whats the requirement on cable tray going in riser cupboards

[sparkidave63]

Hi Guys
I have a block of 9 flats 3 floors ,ground ,1st & 2nd.6" cable tray going from top to bottom x2 .LV and HV.The contracts manager is insisting on the tray stopping between floors and a 4" pipe with a fire collar around it to go through the flooor.Is this correct.
Please help!!!!

 

[James]

There should be some fire protection, as the cables pass through fire barriers, I.e. a floor.
There are other products as well, might not have to be a 4 inch pipe.

 

[davesparks]

Do what it says on the drawings, someone should have designed this.

 

[Ian1981]

Sounds about right if you’re breaching floors

 

[Midwest]

Place I work at, has risers for services.

Found it odd, that they were open between floors. However, having done a bit of research, it would appear they have been designed as 'Protective Shafts'. Have a look at AD B, section B3 page 76. The shaft is designed to prevent spread of fire, and the openings to each floor, have fire doors.

But there doesn't seem the requirement to close of, between floors. Appears the shaft is one compartment. No different to stairs if you think about it.

 

[snowhead]

Firstly if that's what the Contracts Manager is asking for, then that's what you'll probably end up fitting.
As per Davesparks what do your drawings and or spec say about it?
Has the Contracts Manager got Specs he can show you?

What you have to remember is we are post Grenfell and although the new regs aren't out yet everyone will want to make sure they don't have to come back later and upgrade everything.
And they also don't want to end up in Jail, as hopefully some of the Grenfell designers, installers etc will do.

 

[Leesparkykent]

We normally run the tray all the way up then the builder cuts a fire batt around it and seals that with intumescent mastic

 

[sparkidave63]

Firstly if that's what the Contracts Manager is asking for, then that's what you'll probably end up fitting.
As per Davesparks what do your drawings and or spec say about it?
Has the Contracts Manager got Specs he can show you?

What you have to remember is we are post Grenfell and although the new regs aren't out yet everyone will want to make sure they don't have to come back later and upgrade everything.
And they also don't want to end up in Jail, as hopefully some of the Grenfell designers, installers etc will do.

yer thats why i think its a bit of a grey area at the mo. thanks.
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We normally run the tray all the way up then the builder cuts a fire batt around it and seals that with intumescent mastic

thats what ive always done in the past. thanks

 

[westward10]

It isn't a grey area at all. Some risers have no floor between levels and as long as suitable fire doors are fitted and signed as to their purpose it is a protected compartment. Floors may be in place at each level either for convenience to stop you falling down it or that it is a protective measure. Cavity floors can promote the spread of smoke and these cavities often meet with the riser for the distribution of services hence protection is put in place.

 

[Simon47]

The contracts manager is insisting on the tray stopping between floors and a 4" pipe with a fire collar around it to go through the flooor.Is this correct.

My first thought is that no, this isn't the correct approach.
As others have said, it may be a protected compartment, but even then I'd personally go with the belt & braces approach and firestop between floors as well - after all, just because all the doors are fire doors, doesn't stop someone ignoring the notices. A 4" pipe is a poor choice for this - it will be open and allow smoke through until the collar expands and blocks it off.
A better approach is as Leesparkykent says, run the cable tray all the way, then "someone" puts a tray across the riser with a gap where the tray is. The tray will itself be a fire break (either itself non-flammable or carrying something like intumescent material), leaving a gap around the cable tray to allow the installation/maintenance of cabling. When cabling is complete, the gap round the cable tray & cables will be packed with intumescent mastic or socks - socks are best for allowing further work as they can be easily removed and replaced. Something "solid" merely encourages people tasked with installing a cable at minimum cost to just hack a hole and not fix it when they've done.
At a previous job, doing in-house work, I'd put a length of galv trunking through walls and it would be "built in". I'd run my networks cables through and fit an intumescent sock - removing it when I needed to run further cables and refitting it when done. The galv trunking gave me a smooth hole to slide the sock into and be able to get it out again.

For anyone not familiar with the term, intumescent materials (mastic, putty, paint, foam) expands massively when exposed to heat/fire and thus seals up any holes. So an intumescent pad/sock stuffed in a steel trunking through a fire barrier will, if there's a fire, expand fully and completely seal the trunking.

 

[Midwest]

Think someone other than the contracts manager and us, should decide on the specification for the service shaft. If its not been designed as a protective shaft, then perhaps a fire barrier between floors might be necessary.

However, as I said before a stairwell doesn't have fire barriers between floors.