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dogman

Cables in Trunking

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Hi 

i a trying to think how to keep the cables tidy going to and from my consumer unit.

The electrician wants to clip them (Visible )to the plasterboard slopping roof in the plant room. Not a big issue but i would like to hide them.

 

options are to create a 25mm cavity between a sheet of osb (over MBC roof) and plasterboard and run in cavity

or

Use maxi trunking and run cables in bunches ie 3 x 6mm and 2 x 2.5mm in a 100mmx50mm 2m length of trunking

 

Any issues with either before i suggest them to Electrician 

 

 

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Service void is the neatest way unless headroom is tight (I avoided a service void in the en-suite to gain every mm of available headroom)

 

If they must go on the surface, trunking is much preferable. Apart from anything else, clipping to plasterboard rarely gives a secure fixing, the nails of most clips are simply too short.

 

Think how it will transition from the sloping ceiling to the upright wall, I assume that has a service void?

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Its a typical Mbc build so all 50mm service voids for walls and 25mm for ceilings 

It would be easiest to use a sheet of OSB on roof and then batten to create the service void.

 

How is the void treated for wiring regulations

 

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yes, but

 

with the amount of insulation the void is sort of filled up

 

 

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You can sort of see what i mean here in one of the bed rooms

2017-08-23_11_08_11.thumb.jpg.ee44c062bd34b8399be671d7415ee48f.jpg

 

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23 minutes ago, dogman said:

yes, but

 

with the amount of insulation the void is sort of filled up

 

 

 

We have exactly the same issue with our MBC ceilings. The insulation pumped in causes the airtight membrane to "pillow" to the point that the ceiling service void isn't much of a void! In the end I counterbattened certain ceiling areas to allow for cable runs. 

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@Barney12 out of interest what is the reference method you have used for twin and earth in the service void of a MBC wall

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Consider future nails tenancy too.

 

I would be attracted by something that let expose the whole caboodle by undoing 4 or 8 screws.

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3 minutes ago, Ferdinand said:

Consider future nails tenancy too.

 

I would be attracted by something that let expose the whole caboodle by undoing 4 or 8 screws.

 

Not hard do. The area above the cu would be a safe zone so no nails in future:$ and using painted MDF screwed to battens would be fine

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A sloping ceiling, is still a ceiling, so cables can run anywhere.

 

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1 hour ago, dogman said:

How is the void treated for wiring regulations

 

Anyone know the answer to how a void is treated?  Does the electrician want to run them up the slopping ceiling and into the first floor joists for a reason and will covering them with a sheet of plasterboard change something? (rating? or circuit length) I have already had to add a couple of extra ring main circuits because of cable length and dont want any more as running out of ways 

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1 hour ago, dogman said:

 

Anyone know the answer to how a void is treated?  Does the electrician want to run them up the slopping ceiling and into the first floor joists for a reason and will covering them with a sheet of plasterboard change something? (rating? or circuit length) I have already had to add a couple of extra ring main circuits because of cable length and dont want any more as running out of ways 

A void in a wall is just like any other wall, cables must run in a safe zone.

 

A void in a ceiling is just like any other ceiling, the whole ceiling is a safe zone. and a sloping ceiling is still a ceiling.

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I plan to mount the CU below a pair of 50X25 battens to allow the cables to run up the wall and then it will get covered with Fermacell to make it look “neat”. It’s a double decker board and there are no downward drops so it’s all up into the ceiling space with the exception of the main SWA and tails. 

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In effect you re making your own bit of trunking, so your electrician just designs it for trunking.

 

 

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10 hours ago, dogman said:

@Barney12 out of interest what is the reference method you have used for twin and earth in the service void of a MBC wall

 

Clipped to the side of the batten. As far back as achievable.

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Not wanting to put a downer on this but imo I don't think the regs have really caught up with "passive" build techniques yet. Such well constructed, vertical cable voids full of cables, sat above a cu are potential chimneys providing a fire route between floors. I'd urge anyone to think about a fire break. Neatly drilled holes in some frpb maybe all sealed with intumescent (touched on in another thread) would be a nod to it.

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8 minutes ago, Onoff said:

Not wanting to put a downer on this but imo I don't think the regs have really caught up with "passive" build techniques yet. Such well constructed, vertical cable voids full of cables, sat above a cu are potential chimneys providing a fire route between floors. I'd urge anyone to think about a fire break. Neatly drilled holes in some frpb maybe all sealed with intumescent (touched on in another thread) would be a nod to it.

Wouldn't just pumping the void at the rear of the CU with B5 F/R expanding foam do the job. The wires aren't going to combust so it'll just be the CU-to-void transit to protect. Having only that to cover won't affect the 'cable in insulation' aspect as it'll only be a short foam 'plug' of around 2-300mm. 

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1 hour ago, Nickfromwales said:

Wouldn't just pumping the void at the rear of the CU with B5 F/R expanding foam do the job. The wires aren't going to combust so it'll just be the CU-to-void transit to protect. Having only that to cover won't affect the 'cable in insulation' aspect as it'll only be a short foam 'plug' of around 2-300mm. 

 

Anything really as long as its something. I've indeed used loads of that pretty pink foam around bfo armoured between floors. Just gets a bit messy when you want to add another cable and you have to dig it out.

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58 minutes ago, Onoff said:

Not wanting to put a downer on this but imo I don't think the regs have really caught up with "passive" build techniques yet. Such well constructed, vertical cable voids full of cables, sat above a cu are potential chimneys providing a fire route between floors. I'd urge anyone to think about a fire break. Neatly drilled holes in some frpb maybe all sealed with intumescent (touched on in another thread) would be a nod to it.

Very true.

 

In fact my own (metal) CU is mounted on the actual inner wall, so when the service void is boxed in, the plasterboard will in effect flush mount the CU leaving just the front showing.  I will be sealing any holes with intumescent sealant.

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Could you just run a length of intumescent seal around the mounting board. It should allow air flow and adjustments but protect if there is flame 

 

 

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17 minutes ago, dogman said:

Could you just run a length of intumescent seal around the mounting board. It should allow air flow and adjustments but protect if there is flame 

 

 

 

I'm guessing you've the mounting board spaced off the wall with the cables going through then up behind the board? If so go for it.

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Just now, Onoff said:

 

I'm guessing you've the mounting board spaced off the wall with the cables going through then up behind the board? If so go for it.

 

Yes that's the plan.

I'm doing the installation of the wood board and trying to ensure all the cable routes are accessible to cut down of time on site.

 

 

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46 minutes ago, dogman said:

 

Yes that's the plan.

I'm doing the installation of the wood board and trying to ensure all the cable routes are accessible to cut down of time on site.

 

 

 

It'll be a pita if you were to neatly clip everything then board over with something immovable only to find you need to run another cable. You end up with that one "dangler" as reminder everytime you look up ! :) You could run a bunch of plastic conduits (plus spares) like pan pipes, flat to the surface just to act as guides and board over them. (As its up slope it'll offer more support). Have the spare tubes nominally in line with the spare breakers.

 

Had no choice here but to hack a section out (all neatly repaired) to tidy up the existing cable lay and run new. 

 

P2060131_zpscc106965.thumb.jpg.d2045bf16f26062c22cb25cb95fa27bf.jpg

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Any route between floors is still a potential fire /smoke route for sources other than the cu don't forget.

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