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#220360 10/31/19 08:07 PM
Joined: Oct 2019
Posts: 1
C
New Member

Hey,

I'm working on a project and normally I run 2 parallel for a large distribution wire size. therefore I would typically divide my ampacity by 2. I've never really known where to find the divisor in the canadian code book. I was wondering if anyone knew where to find more clarity on this topic.

Joined: May 2015
Posts: 78
L
Member
Do you mean running a parallel pair to increase ampacity compared to a single wire (although dividing by 2 would put you back where you started wink )? If the two are close together, then they may have to be derated somewhat to maintain a safe temperature.
Since power dissipation in a given resistance is proportional to current squared, current only needs to be divided by the square root of 2 to halve the dissipation. In reality, you won't even have to derate that far as the two wires have a greater surface area than one of the same size; treating the pair as equivalent to a single wire of double the cross-sectional area (or with an AWG number 3 lower) should be quite safe (a bit more current may be OK as the two smaller wires still have more total surface than the bigger one, but I can't give precise or official data).

If it's just to reduce voltage drop, then you won't need to derate further.

This is just my understanding of the general principles; I'm not involved in distribution specifically, so there may be some detail I don't know about.

Last edited by LongRunner; 11/04/19 03:32 AM.

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