Plastic compression glands for T&E into metal CU

[Pat H]

I'm sure this will have come up but what are the thoughts on cable entry into metal CUs?
Obviously from the rear is simplest but if cables have to come in from below then do we need to use metal glands or are plastic ok?
I assume for RFC its best for both legs of the circuit to enter together (although I think in terms of eddy currents as long as the L & N in the T&E are together that's all that's needed)

Been talk of ensuring the fixings to the wall are fire proof but even if use plastic raw plugs the screws are metal and I can't see a box falling off if it got really hot.
Also thinking some Intumescent sealant around the back to help seal the rear entry cables will effectively glue it in place anyway!

(Hey spelt topic right this time

 

[sparksburnout]

What is it about a straightforward task like fitting a metal CU that causes soo.. many problems, is it just me.

No

 

[westward10]

Makes me want to weep.

 

[Leesparkykent]

Oh for goodness sake this is ridiculous. The document is referring to cable systems in mostly non-domestic situations where fire fighters have been trapped by cables collapsing into fire escape routes, not domestic CU's falling off the wall!!

Yeah I was just pointing out the document which refers to the premature collapse due to wall plugs, so they might not be as robust in the event of a fire as you think.

 

[sparksburnout]

Makes me want to weep.

Don't worry about the IR values, continuity, CPC's in lighting circuits, Earthing, Bonding, labelling, discrimination, accessibility, neatness or other quality of workmanship, or all that nasty paperwork and stuff, just make sure the bloody things rammed onto the wall with at least 4 coach bolts.

 

[Harwoodandy]

What is it about a straightforward task like fitting a metal CU that causes soo.. many problems, is it just me.

No its not.

I think there is a certain amount of blindness and distraction in "being compliant" that results in the obvious being overlooked. Would any domestic scheme even examine the means of fixing a CU to a wall? I think not, hopefully they would be more interested in the installers competence at not electrocuting somebody or causing a fire hazard in the first place.

 

[Pete999]

http://i.stack.Upload the image directly to the thread.com/ou9oP.jpg

Yes OK

 

[Pat H]

No its not.

I think there is a certain amount of blindness and distraction in "being compliant" that results in the obvious being overlooked. Would any domestic scheme even examine the means of fixing a CU to a wall? I think not, hopefully they would be more interested in the installers competence at not electrocuting somebody or causing a fire hazard in the first place.

That is true. The whole point metal enclosures have come in is due to shoddy installation and DIY work. Those folks won't give a hoot about the regs and will do whatever they want so the risk there is no less.
But at least having regs in place means that when it does go wrong its easier to pull them to account.
So as you say a well done installation shouldn't catch fire anyway so why need a metal enclosure even? But what if a year down the line a DIYer adds an additional circuit and leaves the screws loose to the feed to their new hot tub?
Its not just our work then ant there that matters its what happened later as well. I'll be using metal fixings anyway. So if you come across a CU fixed with metal fixings it will be one of mine as I'm the only one doing it

 

[Midwest]

Dear oh dear. How do we get from a CU to made of a non combustible material or installed in a non combustible cabinet or enclosure, i.e. reg 421.1.201, to a CU that contains a fire, should be sealed with intumescent material and fixed with non melting fixings. The whole point of 421.1.201 was to remove a source of fuel (the plastic enclosure) from any possible fire. Next someone's gonna suggest metal MCB's.

You just saying this to take my mind off Trump

 

[charlie76]

Let me know if you find some metal rawl plugs

Eddy currents on a SP&N CU Get real

These are available, we use them regularly in fire alarm installations for cables passing through escape routes.

 

[charlie76]

Next someone's gonna suggest metal MCB's.

Well since you mention it I have been putting intumescent sealer all over the back of MCB's to ensure that a fire is well contained within the consumer unit. I am currently working on a miniature fire suppression system to discharge FE227 into the consumer unit when the internal fire alarm system in the unit detects smoke. I am also considering fire shutters to the front face, belt and braces and all that. And before someone thinks I am cutting corners, a smoke extract system has been installed within the consumer unit.

 

[NDG Elecs]

I posted a link to that BRE test a few weeks back in another post. I posted it in response to a post by Westward saying that he thought it unlikely that plastic wall plugs would melt in a masonry wall. I was of the same opinion too until I read through the report. OK, it deals with cable supports specifically, but the same melting could possibly occur elsewhere.

I agree partly with SBO that a consumer unit is not going to fall off a wall in any hurry, and that in all probability for a CU to fall off the fire would have to be pretty bloody intense.

But, a lot of folk on here harp on about good workmanship, and when I posted a few weeks back that was why.

If I go back three years ago I would have never thought of installing metal fire clips like I do now. And I am starting to think the same way in relation to my use of plastic wall plugs. Good workmanship and practise evolves and changes..

 

[NDG Elecs]

Well since you mention it I have been putting intumescent sealer all over the back of MCB's to ensure that a fire is well contained within the consumer unit. I am currently working on a miniature fire suppression system to discharge FE227 into the consumer unit when the internal fire alarm system in the unit detects smoke. I am also considering fire shutters to the front face, belt and braces and all that. And before someone thinks I am cutting corners, a smoke extract system has been installed within the consumer unit.

I use the Aico Nano range.... Interlinked and only 35mm diameter! But fiddly to terminate though...

 

[Midwest]

Well since you mention it I have been putting intumescent sealer all over the back of MCB's to ensure that a fire is well contained within the consumer unit. I am currently working on a miniature fire suppression system to discharge FE227 into the consumer unit when the internal fire alarm system in the unit detects smoke. I am also considering fire shutters to the front face, belt and braces and all that. And before someone thinks I am cutting corners, a smoke extract system has been installed within the consumer unit.

Sarcasm is the lowest form of wit.

 

[Midwest]

If I go back three years ago I would have never thought of installing metal fire clips like I do now. And I am starting to think the same way in relation to my use of plastic wall plugs. Good workmanship and practise evolves and changes..

I was watching one of those Elex show vids, where the subject of cables and clipping was discussed, specifically in a domestic environment. For example, someone in the audience asked how you could achieve this in a rewire in a domestic property, say where the floor above was a tiled floor in a bathroom., preventing access to clip the new cables.
Elecsa were of the opinion, that the 30min fire protection afforded by the plasterboard, was sufficient to comply with 521.11.201.
Napit disagreed, and said in the spirit of the reg, once the 30min has elapsed, the non clipped cables would be of a danger to the fire fighters.

Work that one out! Sorry Madame, it's either ceiling down or your new floor up.

 

[Nickj]

I was watching one of those Elex show vids, where the subject of cables and clipping was discussed, specifically in a domestic environment. For example, someone in the audience asked how you could achieve this in a rewire in a domestic property, say where the floor above was a tiled floor in a bathroom., preventing access to clip the new cables.
Elecsa were of the opinion, that the 30min fire protection afforded by the plasterboard, was sufficient to comply with 521.11.201.
Napit disagreed, and said in the spirit of the reg, once the 30min has elapsed, the non clipped cables would be of a danger to the fire fighters.

Work that one out! Sorry Madame, it's either ceiling down or your new floor up.

It is interesting that even the schemes can't agree. The regulations or guidance notes should spell things out more clearly.

The less floors you have to lift the better. I wouldn't lift floors to fire clip escape routes and take the same view as elecsa that the ceiling provides enough protection but I do see napits point of view...I don't think the ceiling utterly fails after 30 minutes...therefore surely cable would be supported by the remaining ceiling for much longer...

 

[Sparks999]

The requirement is for the enclosure to be flame retardant, no mention is made of the cable entries. If you use stuffing glands with T&E you should really replace the rubber inserts with those that have oval holes through them. T&Es on ring finals can pass through separate entries. Wouldn't be worrying about using plastic wall plugs.

Just did an EICR on a 3 phase DB that had feeds from the board all exit together through a bush and lockring, go to a rotary isolator mounted to the trunking next to the board and then the loads from the rotary’s passed through a different bush in the board and to a seperate bit of containment. The cables are 4mm or 6mm twin and earths supplying 4 32A SP commando sockets would this be an issue with eddys?

 

[littlespark]

Just did an EICR on a 3 phase DB that had feeds from the board all exit together through a bush and lockring, go to a rotary isolator mounted to the trunking next to the board and then the loads from the rotary’s passed through a different bush in the board and to a seperate bit of containment. The cables are 4mm or 6mm twin and earths supplying 4 32A SP commando sockets would this be an issue with eddys?

Not if the L and N of the same circuit run through the same bush…. Which they would, if all t&e.

 

[Sparks999]

Not if the L and N of the same circuit run through the same bush…. Which they would, if all t&e.

Thanks I did think that I just remember being told years ago at college you have to bring both of the legs of a ring through the same hole so wasn’t 100% sure

 

[davesparks]

Thanks I did think that I just remember being told years ago at college you have to bring both of the legs of a ring through the same hole so wasn’t 100% sure

You don't need to bring both legs of a ring through the same hole, that's nonsense.