Temp limitation of conductors

[deetz]

Looking at NEC code 110.14 (C) I am wondering if we were to install copper lugs (rated for 90deg.) on a machine disconnect that is rated for 75deg., would I then be able to use 90deg. rated conductors? I know it comes down to how the Inspector interprets it in the end. I just am trying to cut costs wherever I can.

 

[dpc]

The UL listing of the disconnect is based on the 75 deg C lugs. If you change out the lugs, you probably no longer have UL listed device. Also, you have to consider the terminations on the other end. Almost nothing in the low voltage realm is rated for use at 90 deg C ampacity - at least in the US.

 

[deetz]

Thanks for the reply. I am not really replacing the connections to the switch. The clamp type connectors on most of the machines we get are not that good of a connection, and crimping on a ring terminal is another not so good of a connection, so we just use a type ML barrel post lug. It actually is used on both ends because the other end goes to a transformer. But, yeah I get where your coming from on the UL side of things.

 

[dpc]

I wouldn't go there. Scrimping on conductor size should probably be way down on your cost-saving list.