NFPA79 & Wirenuts 1

[kedminster]

I was reviewing a piece of industrial machinery for a client and discovered the machine builder used wirenuts to connect conductors in several places in the internal wiring of the machine. Included was several places where the protective (earth) ground was spliced/pigtailed using wirenuts. I really don't think this is an appropriate place to use wirenuts but can't seem to find a specific prohibition for their use in NFPA79. The wirenuts they have used are adequately sized and listed if this application was governed by NEC (NFPA 70). Is anyone aware of a design standard that prohibits the use of wirenuts in the internal wiring of industrial machinery? I always use DIN terminal blocks or other appropriate connectors in our designs.

Thanks in advance for any feedback

Karl Edminster

http://www.electromechanica.com

Does that smell like burning FR-4? Nah...just the FETs breaking in...

 

[itsmoked]

I do not know of any general prohibition, but man that is tacky! I'd complain.

As for the ground.. That seems wrong as normally you are supposed to have everything come to a single solid mechanical grounding point. Having a bunch of grounds meeting at a wire nut doesn't fit that. But where in the code?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[kedminster]

Keith,

I agree that wirenuts seem like a hack but I want to have solid ammo based on something like NFPA79 before I address this with my client. This is the kind of grey area where the judgment of the Authority Having Jurisdiction (AHJ) could cause problems when these units get out in the field. I know I don't want my name attached to a rats nest of cables & wirenuts.

Thanks as always for taking the time to review and respond to my question. It is appreciated!

Karl

Karl Edminster

http://www.electromechanica.com

Does that smell like burning FR-4? Nah...just the FETs breaking in...

 

[zappedagain]

There is an on-line version of NFPA 79 that you can view for free after registering:

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=79

I wish the rest of the standards would implement this so you can see if you really need them before you buy them!

John D

 

[kedminster]

John,

Thanks for posting that link. I already have a hardcopy of NFPA79 with very dog-eared pages. I have read through the wiring practices section (Ch. 13) but don't see anything about wirenuts.

Thanks again for your reply!

Karl

Karl Edminster

http://www.electromechanica.com

Does that smell like burning FR-4? Nah...just the FETs breaking in...

 

[amptramp]

I don't think you will find any "Code" prohibition, at least not in the US. I have hoped for years some authority would ban wirenuts from industrial service.

IMO, wirenuts have no place on a machine being placed in an industrial environment. I have argued this point many times over the years. The only recourse I have ever found successful was outlawing wirenuts in the engineering specification for the machine. This way the prohibition was an engineering decision.

 

[kedminster]

As a follow-up I wanted to let everyone know that the only prohibition I found to wirenuts was in NFPA79 (2007) 13.5.9.2 which states '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'. Although this prohibition is specific to motor lead connections (which is not my application) I still think wirenuts in a piece of commercial/industrial equipment is 'dirty' and I have strongly advised my client to require DIN blocks or other standard industry interconnect method.

Thanks again for everyone who posted!

Karl Edminster

http://www.electromechanica.com

Does that smell like burning FR-4? Nah...just the FETs breaking in...