Accepted means of electrical motor winding termination

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Electric_Santi

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Colorado
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Industrial Electrician
All,

There have been multiple discussions in our field recently about whether or not crimp lugs w/ a bolt-through style connection are accepted as a means of termination style for electrical motor windings. It is to my understanding that the NEC does not specify for or against the style anywhere. Coming up in the industrial field I was always told the style of termination is mostly accepted based on how it comes from the factory or however the specific motor manufacturer may outline in a manual. It is to my belief that all though the bolt-through style isn't the best means of connection, it is still accepted...help me prove my theory? Thanks in advance!
 
petersonra said:
Note use of phrase "I think". I don't think you will find any definitive answers to your question if you want some code or standard that forces a particular method.
Click to expand...
I have been lucky enough to find a few supporting documents from specific manufacturers and one from a motor tech support specialist...just curious what else might be out there. Thanks for the input
 
Electric_Santi said:
All,

There have been multiple discussions in our field recently about whether or not crimp lugs w/ a bolt-through style connection are accepted as a means of termination style for electrical motor windings. It is to my understanding that the NEC does not specify for or against the style anywhere. Coming up in the industrial field I was always told the style of termination is mostly accepted based on how it comes from the factory or however the specific motor manufacturer may outline in a manual. It is to my belief that all though the bolt-through style isn't the best means of connection, it is still accepted...help me prove my theory? Thanks in advance!
Click to expand...
It is my opinion that the crimp on ring terminals and bolts is by far the best connection for motors.

I have never seen instructions for any motor that detailed how the motor to supply conductor connection should be made.
 
Using bolted together crimp-on lugs or ring terminals was the only way we made motor connections when I was an industrial electrician during summers while in college. Lock washers are not required because of the "crush' in the copper or aluminum. This is analogous to the use of copper and aluminum crush washers for sealing high pressure hydraulic fittings.
 
I used one hole compression lugs for fine stranded wire, nut, bolt, washer, and lockwasher, with a bit of penatrox E.
For insulation I used a T&B motor stub boot
 
I have never seen a published standard, probably because there are too many variables involved.

The thing I HAVE seen, which addresses a number of arguments I have seen here and elsewhere, is that NFPA 79 13.5.9.2 prohibits the uses of “wire nuts” in making up motor connections. Mind you, NFPA 79 applies to INDUSTRIAL machinery, not residential, so don’t get excited or worried about all of the wire nut connections you may have made in homes. But when I started out in this industry at a steel mill, you could be fired for using white nuts on a motor connection. Since then, I have seen several failed motor terminations on industrial machines, some ending up catastrophic, all but one involved wire nuts. The other was likely just sloppiness.

The only other issue might be NEC 110.3 calling for following any manufacturers instructions in their listing. So if it is a new motor and you have access to their installation instructions, and those instructions list a termination method, you must follow that.
 
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