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Discussion Starter #1
Hi All,

I have a "220" 15a 14-3 circuit supplying an air handler. I am trying to complete a final inspection and one of the to-do's from prior trips by the inspector was to come off the switch box w/ AC cable due to it sitting well off the area of framing. Right now it is romex to the equipment shutoff switch in a plastic box, then more romex to the AHU.

My plan is to switch out the box w/ a metal box and then run AC w/ proper clamps etc to the AHU. My question is this... I understand that 220V circuits do not utilize a neutral wire. The only AC I have is 2 wire w/ that very suspect aluminum wire which if intended to be a ground can't be a great one. Since it's a grand total of about two feet, can I just pull a 14# wire and tape it green and nut it at the box and AHU, maybe with a pigtail to ground the box itself? I mean in classic BX/AC, the ground comes from the metal cable itself, but from what I hear that's poor practice if it can be avoided.

I guess the other side concern is potentially energizing the box by grounding it. Is it 100% correct that the ground on a 220 circuit will never be hot unless something goes wrong (like in any other grounded circuit)

Final side note - I understand current code is all boxes have neutrals. This circuit was in place beforehand and my HVAC guys are in the Hacktastic Hall of Fame. I may address it some day but for now I just want to pass inspection w/o running new cable and especially w/o blowing the place up.

Thx!
 

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Licensed electrician
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Type AC cable uses the spiral sheath and a thin bond wire as the ground. No need for anything to be taped to it.
 
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Not ALL boxes require a neutral. The new requirement is for neutrals at switch locations. 240 volt circuit does not require a neutral unles it is a 120/240 volt circuit.
 

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Usually Confused
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You say you have a 220v circuit using 14-3 cable. What is the third conductor for?
 

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I mean in classic BX/AC, the ground comes from the metal cable itself, but from what I hear that's poor practice if it can be avoided.
It's fine to use the AC armor as equipment ground. As Jim Port pointed out, that's why it's there! You might be thinking of flexible metal conduit for a poor ground. It's sometimes mistakenly called BX. FMC does have limits on its use as a grounding conductor because it lacks the bonding wire.

I guess the other side concern is potentially energizing the box by grounding it. Is it 100% correct that the ground on a 220 circuit will never be hot unless something goes wrong (like in any other grounded circuit)
It will never be hot unless something goes VERY wrong. The equipment grounding conductor, and thus the box itself, provides a current path back to system ground. When there is a fault (one of the hot wires somehow makes contact with the metal) this path creates a short circuit and trips the circuit breaker. Without the ground the fault won't create a short circuit and the box will stay at live potential.

Connect the ground from the Romex to the box with a grounding screw. The AC box connector will take care of the ground connection for the AC cable.

Final side note - I understand current code is all boxes have neutrals.
Only boxes with switches for lighting circuits. Even then there are many exceptions.
 

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Discussion Starter #7
Thanks guys. I now realize I made a few stupid typos in my original post (probably because it was like 2am when I wrote it :p). It is not a 14-3 circuit rather 14-2. There is no neutral wire at all. I also meant to say NEC calls for neutrals at all switches, not boxes... but either way I guess I have the answer that furnace cutoffs are not applicable. Bonus points for also confirming my last assumption which was to ground the romex to the metal box :)

Right after I posted I studied up on dual hot circuits and now recall what I had originally forgotten, which suddenly made them make much more sense - that neutrals usually only go to dryers/ovens/ranges et al to break out a 120v circuit for clocks, lights, etc.

Also learned that the "ground wire" in AC is wound around the inside to ensure contact is made w/ the outer sheath and doesn't necessarily need to be bonded (if that's the right term) to the box or device itself esp if you want to avoid a copper/aluminum connection. Somehow I had it in my head that grounding via the sheath was kind of old school and frowned upon, but maybe more modern AC solves that problem w/ the wire... my house actually has a bit of both old and new as well as Romex now. Good times :)

Thx again!
 
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