2

The goal is identify hot and neutral wires in a 3-way switched line-array of lights, so that the array can be controlled by an Acuity SP20 Secondary Relay Pack (bottom device):

enter image description here

Said line-array of lights is the only 3-way switched several line-arrays. The other line arrays are controlled by a single switch. Said switches form a bank of switches at the building entrance.

The target line-array is located between the two switches:

enter image description here

Is there any reason to doubt that the wiring diagram above represents how the switches are wired? or maybe the better question is: How can I confirm that the that the diagram represents said line-array and that the hot and neutral are located at the switch bank located at the building entrance? Diagnostic procedures that are simple / less invasive are preferable

The sub-goal is: How to identify which common terminal of the 3-way switch is connected the hot wire (left 3-way switch) vs, the switched hot wire (right 3-way switch)

  • Clear pictures of the actual boxes would help this question. – Ecnerwal Sep 23 at 12:09
  • Is there any reason to doubt that the wiring diagram above represents how the switches are wired? ... yes, the diagram shows how the switches could be wired – jsotola Sep 24 at 3:06
4

Turn off breaker. Disconnect wires. Connect appropriate meter (safely). Turn on breaker, look at meter. If no voltage, turn off breaker, move to other switch, connect meter, repeat.

Or use a test lamp, if you are old-fangled. The folks around here are fond of "non-contact voltage testers" but they appear to be prone to confusing results. I'm old-fangled enough to prefer a meter, but not old-fangled enough to prefer a test lamp.

If your switches were actually wired "that way" you'd have a neutral connection in one box, and none in the other box. But things are often less clear-cut than that in practice - can't hurt to look for it, though.

| improve this answer | |
  • 1
    "old-fangled". I like that mashup of "old-fashioned" and "new-fangled". I think I'll borrow that one! – FreeMan Sep 23 at 12:11
  • 2
    This old-fangled guy wouldn't be caught dead with a wonder stick (non contact VT). Give me a meter every time.+1 – JACK Sep 23 at 12:24
  • Yikes! My preference for a meter puts me in the old-fangled category :) – gatorback Sep 23 at 12:30
3

I can't make sense of any of that German spaghetti. Here's how 3-way circuits are actually wired:

enter image description here

or

enter image description here

As well as 3-4 other possible rearrangings-of-furniture, giving the same wires doing the same loop, but on different routings.

Is there any reason to doubt that the wiring diagram above represents how the switches are wired?

Yeah, lots of reasons to doubt. 3-ways are always the same loop electrically... but topologically, there are at least 5 different arrangements by which the wires could be routed.

That is why I favor a functional approach of positively identifying the always-hot, switched-hot, and traveler wires, and marking them as such e.g. with colored tape.

The sub-goal is: How to identify which common terminal of the 3-way switch is connected the hot wire (left 3-way switch) vs, the switched hot wire (right 3-way switch)

  1. 3-way circuit must be working. 2) Measure it. 3) throw a switch. 4) Does it change?

As usual with smart devices, here is the takeaway:

Smart switches usually need always-hot (black in my diagrams), neutral (white) and often switched-hot (red). As you can see, this may not exist at some or any switch location.

As such, your choice of potential place to put a smart device may be limited, or nonexistent, without a complete reinvention of the circuit using smart tech.

| improve this answer | |
  • Interesting diagrams! The wiring inside the light fixture is red and white: reasonable to hypothesize and verify that the red wiring in fixture is switched hot and white is neutral? How to physically verify? – gatorback Sep 25 at 1:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.