When wiring two circuits through the same conduit, what wire coloring is required?

Question

Problem

I am wiring a septic control/alarm box to a subpanel. They are on the same post, so the wire run is through a short stretch of 3/4" flex conduit.

There are two circuits required: a 240V for the pump and 120V for the control/alarm system. I'm using 12 AWG wire, as follows:

• hot to alarm
• neutral to alarm
• hot 1 to pump
• hot 2 to pump
• ground

What does code say about coloring and grouping of these wires? What about best practices, beyond code?

My Current approach

I'm currently using:

• a 12/2 G cable.
  • Black is alarm hot;
  • white is alarm neutral.
  • Bare is ground (duh).
• a black wire is pump hot 1
• a white wire with red tape at both ends is hot 2

That seems confusing, and I'm not sure if it's quite to code. How can I improve it?

Since it's a short run, I really don't mind buying new colored wire by the foot and redoing all of this.

An alternative

I have a bit of 12/3 G cable that I considered using like this:

• 12/3 G cable
  • black is pump hot 1
  • red is pump hot 2
  • bare is ground (duh)
  • white is neutral to alarm (remember, pump has no neutral)
• single black conductor to alarm

I rejected this because I didn't like the idea of the control box's neutral being in the cable with the pump's conductors - more confusion.

My neighbor's control/alarm box

For comparison, here's my neighbor's control alarm/box, although it uses a 120V pump, so the white wire really is a neutral. (Click for full-sized image).

Answer 1

As far as code goes, I think you're okay with your approaches since you've tagged hots appropriately.

Personally, I think mixing cable with individual wires is sloppy. I'm going to assume that 12 AWG is the correct size for the pump, but you should check before actually putting in 12 AWG. I would do one of two things:

Run using NM cable:

• A 12/2 wire for the 240V pump circuit: either black/red, or black/white tagged as hot
• A 14/2 wire for the 120V alarm circuit
• Ground in both cables is connected

Or run individual wires:

• 2 12AWG's (black/red) for the pump circuit
• 1 12AWG or 10AWG ground (bare, or green)
• 1 14AWG white neutral (alarm circuit)
• 1 14AWG other color (blue is often the 4th color used) hot for the alarm circuit

NM wire is usually easier to find, and you may even have some already (if not, having spare 14/2 available is never bad). For individual wires you often have to buy a spool of each color which makes going that way for one project more expensive, though you may be able to buy by-the-foot.

In either scenario, labelling everything at both ends is important.

Answer 2

Jay, either of your approaches would be fine. Putting red tape or "painting" a white conductor red is perfectly acceptable. To avoid any future confusion, you could also tag the conductors with labels or post a diagram of what you did inside the control box.

Answer 3

The obvious one is to use red for the second hot. However what do you di with your "third" hot? I think you could go with blue or orange (I think this is usually for another phase). In your case you would just be taping the wires to these colors.

I am not an electriction nor can I cite a section of the NEC that would apply to this.

Answer 4

From your description, I'd suggest the following:

• x/3 G from the main to the subpanel, where x is the appropriate size for your distance.
• x/3 G from a 240v breaker to the pump. Cap the neutral if the pump doesn't have a place for it, but still run the wire to avoid future confusion. Since it's a short run, the reduced confusion will more than offset any costs.
• x/2 G from a 120v breaker to the control panel.