Wire nuts

[Emach 0]

Hi all, Building a machine with a few fans, heaters and motors. When it came time to terminate the heaters, the plant EE said to crimp on a wire ring to each wire end, drop a bolt through and then retain it with a nut. My question is with 480VAC and maybe 10 Amps is it safe to use nylon lock nuts in an environment where it can reach +250 deg F? I don't know the formulation of the nylon used in the lock nuts, they are just bulk cheapo's off of Grainger, but we should stay below the melting point of Nylon 6,6 as its minimum is 375 deg F. (ATF the fuild being heated doesn't like to go much above 300 deg F before it starts atomizing and then you have the conditions for a nice dust explosion on your hands). Thanks in advance, Emach Edited 10 May 2012 by Emach

[Ken Roach 194]

I would definitely use the ring/bolt method. I wrap them in self-fusing silicone tape like Scotch 70, which is rated to be primary electrical insulation up to 356 F. Wire nuts are typically made of thermoplastic polypropelene, which gets soft as it heats up. I went out into the shop just now and checked a box of Ideal Wing-Nut (pretty standard industrial ones) and the maximum temperature they are rated for is 221 F. I'd also be more confident in a bolt/nut because I can generate a lot more torque on the bot/nut threads than on the friction threads of the wire nut, and that's going to resist loosening from thermal cycling better. I am not a licensed electrician or a EE; you'll probably find some of those weighing in on the topic, too. Another good place for questions like this is over on the MikeHolt.com forums. Those guys can quote chapter and verse from the NEC.

[BobLfoot 301]

Just my two cents. but AB, Pheonix Contact and others make sime nice multi pin voltage and current rated connectors when used per manufacturers specs. If you can find one suitable to your applicaiton and get the plant EE to buy off it will save them time when a heater , fan or blower finally does fail. They can have spare units wired with the machine side prewired and get the unit up much faster. We've found an AB conenctor for Motor Power that works great also.