What wiring codes say about these wires?

[mm]

I think the blue wire is for patriotism.

[RBM]

There is a particular type of three phase service called a "Delta", where two of the three legs will give you 120 volt to neutral, but the third leg, called the wild leg, high leg, delta leg, or red leg, gives a much higher voltage to neutral and is not used in single phase applications

[Stormin Mormon]

It's an interesting project. I'd be thinking to trace the wires back, and see where they go. That will help give you information on how to wire the outlet end.

It sounds, though, that you should hire an electrician.

[Rick]

May be 480 Wye using 277 volt fluorescent fixtures...

[RBM]

The OP doesn't really make it clear if this is a house, apt, or commercial building, so anything is possible

[Terry]

Actually, single phase applications are the only reason a high leg exists.

If it were all 3 phase loads there would be no high leg.

I know it is more than the OP wants to know, but

[Terry]

I should have said that the 190V leg is not used in the single phase applications, but the need for single phase applications is the only reason the high leg is a factor.

That sounds a little more like I know what I am talking about, but not much. :)

[jJim McLaughlin]

Odd photos.

All appear to come into the box in an armored cable. Looks sort of BX ish, but the BX I know is black, white and bare copper ground, if there is a ground. Old code sometimes allowed BX armored sheath as a ground. It wasnt a good ground as the amored sheah could corrode, break, and then no ground.

In photos of the box are insilated wires in black, red, blue, white with a red tracer thread, and a bare copper.

The bare copper is grounded to the box with a screw.

In US household wiring, conventional wisdom would suspect black and red being separate 120 hot legs; blue is also used in conduit as a third color for a hot leg. Its also used *inside* a fluorescent fixture or one of the high frequency legs.

A plain white *should be* a neutral. What a white with a red tracer thread is I have no idea.

I wouldn't touch this with a 10 foot pole.

[Meat Plow]

Call an electrician before you kill yourself.

[Bob M.]

Probably none. Household AC does not have shielded wire. Get a pro to do this, it sounds like you don't know how to do it.

[Mark Lloyd]

When I put up ceiling fans, I found they had blue wires. There were hot wires for the light kit, allowing wiring to separate switches.

[Mark Lloyd]

I thought they did something like that when they used the same cable for 2 circuits with their own neutral wires. That would be needed if they used GFCI breakers.

[Terry]

The only reason to mark the white would be if it had two whites.

It could be, like you say, two single phase circuits.

It looks like 3 phase to me, but who knows without checking?

There are no missing knockouts in the box. It looks like a circuit that has never been used. It could be that or they removed something and put a box on the end.

[Tom Horne, Electrician]

There are several reasons to mark a white wire in a building wiring system. One of those reasons is that the building has two or more different voltage systems. Since you've already said that this cable comes from a lighting panel there is a definite possibility that the cable carries 480/277 volt power.

[gfretwell]

Typically red/black/blue/white is used for 3 phase wye 208v

3 Phase center tapped delta 240v requires that the "high leg" be orange and they usually would not bring the neutral into a box with the high leg present. 480v 3p wye is usually going to be using brown orange and yellow and when they do split off a 277v L/N circuit they will use violet (hot)and grey(neutral). That is the normal convention but the only things specified in the NEC is the white or grey for neutral, green, green/yellow stripe or bare for ground and orange for the high leg of a center tapped delta. Any other color is legal for a hot. You can see why they came up with the convention and any real electrician will follow it. Anything else signs your work "hack"

[mm]

That means when the OP hooks up the vacuum, it will really suck.

[Terry]

That is funny. :)

[Doug Miller]

Briefly.

[jJim McLaughlin]

Looking closer at those photos, the white has both red and blue tracer threads on the insulation jacket. Very wierd.

[Joseph]