conductor sizeing

[snogun]

I am installing a v.f.d drive.The drive termnals are rated at 75 deg C the wire I am useing is THHN rated at 90 deg. C for the incomeing power feed.Do I have to derate the ampacitie of the THHN because the drive termnals are rated at 75 deg.C

 

[roger]

Re: conductor sizeing

You must use the 75 deg ampacity. Read 110.14

Roger

 

[infinity]

Re: conductor sizeing

Roger is correct you must use the 75 or 60 degree rating depending on the rating of the lugs that the feeder is connected to. The 90 degree rating can be used for derating purposes. I would also add that the feeder ampacity to the VFD must be sized for the VFD and not the motor.