High Temperature Lead Wire (Sizing Conductor)

tester730 · Oct 2, 2005

We have been using the Belden cable : 4/0 # 37140
EPDM - Ethylene Propylene Diene Monomer Rubber.
The temperature rating by specs are:
125?C (UL AWM Style 3340), 125?C (UL AWM Style 3374), 150?C .

I can't find any reference in the code to size this type of conductor.

Belden has a table that shows :

150?C
EPDM,
XL-Dur,
Silicone

---------------------------
4/0 332
---------------------------
Current carrying capacity of not more than three (3) conductors in a raceway, conduit or cable.
The values (amperes) shown in this table are maximum at an assumed ambient room temperature
of 30?C (86?F).

*************************************
I understand that below 100 A I can use the table 310.16 60C column and Higher the column of 75C.
If this cable is not shown in the code how should I undertstand the 331 Amps shown in the Belden's table ?

Is there any equivalent conductor that I can use as reference in the code (THHN,THW)?

Regards.

infinity · Oct 3, 2005

Re: High Temperature Lead Wire (Sizing Conductor)

I understand that below 100 A I can use the table 310.16 60C column and Higher the column of 75C.

The problem that you'll have using a 150 degree rated conductor is that the terminations will only be rated at 60 or 75 degrees. Therefore your cable ampacity will be limited by the sizes listed in table 310.16 in one of those columns. However your 150 degree conductor rating may be used for derating purposes if it's installed in an area of high ambient temperature.

charlie b · Oct 3, 2005

Re: High Temperature Lead Wire (Sizing Conductor)

I think this is a trickier problem than that. Let me see if I understand the question correctly.

The manufacturer says that the ampacity is 331 amps. (By the way, is there a typo here? Should it be 332?)

The manufacturer says that the cable's insulation system can withstand an operating temperature (ambient plus I*2 R heating) of 150C.

You suspect that if you were to install this cable in a 30C ambient, and pass 331 amps through it, the cable would reach that operating temperature of 150C. You know that this would risk damage to terminations that are only rated at 75C.

You do not know what current you can pass through this cable, given an ambient of 30C, and given the desire to limit the operating temperature to 60C (or to 75C).

This cable is not shown in the NEC Tables. You are looking for a comparable cable that is listed in the NEC, so that you can use the relevant NEC Table to get the ampacity at 60C (or at 75C).

Is that your question? If so, then the NEC will not give you an answer. You have to ask that question of the manufacturer.

High Temperature Lead Wire (Sizing Conductor)

tester730

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infinity

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charlie b

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