Why use 90degC cable with 75degC terminals?

1 reply [Last post]
bella1234's picture
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Joined: 2017-05-05

I understand how you have to use the ampacity rating of 75degC conductor when the equipment is rated for 75degC even if the conductor insulation is rated for 90degC.

I would think 90degC cable is more expensive compared to 75degC cable, so why wouldn't I use 75degC cable if the terminals are rated for 75degC? Is it advantageous from the derating standpoint? Because ampacity of a given cable would be after all the derating factors are applied.

Joebanana's picture
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Joined: 2017-04-18

The difference in price is negligible. You were close with the "derating" idea, but now it's called ''correction", and "adjustment". Otherwise, if it's under 100A you use the 60degC column, unless the terminals are rated at 75degC.

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