4 AWG and bigger

[Pinnie]

The Code starts making rules for wires 4 AWG and bigger. Like identification of grounded conductor, protective bushing in conduit, pull boxes with wire 4 AWG and bigger have to be sized differently.

Anyone know why that line in the sand was drawn? Is that something to do with manufacturing or ampacity of conductors or something else? Maybe available fault current at that wire gauge?

 

[TwoBlocked]

Good question. I've wondered the same thing. I don't argue with it, though, especially with box sizing.

 

[tom baker]

For reidentification of neutral and EGC, 4 and larger are sizes that will stay during life of building, so those can be reidentified

 

[Pinnie]

For reidentification of neutral and EGC, 4 and larger are sizes that will stay during life of building, so those can be reidentified

Ahhh that makes sense. Thank you Mr. Baker. Do you by chance know why they chose to start at 4 AWG?

 

[Carultch]

Ahhh that makes sense. Thank you Mr. Baker. Do you by chance know why they chose to start at 4 AWG?

I expect that there was a history of #6 being the largest size you'd expect to use for branch circuit loads, which are important to clearly tell apart in a panelboard, in case someone reconfigures their breakers. While the big service or feeder wires, would be the only wires of that size, that you could easily tell apart by the original length and history of bends that remain in the wire's "memory". In other words, it'd be very unlikely to reroute the neutral to the main breaker's terminal by accident, when it has a prevailing bend pattern that leads it directly to where it belongs.

#6 is what you'd have to use for a 50A stove circuit in the old days when 60C terminal limitations were the industry norm. Whereas #4 and larger would be what you'd expect to use for a feeder to a subpanel, or for the service conductors, that would remain permanently installed, with no expectation for a home-owner to change it in the future.

 

[Pinnie]

#6 is what you'd have to use for a 50A stove circuit in the old days when 60C terminal limitations were the industry norm. Whereas #4 and larger would be what you'd expect to use for a feeder to a subpanel, or for the service conductors, that would remain permanently installed, with no expectation for a home-owner to change it in the future.

That makes sense!

 

[LarryFine]

Do you by chance know why they chose to start at 4 AWG?

Until recent years, most wires were made in colors only up to to #6; larger were always black, so the code was designed around what was made, like code allowing white wire to be used as hot under certain circumstances.

HVAC control wiring similarly used the colors that were available; red and white for two-wire, green for the fan in 3-wire, yellow for cooling in 4-wire, etc.

 

[Birken Vogt]

Until recent years, most wires were made in colors only up to to #6; larger were always black

I can think of some installations with larger colored wires going back to the 60s, and maybe the 50s.

 

[kwired]

For reidentification of neutral and EGC, 4 and larger are sizes that will stay during life of building, so those can be reidentified

Sorry, I don't buy that as the reason. Lots of conductors of varying sizes tend to stay for the life of some buildings. Also many conductors of 4 AWG and larger do get taken out and maybe replaced with even larger conductors as load in a building grows over time.

I might buy the idea of what was commonly available at one time. Anymore you can sort of get almost any size conductor in any color, or at least commonly requested colors are more commonly stocked by suppliers, and suppliers even will make up reels for you with multiple conductors - multiple size and color cut to desired length and you just rack it up and start pulling. Years ago we always just got black for everything 4 AWG and larger and marked the ends in the field, often measuring multiple pieces off one common reel in field before pulling.

I can think of some installations with larger colored wires going back to the 60s, and maybe the 50s.

I have seen some of that as well. Not extremely common but there is some out there. I think it came down to either special orders or whether there was enough demand from a supply house to order more than just black, particularly in larger sizes.

Around here there is also a lot of 6 and 8 AWG with white or green tape that was installed in 70's and 80's. Pretty sure code required them to be green or white full length, I'd say it was done because of lack of enforcement and/or lack of availability from suppliers because of no demand for it. When enforcement started kicking in demand went up and those items were available.

 

[Birken Vogt]

How many AHJs enforce it anyway? Around here I don't think they do for anything bigger than #10

 

[Eddie702]

When I started in 73' most supply houses only stocked black in the larger sizes. I am sure colors could be had on special order but we only saw black in #8 and larger. #10 and smaller were available in colors.

As far as I am concerned you should be able to reidentify anything #8 and larger. In fact #14 and up would be ok with me. I don't see the issue. I suppose it's to protect the home owners.

Electricity is color blind and should be treated as such anyhow. I have nothing against colors it makes things easier but on a rewire re identification should be allowed.