480v - 10hp - MOTOR WIRING METHODS

[spark2]

I have come across several electric motors 10hp and above that have been spliced using wire nuts. I don't believe this should be an approved wiring method for motor terminations for motors 10hp & above. Is there any justification in the nec to support this?

 

[ceb58]

I have come across several electric motors 10hp and above that have been spliced using wire nuts. I don't believe this should be an approved wiring method for motor terminations for motors 10hp & above. Is there any justification in the nec to support this?

I dont think you will find any support in the NEC. As long as the wire nuts are listed for the wire size, # of wires and voltage there should not be a problem. What size wire are you looking at?

 

[spark2]

The wire size is #8 - thhn - wirenuts are correctly sized but we have come across melted wire nuts that went to ground taking motors out.

 

[realolman]

I don't see anything inherenly wrong with using properly sized, properly installed wirenuts on motor connections. I think ring terminals, screws, and nuts are a royal PITA.

I hope I can mention this without starting a big Brouhaha, but I think if you strip the wires long, twist them together and then cut them to proper length before installing the wirenut, your failure rate will be about zero.

I think if you have any concern about vibration, wrap the wirenut with the same stuff, you'd have put on the ring terminals and screws.




And as usual.....

 

[mcclary's electrical]

I don't see anything inherenly wrong with using properly sized, properly installed wirenuts on motor connections. I think ring terminals, screws, and nuts are a royal PITA.

I hope I can mention this without starting a big Brouhaha, but I think if you strip the wires long, twist them together and then cut them to proper length before installing the wirenut, your failure rate will be about zero.

I think if you have any concern about vibration, wrap the wirenut with the same stuff, you'd have put on the ring terminals and screws.




And as usual.....

I believe you're right. A properly installed wirenut should not fail or loosen just because it's on a motor. However, when wiring motors, I always tape wirenuts really well. It's THE ONLY time I use tape on a wirenut, but due to vibration, I think it's necassary. In the op's case, I'd be williing to bet the nuts became loose, then melted. They are capable of delivering reliable power when properly installed.

 

[don_resqcapt19]

While there is no code reason not to use wire nuts, it is not something I would ever do on a motor of that size. Its ring terminals and bolts for me, with rubber and plastic tape for the smaller motors and Raychems GelCaps for the bigger motors.

 

[DARUSA]

I have come across several electric motors 10hp and above that have been spliced using wire nuts. I don't believe this should be an approved wiring method for motor terminations for motors 10hp & above. Is there any justification in the nec to support this?

Some motor had aluminum wire You should be check if the wire nuts is rated for that application !!!!
Cooper aluminum splice!!!!

 

[btharmy]

Some motor had aluminum wire You should be check if the wire nuts is rated for that application !!!!
Cooper aluminum splice!!!!

Seen tin-coated copper (fine strands) but not aluminum that I can recall.

 

[sparky105]

most motors we wire are for someones business to run and to hinge a bet that a wire nut will do the job is not doing the best work we can do if the nut comes off and shorts or burns you cost that owner money more than it is worth to ring bolt and rubber in the first place quick is not the best way

 

[One-eyed Jack]

I have come across several electric motors 10hp and above that have been spliced using wire nuts. I don't believe this should be an approved wiring method for motor terminations for motors 10hp & above. Is there any justification in the nec to support this?

I have not had problems with the hp/voltage that you stated until the current goes above 30 amperes . Once you go over 30 I would go the nut bolt route.

 

[petersonra]

I have seen a fair number of wire nuts come loose under vibration. Maybe they were installed improperly, maybe not. I would not be seriously offended by the use of wire nuts to connect up small motors like this if precautions were taken to reduce the chances of the wire nuts coming off, such as taping them as another poster suggested.

 

[ray cyr]

The wire size is #8 - thhn - wirenuts are correctly sized but we have come across melted wire nuts that went to ground taking motors out.

Just curious, why such large wire? It seems that larger wires are not held as well with wire nuts as smaller wires, and # 12 would be fine for that amperage of motor.

 

[Cow]

Why do you have #8's running to a motor that could run on #14's?

Regardless, I don't go by HP, I go by wire size. So I'll use wirenuts up to #10's, sometimes #8's in a pinch, then wrapped in tape. But I prefer insulated taps for #8's and above.

 

[mcclary's electrical]

I have not had problems with the hp/voltage that you stated until the current goes above 30 amperes . Once you go over 30 I would go the nut bolt route.

That's a good rule of thumb, Most 10 hp 480 volt motors are fed with #10. IMO it's just not worth breaking out ring terminals, nuts, bolts, rubbertape, black tape. I've wired high speed production equipment that not only had rotational force of a sawblade on the motor, but was being raised up and down quickly by an air cylinder. They have been in production for 15 years without normal wear and tera problems. A # 10 with a wirenut and wrapped up good in black tape will certainly suffice.

 

[tom baker]

I agree with Don, I use crimp on lugs (copper only 8 AWG and larger) SS hardware, and T&B Motor Stub Boots.