I have recently read in the 2002 version of NFPA 79 that twist-on connectors or wire nuts cannot be used to terminate conductors in motor terminal boxes. It is section 14.5.9.2 in 2002 edition and is also in the new version of NFPA 79. Is there any reference to this same rule in the NEC??
NFPA 79 vs. NEC
- Thread starter wattup
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charlie
Senior Member
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- Indianapolis
From NFPA 79, 2007 Edition:
13.5.9 Motor Connection Boxes
13.5.9.1 Motor connection boxes shall enclose only connections to the motor and motor mounted devices (e.g. brakes, temperature sensors, plugging switches, tachometer generators)
13.5.9.2 Electrical connections at motor terminal boxes shall be made with an identified method of connection. Twist-on wire connectors shall not be used for this purpose.
13.5.9.3 Connectors shall be insulated with a material that will not support combustion.
13.5.9.4 Soldered or insulation-piercing-type connectors (lugs) shall not be used.
It is my opinion that the motor vibration could loosen the connections of twist-on wire terminals. It would seem to me to be a good proposal for the 2014 Edition of the NEC.
13.5.9 Motor Connection Boxes
13.5.9.1 Motor connection boxes shall enclose only connections to the motor and motor mounted devices (e.g. brakes, temperature sensors, plugging switches, tachometer generators)
13.5.9.2 Electrical connections at motor terminal boxes shall be made with an identified method of connection. Twist-on wire connectors shall not be used for this purpose.
13.5.9.3 Connectors shall be insulated with a material that will not support combustion.
13.5.9.4 Soldered or insulation-piercing-type connectors (lugs) shall not be used.
It is my opinion that the motor vibration could loosen the connections of twist-on wire terminals. It would seem to me to be a good proposal for the 2014 Edition of the NEC.
Thanks Charlie. I had noticed many had viewed my question but none had answered until you did. I assume that nothing in NEC prohibits use of twist-on terminals at this time. We have always used them on smaller fractional HP motors and changed to split bolts and other means above that. Your guess is what I had thought that since NFPA 79 is standard for Industrial machinery they are concerned about vibration issues. Thanks again for your reply.
charlie
Senior Member
- Location
- Indianapolis
I believe your assumption is correct. :smile:
chris kennedy
Senior Member
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- Miami Fla.
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- 60 yr old tool twisting electrician
Who has the list of 'identified methods of connection'?
charlie
Senior Member
- Location
- Indianapolis
Identified (as applied to equipment). Recognizable as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular Code requirement.
FPN: Some examples of ways to determine suitability of equipment for a specific purpose, environment, or application include investigations by a qualified testing laboratory (listing and labeling), an inspection agency, or other organizations concerned with product evaluation.
Assuming the AHJ will assess the suitability of the connection AND the definition in NFPA 79 is essentially the same as in the NEC, they will look at the use and listing of the product. They will then identify it as being suitable for the purpose . . . or not.
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