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#101665 09/11/02 06:08 AM
Joined: Apr 2002
Posts: 15

I am looking for some advice from a Canadian electrical inspector.I have three parralel runs of cable with at least 100% distance between them,.These cables are run in a ventilated csble tray, and are used to form a single service. These cables will be exposed to an ambient temperature below 30 degrees celcius for 355 days of the year and a maximum of 10 day above 40 degrees celcius.
1. Do I have to derate using table 5-A if it is only a few days a year of 40 degree temperatures?
2. Do I have to derate using table 5-C. It says in section 12-2210-1(b)(In the 2002 CEC edition),that for multi conductor cables you use the number of conductors in each cable to determine the derating factor. If I have 3 parallel runs of tech cable to make a single service, and I do not count the neutral or ground conductor that leaves me with 9 conductors, 3 in each cable.If I counted all nine
I would have to derate my cable to 70%. This seems a bit extreme. I should be able to keep it at 100% ampacity due to only 3 conductors per cable.
Thanks for any help and code rules I can refer to

Greg Smith
Camp Black Bear

Joined: Jul 2002
Posts: 175
Derating for ambient temperature under Table 5A is a judgement call and will depend on your inspector. I would if it was me.

Assuming the cables are 4 conductor TECK and the load is balanced, you will not have to count the neutral for derating purposes, and will not have to derate under Table 5C.

If the cable spacing is more than 100% of the cable diameter derating under Table 5D is not required.


[This message has been edited by electric-ed (edited 09-11-2002).]

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