Cable in steel conduit

[diyhell]

I notice ban-all-sheds in another post mentioning that you shouldn't fill conduit or trunking more than 45%, IIRC.

Does this mean the 1.5mm T&E (and 1mm 3C & E) in the steel conduit that holds my lighting circuit is dodgy?

Uh oh. And I thought my electrical jobs were over

Looks like I'd better go and work out the area of the conduit versus the cable. Pi R Squared blah blah.

Any thoughts?

 

[ryanj]

What size of conduit is it?

If it is a properly designed conduit system, you could install singles into it.

 

[diyhell]

What size of conduit is it?.

1/2 inch

If it is a properly designed conduit system, you could install singles into it .

Very true. But given the low wattage, is likely to be unsafe?

I can deal with the embarrassment of a badly designed system but not an unsafe system...

 

[plugwash]

i think the 45% is only a guideline and i think its partly to make pulling the cables in easier

also bearing in mind that in a lighting cuircuit the breaker reating is usually at least a factor of 2 smaller than the cable rating its really not something i would worry about

 

[diyhell]

Ah, now that's the answer I want to hear Plugwash

A temporary respite before I get the p**s taken out of me by my sparky colleague who's going to test the system...

 

[breezer]

A temporary respite before I get the p**s taken out of me by my sparky colleague

well dont tell him its 1/2 inch conduit then (it doesnt exist) its probably 20mm.
the space is nothing to do with pulling in cables, its to do with heat disipation. it allows air to be able to circulate around the cables, if they were compressed they would get very hot / melt.

a similar thing is an extension lead it should be used fully unwound if used for its amx rating, if not it will melt / get warm

 

[andy]

av seen worse. 2 2.5mm t+e in 20mm steel conduit... and only wired into a school last year. b/c of it, it had to be re-wired again

 

[diyhell]

15mm must have been thinking of the copper tubing in which I ran the 10mm2 cooker radial

 

[andy]

copper? u mean water pipes?

 

[securespark]

the space is nothing to do with pulling in cables, its to do with heat disipation. it allows air to be able to circulate around the cables, if they were compressed they would get very hot / melt.

Precisely. A sort of guard against "grouping".

 

[diyhell]

copper? u mean water pipes?

Just joking

 

[Damocles]

circulating water around the cables would be much better for cooling them than free air. Never heard of water cooled computers?

 

[plugwash]

you would have to be carefull about the insulation material though some things don't respond well to constant immersion

 

[Damocles]

yep. Isn't that why they filled supply transformers with PCP oil? Doesn't conduct. Just highly poisonous and practically indestructible.

(think it was PCP? anyway, definitely poisonous)

 

[ban-all-sheds]

PCB - Polychlorinated Biphenyls - nasty stuff....