was fine because the cable 'went down the cavity'. But it was a solid party wall, no cavity, so were they calling the gap between plasterboard and blockwork the 'cavity'? There was no RCD protection on the property at the time and I never did find out if the problem was dealt with - I suspect not.
Nicely put and very consistent Joe. Thanks for sharing.😀
Grid switches look lovely but when it comes to 2nd fix they can be so tight for space. Id recommended using 2.5 flex with ferrules to give you that extra play in the back box.
Genuinely, what on earth is the argument AGAINST the cooker example where the cable changed direction but is still within the zones of the two accessories ?
A suggestion that the regulation quoted means the cable can run vertically or horizontally, not both.
@@efixx blimey - that’s some linguistic gymnastics going on there 😬
Thanks
One direction was formed by the switch and another direction was formed by the outlet so technically it's not both as the direction is one chosen per one formed, so a silly debate IMHO
Yur, not having a pop at anyone's opinion but felt we wanted to clarify it. 👍
I can't see anything that would raise any question
Thank you very helpful indeed!
I discovered that one of my double sockets in the kitchen was a spur feeding another double socket on the same wall some way away at a lower level. The circuit from which these are fed is a RFC. The cable was running diagonally!
There is no FCU prior.
I am not an electrician but I do know that for starters there should only be one 'accessory' (single or double socket) on a spur, and as for the cable running diagonally... I know a long time ago the regulations allowed two single sockets on a spur, I guess someone decided to upgrade "them" to doubles at some point.
Even then I think the prescribed zones were vertical only.
I only discovered this before doing some DIY work with some cupboards! I'm going to get an electrician in to check out my installation overall and in the mean time I'm going to blank off the first 'spur'. I believe you can get blanking plates that fit over a socket, so you don't have to touch the electrics.
After recent fresh discussion on twitter I found myself watching this lol. Good to see you guys setting it out and it even clearly states Efixx on the video, T shirts and logo. No Niceic in sight! Top job.
Bit of a weird one that eh? 🤷
@eFIXX very clearly an attempt (poor one) at self promotion at the expense of any and all others. Blinkered selfish and destructive behaviour.
Question how we all see regs differently of course. But question business ownership, structure and integrity based on a colour? Embarrassing behaviour.
I have never been comfortable with the 150mm from the corner of the room as this is where chippy nails skirting. I would be interested how in domestic how outside lights are wired where there is not a lightswitch on the inside?
Not your issue if another trade decides to invade the prescribed safe zones
It is if you have keep going back to repair it, who wants to do that even if getting paid.
Good question, watch out for a video in the future!
Nice to know..for pictures and things
Just love it when cables are hidden behind arcitrave around doors and windows.
I come across a lot of 1950/1960 properties where I find cables behind skirting boards. Was this previously an acceptable cable zone?
I have a house built in 1999. During wallpaper removal and decorating we found a 2.5mm twin and earth buried just under the plaster covered in black/yellow Hazard tape. I take it May derailing the house builders were exempt from any electrical installation standards. Neighbours found similar in kitchen replacement project recently as well. How should the cable I found have been installed?
I do feel slightly for the kitchen fitters as if all appliances are brought to the same point in the units then the cables can begin spread quite wide unless chase depth can be deep enough to bunch together (whilst compliance is met). Times like this require for spot on kitchen drawings & electricians allowing for how much walls are being brought out and checking regularly that client is sure the spurs are going in said position.
Some good points here. 👍
We had an issue once where our nextdoor neighbor drilled through a lighting cable on our side of the wall. Our cable was installed about 10mm deep in 100mm brick, behind plaster, and the neighbor drilled much too deep, through crumbling brick. (Nearly came through to our side)
This was caused by the fact this is the party wall between our two properties, which is only 100mm brick. And the neighbor didn't know we had installed a cable in the wall in this location.
Question. In a previous house, the cables to the light switches were ran vertically, so no cable protection needed (apart from a RCD). However, the cables were originally rubber and had a metal U shaped cover. As the house was built before lighting circuits had to have an earth conductor, none of these metal covers are earthed. If new PVC modern cables were threaded through these existing cable runs under the existing metal covers, would they need to be bonded to earth?
It's very unlikely as the capping (the metal us shaped cover) is neither an extraneous nor an exposed conductive part. 👍
If those cables run in the protected zone, and are not positioned outside of the width of the switch, then I agree with the response provided by eFixx.
If those cables fall outside of the protected zone, then it can be argued that the metal covers are forming a protective metal shield to the cables, and then that metal cover needs to be earthed.
@@deang5622 - all were within the width of the switch plate. Thanks all for the answers 👍
What's the view on "borrowed" proscribed zones? When I did my house (I am in Scotland so I am allowed to) in the end I ran the cable for the smoke detectors up the wall and through a light switch to get into loft. I decided that was better (and less work) than channelling through the breeze block (made from real genuine breeze it makes an awful mess) on the other side of the door in the corner of the room. That would be a proscribed zone but nobody would have clue anything was there.
Was the smoke alarm on the same circuit as the lights ?? If not you couldn't safely isolate to work on the switch .
One could use flexishield which has an earthed metallic sheath, and has protection for up to a B curve, 40 Amp MCB.
Here's a question. I have built internal stud walls (timber, 3 and 4 inch thickness) and run various cables such as data, KNX, down to light switches. Our sparky has come along and added twin and earth down to 13A sockets below, and in some cases he has clipped the whole lot including the data I have run, to the nearby vertical stud. So now the wires are not running *exactly* vertically in line with the centre of the backboxes (or rather within the imaginary vertical lines created by the width of the backbox). I can think of one case where the cables are perhaps 1 or 2 inches left or right from the *edge* of the backboxes (clipped up on side of stud). It doesn't bother me as I'm ply-backing most of our walls, and I will know to use 30mm screws if ever I screw into a wall. Also I'm photographing literally every wall from every angle before they are covered up. Also I'll let nobody touch my walls whilst I'm alive :) But I guess the point is that it still needs to be compliant for when I'm dead and gone. So - is this okay, even if the cables are technically not within the exact vertical lines created by the socket width? If the answer is "technically no", then can you add "but it is not too terrible"? Or do I need to address this?
They are outside the zones so no.
More than 50mm with RCD is okay
Did you say he ran band I and band II cables close together? Segregation?
Technically not permitted unless you undertake one of the following: The cable must be over 50mm below the surface. If the wall is made from metal then it will need RCD protection, or
The cable should be armoured with an earthed armour or metal sheath, or
The cable should be in metal trunking or conduit which is earthed or,
It should have protection from at least 3mm steel.
I will caveat this, because I don't know if this is 18th Edition and I can't bothered at this time in the evening to check.
To my mind an RCD in the consumer unit should provide sufficient protection but I don't want to state that as the definitive approach to dealing with the issue.
Not ok as not in zones, should of installed noggins to clip the cables and keep them in zone, there is always the proper way to do things.
Why are apprentices of other trades not being taught about the prescribed zones?
I must admit the one in the corner is suspect, where will a plumber install heating pipes or alarm installers fit pir detectors.
And the skirting gets fixed at the ends
@@supersparks9466 that's true, but most wood butchers are using pins and either foam or no nails, so they could be safe from them😀
These details are not covered in the building regs, they are in BS7671, and other trades don't cover that.
It really needs a government level initiative to tell the industries to start working together.
Apparently not enough!
When you change a old fuse board with new one what do you recommend
RCBO or double RCD
Kind regards
Peter
See this video for our take on this.
ruclips.net/video/ikwHKpM8RjU/видео.html
Not just SWA, the likes of Ali-Guard can also be used, as it has a metallic covering that can be earthed, so can be used to run diagonally from the cooker switch to the outlet plate, for example, at less than 50mm deep - only problem is it's tough to work with if it needs bending.
Ali-guard sounds interesting do you have any product links. 👍
Hi lads, is there something at your end that's deleting my replies - I've tried replying twice, with my replies showing up as expected but within a few minutes they're gone?
@@johnhoward2104 If your reply contains a weblink it maybe youtube purging it automagically. If so you might have to type dot or change to an _ or similar
50mm depth ...can u get it that depth...
or can u install cable in a protective conduit 18th edition.
yep, steel conduit is acceptable
A quick check reveals the following alternatives must be used if cables cannot be run in the cable zones:
The cable must be over 50mm below the surface. If the wall is made from metal then it will need RCD protection, or
The cable should be armoured with an earthed armour or metal sheath, or
The cable should be in metal trunking or conduit which is earthed or,
It should have protection from at least 3mm steel
If it at 50mm will an electrical cable detector still work?
Good question, depends on the tester and what's between the cables and the surface. 😬
Had a Sky satellite installer hammer the cable clips for the co-ax cable through surface plastic trunking that carried a 2.5mm 20A radial to a garage once. One clip went straight through the middle of the cable. Just as well it had a RCD…
No zone in the world safe enough to protect against stupidity! 😂
Well known that cable TV and broadband cable companies don't employ skilled electrical people for doing installation work, they employ brickies.
Not a sparky so this is news to me (commercial security). We're generally not drilling into solid wall and if we are we're looking for hazards first.
Did have diagonal mains cables in our flat, only found after stripping the wall paper!! 😵💫😖
Nightmare!
I found the diagonal cable in my house in the traditional way. When putting up shelving with a corded drill. The resulting surface junction box stayed for about twenty years until a full re-wire.
Can understand why horizontal can now be used....etc etc. but still..an accessory...cables either up or down....
So I was putting curtain rail up by a window (DIYing it ofc) and went through a cable. Cable was sparking and had to call an electrician in to sort it out. If only I knew about this then as I didn't think about horizontal wire placements along the top of the wall. No RCD or anything as we still have one of those old boards with physical fuse wire.
Interesting, was it within 150mm of the ceiling?
@@efixx Honestly, not sure. I was just putting a hole in the wall for the plug and screw and saw some sparks. Stopped immediately and the cable kept sparking periodically.
Turned the electric off and called an electrician in to terminate the cable safely.
Best thing to do. 👍👍👍
@@efixx to this day, the curtains were never put up and we still have an old fuse board with actual fuse wire. Our lighting circuits have no ground either so only class 2 light fixtures for us. A rewire has always been out of budget.
Prefer the term prescribed Zone rather than safe zone which is a bit miss-leading for non sparkies. Should be called the bang ouch f&2;£k zones.
Keep an eye out to see if this terminology makes it into the 19th edition! 😂
The best we've had was a kitchen fitter drilling through ALL the circuits coming out of the CU (which he'd installed a b*oody kitchen cabinet round so he knew the cables were likely to be there). Cost him quite a bit
🤦♂️ Just drill it and hope for the best...
Best I saw was our basement company who gutted the internals of two floors of our 5 storey house, and literally went at the load bearing walls with big breakers. Straight through metal capping. Sparks flying, zero craps given - just carried on. I had to then go and strip all the electrics out myself after taking the consumer unit out! The mess of mangled capping and wire that had been left live after they finished… both hilarious and horrendous at the same time. (They did the same with sewage, leaving me with *other* types of mess to sort out as well. Oh and these guys saw radiators, and just cut the pipes, water pissing everywhere, then sent a junior out to local shop to buy a push fit stop end. Seriously.)
@@MatSmithLondon good gawd. Hope they didn't get paid
@@TheChipmunk2008 well yes they did get paid because they spent 2 years onsite with about 6 blokes.
@@MatSmithLondon OOF, i'd have had them off site when i saw that
It's frustrating that electricians read this and think they can use the 150mm in the corner of the kitchen. This is not a licence to put cables in places where they shouldn't go and cables should never go in the corner of a kitchen because that is where cabinet brackets go.
interesting to see the UK perspective. in the US, there is no such thing as a "prescribed zone" to have cabling within a nail's depth of the surface. anything within an inch and a half of the unfinished wall structure SHALL be protected by 16 gauge steel plates or the equivalent.
Sounds like a sensible option - what is a nail depth defined as?
@@efixx on a framed wall, it is an inch and a half from the face of the stud (38.1mm)
we also don't allow nonmetallic cable to be embedded in masonry at all. I believe it can be threaded inside hollow blocks, but I couldn't chase cables in the plaster the way it is done in the UK.
Interesting thanks 🙏
I don't like running cables horizontal let alone diagonal.
Horizontal is permitted within the regs and people will quite legally do it. So there is nothing wrong in it.
@@deang5622 Indeed, there seems to be a hatred for it though.... not sure why
@@TheChipmunk2008 People might have a personal preference for which way they want to run a cable, and there is nothing wrong in that, just so long as they stick to the rules, but they can't criticise others for doing something different when the rules are being followed.
Nothing wrong with horizontal especially for worktop sockets, less chance of that pesky kitchen fitter drilling them.
@@supersparks9466 A few years back I had a run in with the nicec inspector ,he didn't like the way I had run a cable to a cooker fan unit , my boss said don't argue move it .Mr kitchen fitter drilled a neat hole in it !
My question would be how visible an accessory has to be on the wall in order to define a prescribed zone. For example I've seen a well-regards RUclips spark describing how an accessory (fcu) at the back of a kitchen cupboard defines a horizontal zone across its whole wall - which I consider somewhat optimistic, shall we say. Clearly an electrician can't be blamed if a homeowner puts a big bookcase in front of an appliance that defines a zone but surely if fixed furniture prevents the location of an accessory (kitchen cabinet, pan drawers, maybe even a kitchen shelf) from being easily identified then that accessory's ability to define a zone is impaired.
Great question. I'm first fixing a kitchen at the moment and wondered the same. In the end I put a double socket beyond the base units so there could be no doubt of the existence of a horizontal zone.
The zone is not defined by articles placed in front of the wall.
The question is whether you are able to contain a cable within the zone because of obstructions in front of the wall, and to what lengths should you go to to comply with the zoning requirement.
Good question, I'd ask if the accessory at the back of a kitchen cupboard complies with 132.12 for accessibility... 😬
I think I know whom you are referring to. I think he would benefit from watching this video. from memory the accessory was at worktop level, cable route went up turned 90 traveled along straight into the extractor. In my view the route should have been straight up from accessory into the 150mm from ceiling and dropped into the extractor fan. I was pretty unimpressed for his lack of ownership of a bad installation. Will be heading back to this vid to check my facts cause what Do I know I’m just a chippy who tries to keep a finger on the pulse of what is responsible as per regs!
it is only electricians that keep to any sort of zone, i have hit pipes a few times in random places, once going horizontal 75cm across a wall found and ruptured a gas pipe when chasing up for a socket
Good question - let’s see if any plumbers chip in
Yeh, and what about data wiring? (Is data wiring covered in the regs? I presume not, because I don't need a certification to run data...)
@@MatSmithLondon guidance for various industries (data, security, etc) only says not to run alongside mains cables, not actually where is good... 🤷
@@MatSmithLondon Some low voltage comms is covered by the regs i believe (specifically the bit about premature collapse)
@@MatSmithLondon Data wiring is typically very low voltage (SELV) and doesn't present any electrocution risk.
Generally it is not a good idea to run data cables along side power cables because you can get inductive pick up in the data cables. Having said that, cables such as ethernet used balanced transmission and the 50Hz mains hum is induced in both positive and negative going signals in the balanced pair, and this then is common mode noise. The differential input receiving amplifier on the end of the balanced signal lines will remove that common mode noise. So it perhaps is not the problem it might initially seem to be.
I've once had to use swa in a bungalow to feed power to 2x external wall lights which they decided on after having the wall rendered.
You can chase down the inside , fit a box , go through the back and fit a blank plate . The blank plate would indicate something was buried in the wall .
@@dennisphoenix1 you could just looks really naff
@@MT_T991 maybe it would. But its compliant 😉
@@dennisphoenix1 oh for sure, but Essex big house folk are fussier than most 🤣
What about mcb
How about a plan included from your sparky exactly where the cable runs. Is that not easy?
Makes you wonder why all cables buried in plaster aren't just protected by flat metal capping, as a matter of course.
Even with your vast acquired knowledge of 25 year's! and I fully accept that modern standards are much safer, you can bet your life there are still historical domestic installations out there where cables will be run all over the show!
It's still hazardous, rather install a conduits use single core wires. The bear cables, is not proper cable management
ah yes, a question i was going to ask has been answered
we've got a plug in the wall in one room that is supplied from the other room on the other side of the wall, but the wall is one brick thick with potentially 10mm of plaster either side but it also sits within the zone between two plugs
plus i know it's there and we've had the walls freshly plastered so no one is going to be drilling holes in there any time in the next 100 years 🤣
Or MICC!
Yup! 😃
As usual you haven't answered the most pressing question you teased and clickbitten in the video icon - having all the help from your advisors - do you know if that shabby piece of metal from Wickes comply with subpoint iv) of 522.6.204 or are leaving interpretation to each of us individually for as long as this half hearted, vague regulation remains in the sparky's bible?
It definitely doesn't comply with indent iv) it's only there to protect against the plasterers trowel. I don't think we teased anything about capping in the thumbnail. 🤷
All these regulations can be replaced with a simple, 'all cables need to be protected with a metal cover'.
A challenge in a stud partition wall.
What a waste of money. And if you think I can't drive a nail through a "top-hat" type of metal cover with one blow; then you are living in a very delicate world.
in the US, we have that regulation. and yes, Jim, you CAN turn a nailgun up high enough to punch through a nailplate, but at that point, it becomes your problem if you do it.
Interesting overview, my only addition is to never use the term ‘common sense’ to any training video. It does not exist, only what you have been taught and learned.
You can’t say intrinsically safe! You’re ruining compex lingo there 😂
Gave the closed captions something to think about... 😂