Cable amps for multiple single core in one conduit

Thread Starter

meowsoft

Joined Feb 27, 2021
494
Do you think I needs derating for 4x individual cable in one pipe conduit in three phase system ?, is I needs spacing for same amperage ?
1x35mm amperage is 208a, but 4x35mm amperage 137a, load is only about 100a maximum
And do you think I needs derating for ground cable inside pipe ?, rated is lower when in air (1x35mm2 is 169a, 4x35mm2 is 140a), rated from manufacture is only available in air and ground, no in pipe tables
 

MisterBill2

Joined Jan 23, 2018
9,792
If the "ground" is the required safety ground then under normal conditions it is not carrying any current and so it does not need to be considered for any heating issues.
Is the pipe (conduit) in air or is it in the ground? I do not recall seeing any current rating for conductors in conduit, only about the number of conductors and the portion of conduit filling.
 

Thread Starter

meowsoft

Joined Feb 27, 2021
494
If the "ground" is the required safety ground then under normal conditions it is not carrying any current and so it does not need to be considered for any heating issues.
Is the pipe (conduit) in air or is it in the ground? I do not recall seeing any current rating for conductors in conduit, only about the number of conductors and the portion of conduit filling.
Pipe is put inside ceiling and have limited air circulation (both end of pipe isnt sealed)
But neutral is I think always carry current, because all load is single phase no three phase load, because regulation is limit all electricity contract to 1x100a for single phase, more than 22kva should be used three phase transformer (by regulation)
 

MisterBill2

Joined Jan 23, 2018
9,792
Pipe is put inside ceiling and have limited air circulation (both end of pipe isnt sealed)
But neutral is I think always carry current, because all load is single phase no three phase load, because regulation is limit all electricity contract to 1x100a for single phase, more than 22kva should be used three phase transformer (by regulation)
Neutral and "ground" are very different circuits and functions. Around here the inspectors demand white for neutral and green for ground. And I had not seen a mention of neutral for a while.
 

BobaMosfet

Joined Jul 1, 2009
1,896
Do you think I needs derating for 4x individual cable in one pipe conduit in three phase system ?, is I needs spacing for same amperage ?
1x35mm amperage is 208a, but 4x35mm amperage 137a, load is only about 100a maximum
And do you think I needs derating for ground cable inside pipe ?, rated is lower when in air (1x35mm2 is 169a, 4x35mm2 is 140a), rated from manufacture is only available in air and ground, no in pipe tables
What does the electrical code in your area say- that is your reference, for liability & safety reasons- not opinion from this forum. Electrical wiring from your electrical code will take into account thermal transfer of energy according to ampacity within conduit for what you suggest. The local code to your area is designed around fire-safety, not max ampacity possible in the conductor.
 

MisterBill2

Joined Jan 23, 2018
9,792
The TS is not located here in the US, and so getting access to the electrical code for that area may be an issue, which is why we are getting all of these questions. And there are places where to pass the inspection one must pay the inspector extra. I discovered that when my one employer sold some equipment to a customer in another part of the world. It was rather unfortunate.
 
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