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probably an easy answer if you know it, unfortunately I don't (or just cant bloody remember)... but how do you work out cable sizes when using more than one conductor?

Basically, and I wont go into specifics, but there's been a lovely cock-up by the ground workers and instead of putting in a nice size duct for me, they've put in multiple small ducts, meaning I'm going to have to install multiple SWA's

Is it a simple case of the rating of a single cable (with normal correction factors applied) and multiple it to reach total loading requirement. Or what?

ie. if a 4mm SWA is capable of carrying 25amps over the distance, will 4x 4mms be capable of 100amps?
 
probably an easy answer if you know it, unfortunately I don't (or just cant bloody remember)... but how do you work out cable sizes when using more than one conductor?

I can’t remember (can’t be bothered to look) how to do your work for you.

I can forward my scale of fees for consultancy work.
 
probably an easy answer if you know it, unfortunately I don't (or just cant bloody remember)... but how do you work out cable sizes when using more than one conductor?

Basically, and I wont go into specifics, but there's been a lovely cock-up by the ground workers and instead of putting in a nice size duct for me, they've put in multiple small ducts, meaning I'm going to have to install multiple SWA's

Is it a simple case of the rating of a single cable (with normal correction factors applied) and multiple it to reach total loading requirement. Or what?

ie. if a 4mm SWA is capable of carrying 25amps over the distance, will 4x 4mms be capable of 100amps?


More to the point, will the points of connection at each end of the cable be suitable for multiple conductors?? No need for correction factor relating to number of cables, as all the parallel cables of a circuit are classed as a single cable, much like a RFC.
 
Noooo! lol
Oh dear E54 you have started it now, I remember the long...long thread the last time this came up. lol

I am staying out of it lol
 
Ah. Can someone point me in the direction of the long thread then :)
connection points aren't an issue. I'm purely trying to confirm the cable calls and sizes. It's been a long, long time since I've had to consider it, that's all
 
It was said tongue firmly in cheek, lol

Because we ended up with long theories about thermal transfers and god knows what else, partly caused by the reg book tables and definitions etc..ad nauseum lol
 
Mmmmm thermal transfers, think I'll keep away from that, that really is going back to college/uni days... Lol
i was particularly keeping away from asking anyone to do the calcs for me. Just someone to point me in the right direction before I try and dig out my 15th edition and search through my notes stuck inside the back cover :)
 
Reading that thread you will use up time you will never get back lol

It was partly down to the regs derating factors for parallel supply cables argued in favour of by some knowledgeable chaps on here, but on the other hand dismissed by some other equally knowledgeable chaps on here.

Both sides made some good points, me ? I have never had to do the calcs for the size of cables in that thread, if it was smaller sizes I think I would probably err on the side of the regs, the larger sizes I would probably have to get help from someone who deals with that size of cable regularly.
 
It was said tongue firmly in cheek, lol

Because we ended up with long theories about thermal transfers and god knows what else, partly caused by the reg book tables and definitions etc..ad nauseum lol

I just found it quite amazing that anyone would even consider using a grouping factor on what is a single circuit... No-one ever did post a link to any of the other international standards that supposedly added a grouping factor to a parallel single circuit. I know they don't anyway, because i bloody well use many of those standards on my projects!!

All i can say is, there must be some pretty ''hot'' parallel circuits that i've left up and running around the world, one or two with in excess of 10 single conductors per phase. Now run that through a grouping factor table, and you'll see just how bloody daft things will get!! lol!!
 
probably an easy answer if you know it, unfortunately I don't (or just cant bloody remember)... but how do you work out cable sizes when using more than one conductor?

Basically, and I wont go into specifics, but there's been a lovely cock-up by the ground workers and instead of putting in a nice size duct for me, they've put in multiple small ducts, meaning I'm going to have to install multiple SWA's

Is it a simple case of the rating of a single cable (with normal correction factors applied) and multiple it to reach total loading requirement. Or what?

ie. if a 4mm SWA is capable of carrying 25amps over the distance, will 4x 4mms be capable of 100amps?


The easy answer to your question is read appendix 10 of BS7671: overcurrent protection of cables in parallel.
Spoiler: it says sum the CCCs!

and just for contention it also says apply appropriate grouping and other factors!
Though appendix 4 tangentially mentions that the number of cables equals the number of circuits!
 
I just found it quite amazing that anyone would even consider using a grouping factor on what is a single circuit... No-one ever did post a link to any of the other international standards that supposedly added a grouping factor to a parallel single circuit. I know they don't anyway, because i bloody well use many of those standards on my projects!!

All i can say is, there must be some pretty ''hot'' parallel circuits that i've left up and running around the world, one or two with in excess of 10 single conductors per phase. Now run that through a grouping factor table, and you'll see just how bloody daft things will get!! lol!!

Now now eng54. I know its Monday morning but there is no need to be nasty. :)
I am grateful that you and Rockingit helped me out there. Especially Rockingit for finally commenting on why grouping factors are not required for a single circuit.
 
Now now eng54. I know its Monday morning but there is no need to be nasty. :)
I am grateful that you and Rockingit helped me out there. Especially Rockingit for finally commenting on why grouping factors are not required for a single circuit.

Eh, ...Please point out to me, exactly where i am getting ''Nasty''??? :)
 
Now now eng54. I know its Monday morning but there is no need to be nasty. :)
I am grateful that you and Rockingit helped me out there. Especially Rockingit for finally commenting on why grouping factors are not required for a single circuit.


That's handy - there was me, all this time, fully unwinding my extension lead to feed my 3 bar fire!
 

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