sizing containment for T&E

[atm84]

Does anyone have experience sizing cable tray/ basket and trunking which is used for twin and earth cabling?

The on site guide only provides guidance and factors where single core PVC cables are used.

I am looking for help where twin and earth is used.

 

[telectrix]

Like I already stated the OSG only provides guidance for single core cables.

so use the same tables. you won't be far out. as to how many cables, basically there should be approx. 50% cable and 50% airspace in the trunking. or.................. when you can't get the lid on, you know it's too full.

 

[Simonslimline]

Like I already stated the OSG only provides guidance for single core cables.

Maybe re read it perhaps!

 

[atm84]

Like I already stated the OSG only provides guidance for single core cables.

so use the same tables. you won't be far out. as to how many cables, basically there should be approx. 50% cable and 50% airspace in the trunking. or.................. when you can't get the lid on, you know it's too full.

How can you use the same tables when its completely different type of cable.

Come on guys do any of you actually carry out design work or do you just guess and hope for the best.

 

[atm84]

Like I already stated the OSG only provides guidance for single core cables. Get your facts right before patronising me.

Maybe re read it perhaps!

Yep re read it. Still says the same. For single core cables

 

[Plonker 3]

Its a generic question. how dies one calculate how many Twin and Earth cables can fit on x size cable tray. Yes I know you can work out the diameter if the cable and multiple, but in reality cables are not butted right up to each other. Is there a factor that is applied.

Well seeing as neither the BGB or OSG have any info regarding this then no there isnt.

 

[atm84]

sizing containment for T&E

Lets hope the New BYB has. But I doubt it.

 

[telectrix]

like i said. use the tables for singles and assume T/E is poorer at heat dissipation due to it's sheath so derate by a factor that you determine using common sense. BS7671 is not the bible.( even if IET think it is)

 

[Simonslimline]

Yep re read it. Still says the same. For single core cables

What book are you reading? My OSG (Green) talks about other sizes and types of cable. Bottom of page 138.

 

[atm84]

like i said. use the tables for singles and assume T/E is poorer at heat dissipation due to it's sheath so derate by a factor that you determine using common sense. BS7671 is not the bible.( even if IET think it is)

Will you please re read the OP. I am not looking for cable size. I'm looking for tray size.

 

[atm84]

Yep re read it. Still says the same. For single core cables

What book are you reading? My OSG (Green) talks about other sizes and types of cable. Bottom of page 138.

I will ask you a very simple question. Does it tell you how to size cable tray for twin and earth cables?

 

[Plonker 3]

Have you ever tried applying common sense and finding out for yourself what you need to know?

 

[Simonslimline]

I was mainly thinking of basket but wondered how trunking would be sized with T&E. I have come across it on some supermarket installs.

You have asked about trunking though.

This is what i was getting at.

 

[atm84]

Have you ever tried applying common sense and finding out for yourself what you need to know?

Yes I have and it didn't get me anywhere.

 

[atm84]

I was mainly thinking of basket but wondered how trunking would be sized with T&E. I have come across it on some supermarket installs.

You have asked about trunking though.

This is what i was getting at.

It still doesn't say what factor to apply to Twin and Earth in trunking does it.

 

[Anthony S]

Have you got a job that need's doing ?

 

[telectrix]

if the cables hang over the sides, it's too small.

 

[Deleted member 72666]

Look! It's really simple, first decide if you're grouping these cables or are they to be spaced? Then measure said cables with or without spacing, choose tray/ basket and determine size and divide this by size and number of cables. It's not hard is it?

 

[VoltzElectrical]

How many cables? More information needed.

Also, @ the earlier posters that poo-pooed the twin and earth in trunking, I have worked on student accommodation where 4x4 trunking run around the ceiling/ wall joint and drops done in mini -trunking, wired in Twin. Also office space where all runs done in twin from DB up into attic space, along tray, boxed in drops in corners to skirting dado, etc..

Making generalisations just shows lack of real life situations.

 

[tazz]

Find this hard to believe....a construction company will have submitted a cable schedule and the design for containment...The normal schedule will always be for lsf singles in supported galv trunking, db armored on tray size to suit quantity plus future additions. And basket suited for data, and basket for fire/security. For all those who keep harping on about escape route containment, this is why designers have chose this method over the past 5 plus years

 

[Risteard]

The normal schedule will always be for lsf singles in supported galv trunking

Agreed. T&E in containment is an appalling practice really.

In fact generally T&E outside of a domestic premises is pretty poor.