Motor Lead Connections

Status
Not open for further replies.
P

peterlevitt

New member
Location
New York City
When is it safe to use wire nuts for connecting incoming power to motor leads? At what amperage or conductor size, should un-insulated crimp on lugs & nut/bolts be used?
We have a customer who wired a 20 HP motor (230 volts, 46 FLA) to #6 or #4 lines with wire nuts. Our 60 amp AJT fuses blew immediately. We feel this was caused by the high resistance connections of the wire nuts & want them to be changed to lugs. We will also increase the fuses to 80 amps.
The electrican says the wire nuts comply with NEC. Help!
 
Re: Motor Lead Connections

Originally posted by peterlevitt:
When is it safe to use wire nuts for connecting incoming power to motor leads? At what amperage or conductor size, should un-insulated crimp on lugs & nut/bolts be used?
We have a customer who wired a 20 HP motor (230 volts, 46 FLA) to #6 or #4 lines with wire nuts. Our 60 amp AJT fuses blew immediately. We feel this was caused by the high resistance connections of the wire nuts & want them to be changed to lugs. We will also increase the fuses to 80 amps.
The electrican says the wire nuts comply with NEC. Help!
Click to expand...
high resistance would result in lower current not higher.

my guess is either:

th motor is wired wrong
or
fast blow fuses were used (although you stated they were AJT which are dual element),
or
the motor is bound up.

I don't like wire nuts at all having run across several of them that came loose due to vibrations, but I doubt they would cause a fuse to blow unless they did come loose and there was a short circuit inside the motor case.
 
Re: Motor Lead Connections

The wire nut splices were not likely the cause of your motor problems. IMO wire nuts are OK up to 10AWG conductors. Above that some type of mechanical connection, set screw connectors, bolted crimp on lugs or split bolts.
 
Status
Not open for further replies.
Top