NEC 110.14 and highly stranded wire on oven

[tom baker]

That would be a listing and labeling issue...only permitted if the manufacturer has specified that method of termination for finely stranded conductors. At one time SquareD had an instruction that showed wrapping the finely stranded conductors in copper foil for terminating in set screw connectors. Not sure if they still say that.

I have seen copper foil on generator fine stranded terminations.

 

[tom baker]

Polaris makes connector listed for fine stranded wire

 

[wwhitney]

Polaris makes connector listed for fine stranded wire

Right, the grey top ones, see post #2. Anyone know how they differ inside from the normal black top ones?

Cheers, Wayne

 

[curt swartz]

Right, the grey top ones, see post #2. Anyone know how they differ inside from the normal black top ones?

Cheers, Wayne

Not sure what other internal differences there are but the conductors go into a tin plated copper ferrule so the set screw is not directly contacting the strands.

 

[tajalir]

Thank you very much. This is a lifesaver. I have been looking in vain for something like this. Google's AI did not come up with it.

One option: https://nsiindustries.com/product/2-port-grey-multi-tap-pre-insulated-connector-6-14-awg-bag/

Cheers, Wayne

 

[tajalir]

Are Wagos rated for finely stranded wire?

No. They are not. I checked with the manufacturer.

 

[tajalir]

Every oven for for residental use has flexible metal conduit with finely stranded wire? Since when? I have see a few with this but most are set up for cord and plug use. Can use a 3 wire cord for older 3 wire outlets or a 4 wire cord for newer outlets.

I should have said every double-oven. That is the unit I have. I have a range in the apartment and it has a cord and plug.

 

[tajalir]

Oven or range? Every range I've seen has terminals for a cord. Built in ovens tend to have a FMC whip which generally needs to get spliced to tapped in with the cooktop and branch circuit conductors. I haven't had a built in oven for over 30 years, and I don't think I ever took that one apart to know if it was fine strand or not. I assumed they would use AWM or MTW that is 105C.

It is typically AWM, 105C.

 

[tajalir]

What problem? Specs allow the use of solid or stranded wire with multiple combinations thereof. You have stranded wire, end of story. If you have a problem, you are probably not striping the conductors correctly or not letting the stranded lead the solid or not twisting the stranded. If after installing the wire nut you can tug either conductor and it doesn't come out, you have done it correctly.

-Hal

Not so. The way UL tests the connectors, they only use Class B and C strands. If the connector is to be used on other classes (high strand) the connector must be tested and listed that way. Typical connectors in the market are only rated for Class B and C. That is why NEC requries the connector to be "identified" for highly stranded wires if it is to be used that way.

 

[tajalir]

Chapter 9 Table 10 tells us that for #14 to #2, Class B stranding is 7 strands, and Class C stranding is 19 strands. So if the oven comes with an FMC whip with conductors with more than 17 strands (e.g. 37), then the connection in the outlet box requires a special connector per 110.14.

Cheers, Wayne

That is correct

 

[tajalir]

Now find me where the wire nut specs don't allow their use with that wire. It only says they may be used with solid and stranded with no distinction between any particular stranding. So, I take that as saying they are identified as being suitable for this use per 110.14.

In my opinion 110.14 pertains to setscrew, pressure terminals and crimp lugs.

-Hal

The wire nsut specs are confusing in many ways. NEC is very specific about highly stranded wire and the connector requirement.

 

[tajalir]

Are you hard wiring this residential oven?

Yes. That is how it comes - with high-strand wires in a flex conduit from the factory. One manufacturer (forgot which one) even said in its installation manual that you should not replace the whip (flex) with a cord and plug.

 

[tajalir]

That's not what 110.14 says. It says that for other than Class B and Class C, the connector "shall be identified for the specific conductor class or
classes." So if the whip conductors have class K stranding, then the wirenut packaging needs to say "suitable for class K stranding" or something like that.

Cheers, Wayne

That is correct. The connector must be "identified" as suitable for highly stranded wire.

 

[tajalir]

Look at the last part of the parent text of 110.14.

I am not aware of any wire nut that has been identified for use with finely stranded conductors.

That is the problem I had. But Wayne (above) solved it. NSI manufactures it. But it is pricey.

 

[tajalir]

I am just curious with regard to a "wirenut" and class K stranding...... Isnt SO cord or lamp cord ( from a pendant luminaire), also a type K stranding? If so dont we all use a "wirenut" to connect these conductors to building wiring?

Again just curious persuant to the current discussion.


Howard

I have been puzzled by the fact that this problem has not been getting more attention in the past. I believe that highly stranded wires are routinely connected to regular (Class B and C stranded) wires with wire nuts that are only "suitable" for Class B and C strands. Why does this not get attention from the AHJs? I reached out to two AHJ's (chief electricals), and they do not seem to be aware of it. So at first I thought I was losing my mind (which I have, according to the wife). But the more I look at this (and reading UL486, the standard for connectors), I am convinced that manufacturers of connectors only test with Class B and C strands. So the NEC article makes sense.