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Topic Title: Escape route wiring
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Created On: 12 May 2018 02:15 PM
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 12 May 2018 02:15 PM
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ben22

Posts: 11
Joined: 26 March 2013

Can any one explain how this applies to a domestic rewire situation and typical approaches used.

Domestic isn't my normal area of work, I'm more commercial/industrial maintenance
 12 May 2018 03:57 PM
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AJJewsbury

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Joined: 13 August 2003

I presume you're thinking about the requirements of regulation 521.11.201.

Basically you need to ensure that cables can't fall into the way of anyone attempting to escape from a fire (or rescue personnel gone into make sure that no-one's left inside) - so you can't rely on the likes of plastic clips or PVC trunking to hold cables up as they'll melt in a fire.

BS 7671's definition of an escape route is 'path to follow for access to a safe area in the event of an emergency' - so is usually taken to mean everywhere between anywhere someone might be when a fire breaks out and the outside - so basically all habitable areas (not just designated emergency exit doors and corridors).

In domestic settings, most cables are concealed either above/behind plasterboard or chased into walls and plastered over - and as plasterboard etc is reasonably fireproof that's usually adequate to restrain cables during a fire.

Surface mounted cables might need a bit more thought - if say vertically between a floor and plasterboard ceiling and fixed above that so it's not likely to move significantly even if the clips or trunking on the wall give way there's probably not much of a problem. Horizontal runs probably need some 'fire proof' support though. For T&E in trunking you can get metal fire clips - e.g. http://www.tlc-direct.co.uk/Products/DLSD30.html - and for round cables metal P clips (e.g http://www.tlc-direct.co.uk/Products/FTWP32.html or http://uk.rs-online.com/web/p/p-clips/2988104/ ) instead of traditional plastic cleats or clips.

There's still some debate about the best way to attach fireproof fixings to the structure - some have suggested that ordinary plastic rawl plugs are fine for horizontal fixing into masonry walls etc - although others have shown that they can fail during a fire when used to support vertically from a ceiling. Various masonry screws that don't need a plug are an option anyway. An ordinary screw through plasterboard into structural timber seems to be fine.

Note that the regulation covers all cables (other than ones specifically covered by other standards) - so the requirement applies not just to mains cables but to all types - alarm, TV aerial, data, etc etc as well.
- Andy.
 12 May 2018 07:27 PM
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mapj1

Posts: 10430
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avoid sticky backed mini trunking on the ceiling with no other means of support - used to be common for flats where there is no access from above, and avoid wires over bedroom doorways on the simple one nail and plastic tab style clips.
It does not mean you can't have plastic trunking, just you ought to augment it with some 'catch all' metal clips as well. Wires supported by joists won't fall until there is a far more serious problem.
Apart from that sort of thing, most situations are 'no change'
Note that the regulation covers all cables (other than ones specifically covered by other standards) - so the requirement applies not just to mains cables but to all types - alarm, TV aerial, data, etc etc as well.

I'm sure fire fighters would be delighted if it did, but such installations (along with anything over 1000V, but maybe that's just me) are strictly out of the scope of BS7671, and the same requirement needs mirroring in things like the instructions for telephones, TV installers,folk hooking in speaker cables and so on, as even if we think it was in scope, they don't read the wiring regs.

-------------------------
regards Mike
 13 May 2018 06:43 PM
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AJJewsbury

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I'm sure fire fighters would be delighted if it did, but such installations (along with anything over 1000V, but maybe that's just me) are strictly out of the scope of BS7671

I agree that telephone wiring systems are out of scope (being covered by BS 6701) but I'm not aware of installation standards covering the systems I mentioned. If they aren't covered by any other standard then my understanding was that they'd fall under BS 7671 'by default' (just like any other ELV wiring).
- Andy.
 14 May 2018 02:09 PM
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ben22

Posts: 11
Joined: 26 March 2013

Much appreciated thanks for the advice,
 14 May 2018 04:05 PM
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gkenyon

Posts: 5049
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Originally posted by: AJJewsbury

I'm sure fire fighters would be delighted if it did, but such installations (along with anything over 1000V, but maybe that's just me) are strictly out of the scope of BS7671


I agree that telephone wiring systems are out of scope (being covered by BS 6701) but I'm not aware of installation standards covering the systems I mentioned. If they aren't covered by any other standard then my understanding was that they'd fall under BS 7671 'by default' (just like any other ELV wiring).

- Andy.
This is interesting.

BS 7671 says they are in scope, supplemented by BS 6701. See Regulation 110.1.3.

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
 14 May 2018 04:21 PM
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AJJewsbury

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Good point Graham. My memory seems to have failed after 110.1.2 (iii) - and I now notice that it specifically refers to standards for appliances, so presumably wouldn't include standards for wider systems anyway.
- Andy.
 14 May 2018 08:27 PM
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Dave69

Posts: 707
Joined: 16 July 2011

As a retained fire fighter as well as a sparks I seem to remember that reg is to be replaced by 521.10.202 and that requires all cables to be adequately supported against their premature collapse in the event of a fire.

This applies throughout the installation. Not just in escape routes

As ive said before if the ceiling is plasterboard or lath and plaster etc. it is easy to find the joists above and use standard wood screws through a fire rated clip and drive them through the ceiling into joists, another option is toggle type clips, if the ceiling happens to be concrete its a head scratcher and obviously if its asbestos you leave well alone
 14 May 2018 10:35 PM
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mapj1

Posts: 10430
Joined: 22 July 2004

The idea is a good one, but once this becomes common practice, the remaining problems will be the random string flung in for TV antennas, telephones, ADSL, computer networks etc. Whatever we think, the average hifi enthusiast is not likely to read or follow BS7671, and to be effective the message needs better propagation to reach these areas.

-------------------------
regards Mike
 14 May 2018 11:21 PM
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gkenyon

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Originally posted by: mapj1

The idea is a good one, but once this becomes common practice, the remaining problems will be the random string flung in for TV antennas, telephones, ADSL, computer networks etc. Whatever we think, the average hifi enthusiast is not likely to read or follow BS7671, and to be effective the message needs better propagation to reach these areas.
Indeed, but there's not really any way of "legislating" for "plug and play", or covering in standards, as people will just do what's easiest.

In terms of single dwellings ... it will only be seen as a problem when someone actually gets hurt, but it took many years of plastic cable clips and trunking before Shirley Towers became an issue, and this type of building is of course a different kettle of fish for both firefighters and tenants / homeowners.

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com
 15 May 2018 12:00 AM
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Dave69

Posts: 707
Joined: 16 July 2011

As I've said before coax is probably the worst and double coax even more so, a bit of cat 6 can just about be broken with gloved hands but with coax you have very little chance.
We will never stop the DIYer doing what they want in their home but we can try to educate them. We are asking for diy kits to have clear instructions on how to fix cables. Even cables run across the floor can become trip hazzards and trust me if you to fall over wearing BA it isn't the easiest task to get back up. Remember we are working in extreme heat and near zero visablity, you shuffle your feet to feel for objects and to make sure the floor is safe etc but with boots on you don't feel the telephone extension cable rapping around your foot. But having said that the main concern is cables overhead, too many fire fighters have lost their lives and it has to stop.
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