twin and earth cabling size for commercial buildings

[Lister1987]

Being commercial, will it be open to public? If it is then isn't thr consensus to use FP or similar?

 

[Risteard]

Hi, from Amtech cable calculations, the cpc is usually less than that you would usually use in an installation. For example, if you use singles then you would use the same size cpc as the live and neutrals, but on calculations it usually can be less. Not every case but usually

Yes I agree that it often can be depending on fault current and disconnection time, but it remains a poor cable choice.

 

[default]

Being commercial, will it be open to public? If it is then isn't thr consensus to use FP or similar?

No

 

[default]

Probably Building Regs may apply if the cable is run in the cavity. Then get some polystyrene pumped in to help migration.

What

 

[Dustydazzler]

When I first started out it was a lot of over night shop fitting stuff and cut and shut office re-furbs. We used A LOT of LSF twin and earth and 3c or earth and lots of white and red FP cable to modift circuits.

Only when time and budget allowed did we put up galv conduit Or galv trunking work and wire in singles, which wasn't that often sadly

 

[Vortigern]

Why not? If T&E is suitable for the job why not use it?

As stated in my post. I am not saying dont/cant use it just expressing what I consider good design and good looking installation that is robust and easily changed, shows damage immediately, is easier to fault find on etc. Putting T&E in the fabric of the building without trunking (as the OP states) clipped (?) just seems to me poor design imho that is all I am saying. As a matter of fact I am just doing a commercial in T&E as the situation necessitates it, but not my first choice by any means. The other thing about is the whole first fix, second fix is not a big thing fitting in between framers, chippies, plasterers and plumbers etc. That whole process is a lot less complex. And don't get me started with the boarders/plasterers rather than pull the light switch wire into the hall by the door they stuffed it through the other wall in the far corner of the bedroom and other things!

 

[nicebutdim]

When I first started out it was a lot of over night shop fitting stuff and cut and shut office re-furbs. We used A LOT of LSF twin and earth and 3c or earth and lots of white and red FP cable to modift circuits.

Only when time and budget allowed did we put up galv conduit Or galv trunking work and wire in singles, which wasn't that often sadly

OP is a design consultant and, as such, it is up to them to specify as they see fit.

While T&E might be an option, it's one that neither customer nor installer will thank them for when it comes to any future additions. I guess there are times when customers will be intransigent where price of materials are concerned, but I'd much rather see designers lead customers toward sensible solutions for their premises and not simply specify on the basis of price.

Additions can often be problematic, but it's not a great feeling when faced with a job made unnecessarily difficult at the design stage.

 

[Dustydazzler]

This is where the Yanks have one over on us, in commercial sites over there you aren't allowed to use soft skin cable up in the voids or under the floors. It has to be in galv flexi or galv Emt. It is not acceptable to lash in twin and earth over there, twin and earth ( romex ) is just for domestic

 

[Vortigern]

I'm pretty sure a lot of us can produce a much neater and more elegant installation with T&E

I am sure we could, funny thing is I have never seen it where T&E is concerned. Just loadsa cables thrown over suspended ceilings, lights and mixed with data cables all over the show. But then I have worked on conduit, galv and pvc looks immaculate virtually everytime. And I have looked above a lot of suspended ceilings.

 

[Dustydazzler]

I am sure we could, funny thing is I have never seen it where T&E is concerned. Just loadsa cables thrown over suspended ceilings, lights and mixed with data cables all over the show. But then I have worked on conduit, galv and pvc looks immaculate virtually everytime. And I have looked above a lot of suspended ceilings.

Things is usually the glav conduit installed neatly saddled up to the concrete ceiling is installed before the drop ceiling grid went up. The t&e and data wires all lashed in is thrown above the ceiling at a later date by every tom dick and harry who has worked on the site

 

[davesparks]

Being commercial, will it be open to public? If it is then isn't thr consensus to use FP or similar?

Not quite, I think you may be thinking of LSF/LSOH type cables. LSF T&E exists.

 

[davesparks]

Clipped in a cavity, doesn't sound right. Think the installation method needs looking at a bit more closely.

Why not? What's wrong with cables being clipped in a cavity?

 

[Electro-tech]

Why not? What's wrong with cables being clipped in a cavity?

Depends on the purpose of the cavity & what else will end up in there, other than a cable route. Especially an external cavity wall.

 

[nicebutdim]

Depends on the purpose of the cavity & what else will end up in there, other than a cable route. Especially an external cavity wall.

To be fair to the OP, their comments indicate partition walls and not external cavities in which it would be nigh on impossible to clip cables.

 

[default]

To be fair to the OP, their comments indicate partition walls and not external cavities in which it would be nigh on impossible to clip cables.

Can it still be classed as clip direct. Maybe reference method G?. And if they're stud walls off the outer block work there's Surely going to be insulation.

 

[nicebutdim]

Can it still be classed as clip direct. Maybe reference method G?. And if they're stud walls off the outer block work there's Surely going to be insulation.

OP stated internal walls with no thermal insulation.

 

[default]

OP stated internal walls with no thermal insulation.

Still can't be classed as clipped direct. It's in a wall.

 

[cireland]

There is no exact reference method for this but I'd say clipped direct is closest.

 

[default]

Still can't be classed as clipped direct. It's in a wall.

And

There is no exact reference method for this but I'd say clipped direct is closest.

I'd say 103. If there's an EICR done in the future they either won't have the original test to go by or they'll look at it and think who ever tested it put down the wrong classification. I do sometimes think the installation references could do with one or two more. C'est La Vie

 

[cireland]

103 is with thermal insulation which greatly de-rates the cable.