Cable fixings, ceiling new regs.

[Russell griffiths]

So new regs cables fitted overhead need to have a fire proof fixing to stop the cables drooping and entangling a firefighter. 

I get that bit ok. But can someone go into more details or tell me where to look. 

I need to understand what they are trying to achieve so I can understand how to achieve it. 

 

I have a couple of scenarios I hope you can answer. 

 

Lets say you have first floor i joists with holes drilled in the webs, cables run through the holes from joist to joist.   Is a metal fixing required??

 

Lets say you have first floor i joists, cables run  parallel with the joists. Is metal fixing required??

 

lets say you have a false ceiling creating a service void. 50x50 timber used to create the false ceiling, cables are run over the top of the timbers, timbers spaced at 600mm. Is a metal fixing required??

 

all areas I have mentioned have a plasterboard ceiling below them, what I’m trying to get my head around is using a fire proof fixing is cool but screwing it into timber defeats the object if the timber burns, is it basically if the fireman has to pull the ceiling down to get at the fire they don’t want cables entangling them as they go about their job. 

[ToughButterCup]

I hope this helps you to stop overthinking old fella......?

[Oz07]

I wouldn't imagine this applies in domestic ceiling void environments. Check with an up to date sparky by all means but it wouldn't be keeping me awake at night.

[Jeremy Harris]

The regs don't specify a specific solution, all they say is this:

 

Quote

521.10.202  Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire.

 

NOTE 1: Wiring systems hanging across access or egress routes may hinder evacuation and firefighting activities.
 
NOTE 2: Cables installed in or on steel cable containment systems are deemed to  meet the requirements of this regulation.
 
NOTE 3: This regulation precludes, for example, the use  of non-metallic cable clips or cable ties as  the sole means of support where cables are clipped direct to exposed surfaces or suspended  under cable tray, and the  use of non-metallic cable trunking as  the sole means of support of the cables therein.

 

NOTE 4: Suitably spaced steel or copper clips, saddles or ties are examples that will  meet the requirements of this regulation.

 

The ordinary plastic cable clips don't meet this requirement, but metal ones, like these, do: https://www.screwfix.com/p/schneider-electric-thorsman-fire-cable-clips-for-twin-earth-cable-1-2-5mm-silver-100pk/767gv

 

 

[Jeremy Harris]

3 minutes ago, Oz07 said:

I wouldn't imagine this applies in domestic ceiling void environments. Check with an up to date sparky by all means but it wouldn't be keeping me awake at night.

 

The change was introduced after two fire fighters died having got tangled up in  wiring that had fallen down within a block of flats, I believe.  These regs do apply to domestic installations, wherever there may be a risk of cables falling down from above in a fire.

[nod]

One of the Eletricians would know

but I know all the commercial buildings have the cabling run in baskets 

[Oz07]

Exposed surfaces does this mean wires below a plasterboard ceiling as you often see in communal areas of flats from retrofit wiring bits and pieces etc?

[Jeremy Harris]

11 minutes ago, Oz07 said:

Exposed surfaces does this mean wires below a plasterboard ceiling as you often see in communal areas of flats from retrofit wiring bits and pieces etc?

 

 

It's mainly going to be retrofit stuff, I suspect, as it's not hard to put cable runs in through floors where there isn't a risk of the cables dropping before the floor comes down.  You can get metal clips to fit inside plastic trunking to hold cables up if the trunking melts.   Not sure about cables just laid on top of a plasterboard ceiling, though.  My view would be that they need fire resistant support now, mainly because I suspect that water from hoses may bring plasterboard down.

[andyscotland]

59 minutes ago, Russell griffiths said:

 

 

There are varying interpretations among electricians so the first question is what does the spark that will be signing it off (if any) think the regs mean?

59 minutes ago, Russell griffiths said:

So new regs cables fitted overhead need to have a fire proof fixing to stop the cables drooping and entangling a firefighter. 

I get that bit ok. But can someone go into more details or tell me where to look. 

I need to understand what they are trying to achieve so I can understand how to achieve it. 

 

I have a couple of scenarios I hope you can answer. 

 

Lets say you have first floor i joists with holes drilled in the webs, cables run through the holes from joist to joist.   Is a metal fixing required??

 

I would say no : the only way they could drop is once the joist fails. That is not "premature" : at that point the building is structurally unsound and any emergency services will be withdrawn anyway.

 

59 minutes ago, Russell griffiths said:

Lets say you have first floor i joists, cables run  parallel with the joists. Is metal fixing required??

 

I'd say yes, plasterboard may be dislodged during firefighting operations (by water as Jeremy says, or pulled down to access/check for fire in the ceiling cavity). Which would leave these cables and clips exposed.

 

59 minutes ago, Russell griffiths said:

lets say you have a false ceiling creating a service void. 50x50 timber used to create the false ceiling, cables are run over the top of the timbers, timbers spaced at 600mm. Is a metal fixing required??

 

I'd say no, as option one if the 50*50 timber itself is burned through then you're well beyond "premature" collapse.

 

Firefighters may remain if small bits of plasterboard are falling/being pulled down but if whole sheets are dropping off the ceiling complete with their battens that's a very different situation.

 

59 minutes ago, Russell griffiths said:

all areas I have mentioned have a plasterboard ceiling below them, what I’m trying to get my head around is using a fire proof fixing is cool but screwing it into timber defeats the object if the timber burns, is it basically if the fireman has to pull the ceiling down to get at the fire they don’t want cables entangling them as they go about their job. 

 

The concern is primarily surface mounted cables / trunking systems. You're right to consider fixing though - a metal clip in a plastic rawlplug is likely to fail early in a fire. But a metal fixing direct into structural timber is not a concern as it will survive at least as long as the timber (and therefore the structure) itself.

[andyscotland]

31 minutes ago, Oz07 said:

Exposed surfaces does this mean wires below a plasterboard ceiling as you often see in communal areas of flats from retrofit wiring bits and pieces etc?

 

Yes these are the major concern, it's specifically installations like this that caused the firefighter entanglements/fatalities that led to this reg.

[Russell griffiths]

Thanks all , I think that clarifies what I was thinking. 

[Pocster]

I had this concern also . My sparky did conclude that if a timber frame is burning then you shouldn’t be worrying about cabling but need to get out . So I have just metal ties screwed to the timber supporting cables . He was happy with that . 

[Pocster]

Here’s what I used 

 

https://www.screwfix.com/p/ced-galvanised-all-round-band-12mm-x-10m/18298

[Adam2]

Interesting to see a product in this area on dragon's den. Think it was a plastic/polymer combo fired from a gun over the cable. Looked a fast way to install. BUT their claim seemed to be that by being non metal (some polymer IIRC was used for the pins) it was safer!!! Of course the dragons didn't have the building insight to challenge any of that. Though I don't think they got funded. Ahh here is their website https://www.graysclip.com/

Not sure if these would be safe in the above fire safety scenarios