Connections and Termination Standards

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pault587

Member
Location
Grand Rapids, MI
I put this in safety because we nearly had a fire. A resistive heater in an oven had a wire nut in its junction box that seemed to installed improperly... This is a manufacturing enviroment.

I am looking for anyone willing to share their standards or a small part of a standard that talks about acceptable connections. If you can not share this can you share you opinions?

I would like to cover motors, heaters, other types of terminations and connections. Do you ever accept the twist on wire nuts?

Please get as specific as possible for me, I am truly searching for knowledge here. Thank you.
 
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bphgravity

Senior Member
Location
Florida
I suggest you contact the manufacturer of the appliance and/or the NRTL that has listed the appliance. One or both will be able to discuss with you applicable standards and proper wiring terminations.
 
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bphgravity

Senior Member
Location
Florida
I have sen wirenuts and other removable type connectors used on manufactured wiring components where it is necessary to remove parts for replacement or re-wire for different voltage connections, etc...
 
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klillemo

Member
Location
Twin Cities, MN
Crimp Connectors

Crimp Connectors

Crimp connectors for heaters in carnival style popcorn poppers are made from stainless steel. Typical plated copper connectors oxidize rapidly from the heat creating a high resistance connection. The power dispated in this resistance heats up the connection further leading to more resistance, higher power dissipation snowballing to rapid failure.

Stainless steel, even with it's inherent lower conduction than copper is a much more reliable crimp connector for heater circuits in close proximity to the heat source.
 
pfalcon

pfalcon

Senior Member
Location
Indiana
Wire nuts at our site are not specifically banned. We push for Jboxes with terminal blocks or the use of quick disconnect cables. We would question any machine purchased that used wirenuts anywhere.
 
PetrosA

PetrosA

Senior Member
Location
Lancaster, Pennsylvania
I can only approach this from a material POV. If the wirenut shell was rated for the expected temperatures in the JB and what heat may have been transferred through the wire, I'd say it's within what UL ratings would allow. Regular Ideal type wirenuts are rated for 105?C. Their High Temp wirenuts extend that to 150?C. Porcelain wirenuts can be rated as high as 550?C. This may sound old fashioned or naive, but if the environment is that harsh, wouldn't soldering first be the best idea?
 
brian john

brian john

Senior Member
Location
Leesburg, VA
PetrosA said:
I can only approach this from a material POV. If the wirenut shell was rated for the expected temperatures in the JB and what heat may have been transferred through the wire, I'd say it's within what UL ratings would allow. Regular Ideal type wirenuts are rated for 105?C. Their High Temp wirenuts extend that to 150?C. Porcelain wirenuts can be rated as high as 550?C. This may sound old fashioned or naive, but if the environment is that harsh, wouldn't soldering first be the best idea?
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Interesting and helpful.

Thanks for that
 
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billk554

Member
if you look on the box the wire nuts came in there is manufacturer's directions for use. ya cant go wrong there. if people refuse to use them thats their problem. i find them time saving whe replacing certain things and if butt splices are used well you can only use them so long or untill the wires get too short ot use then your pulling new wire. but its up to the plant and their own set of standards
 
Ranch

Ranch

Senior Member
Location
Global
pault587 said:
A resistive heater in an oven had a wire nut (yikes - no inductance, no buffer) . . . Do you ever accept the twist on wire nuts?

Categorically NO – didn’t a recent thread discuss cage clamp? I suppose the Meret company doesn't want to hear my opinion . . .
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TxEngr

Senior Member
Location
North Florida
Wire nuts are prohibited in the manufacturing areas. If a connection must be made that is removable, round lugs with bolts are used and properly taped to prevent moisture intrusion. The office environment in the plant is another situation.

I've only seen wire nuts used once in 20 years in the manufacturing area, and it was an emergency situation where we had run out of crimps in the middle of the night after a fire damaged a control cable tray. We're removing that cable this week and replacing with dedicated runs and no splices because of our concerns about the wire nuts.

TxEngr
 
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big john

Senior Member
Location
Portland, ME
This is new to me, I've never before heard of an entire section of industry that prohibits wirenuts. To be honest, I don't entirely understand the logic. I work in industrial settings and have found that if the environment is capable of destroying a wirenut, it is just as capable of destroying an exposed crimped or screw connection.

I'm not sure that one "style" of connection is inherently better than any other.

-John
 
highendtron

highendtron

Senior Member
I agree John, I have done a lot of industrial work...I use crimp ring terminals with nuts and bolts on motors or anything that vibrates a lot...I use wire nuts on fixtures in non corrosive environments...scotch locks for small power terminations, I don't think there are any accepted National standards and it is more a local or specific use preference. Naturally, if there are corrosive conditions or high temperatures, extra measures, ie, cloth tape, high temp connnectors, should be used.
 
quogueelectric

quogueelectric

Senior Member
Location
new york
highendtron said:
I agree John, I have done a lot of industrial work...I use crimp ring terminals with nuts and bolts on motors or anything that vibrates a lot...I use wire nuts on fixtures in non corrosive environments...scotch locks for small power terminations, I don't think there are any accepted National standards and it is more a local or specific use preference. Naturally, if there are corrosive conditions or high temperatures, extra measures, ie, cloth tape, high temp connnectors, should be used.
Click to expand...

When I have worked in powerplants the spec on marshalling cabinets for control were Phoenix connectors. I think they are the best termination available for wire compression terminals. They are expensive and eat up manpower yet are the best bang for the buck in my opinion.
 
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crossman gary

Senior Member
A pertinent question, as discussed, is "were the wirenuts used in compliance with the listing and instructions?"

I don't see any issue at all for using wirenuts if they are properly installed and used within their ratings.

Back when I was young and dumb, I went on a service call to connect a tar pot heater used in a manufacturing process. I pulled out my trusty crimp tool and box of ring terminals. The wiring in the heater j-box was not normal insulation, it was that glass thread type stuff, and the stranded wire was a shiny silver color, not copper, not aluminum. Hmmm....

Anyway, I made the connections to the studs/nuts in the connection box according to the wiring diagrams, using my "standard" crimp lugs. Turned her on, and let'er rip. Awesome. Working great.

About a week later, got sent back out there because the tar pot was not working properly.

Pulled the cover off, and the crimp lugs were all black and gunky looking, like when you heat copper up real hot and it oxidizes and corrodes and such.

Called my boss and told him what I saw. "Er... let me order you some crimp terminals that are manufactured for high temp locations." Went and got them, came back, redid the work, and as far as I know, she been heating ever since.

Moral: Spec that the connection devices have to be approved for the environment and installed according to instructions/listing.
 
weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
pault587 said:
I put this in safety because we nearly had a fire. A resistive heater in an oven had a wire nut in its junction box that seemed to installed improperly... This is a manufacturing enviroment.

I am looking for anyone willing to share their standards or a small part of a standard that talks about acceptable connections. If you can not share this can you share you opinions?

I would like to cover motors, heaters, other types of terminations and connections. Do you ever accept the twist on wire nuts?

Please get as specific as possible for me, I am truly searching for knowledge here. Thank you.
Click to expand...

A resistive heater should come with instructions on what type of wire is acceptable for connection. A well constructed heater should have a 'cold' lead connecting the heater element to the user's connection point where 90C* rated wire withe thermosetting or thermoplastic insulation may be used. Some heaters would specify a higher temperature rating requiring glass fiber insulation and nickel plated copper wire for connection.

In general all equipment connections specify the requirements.

What type connectors are required? Designed and approved for the purpose is the basic rule.

Some companies(users) will put restrictions on what type of connections are allowed for what application. Lighting and receptacle branch circuits are usually allowed to have wirenuts. Even 480 or 277V lighting. Compression connectors are preferred for everything else. Wago-type single action connections are gaining acceptance for low power - instrument and signal - type applications. Straight-through compression splices are always required to restore the insulation and environmental condition of the wire/cable.
 
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