The Bonding Wire in BX/AC Cable

Old 12-04-12, 06:22 AM
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The Bonding Wire in BX/AC Cable

Does the Bonding Wire truely serve as the ground in a AC/MX cable.
Or is it that and a combination of the metal jacket in AC Cable/Bonding Wire and the connector on the panel - full steel box that makes the ground connection.

Traditionally, out here in BX Land NYC, I've never added a seperate ground.

I was just looking at my panel. I'm pretty positive my sparky ran flex and stranded wire *when he ran a feed for my minisplit system*. All I see are 3 wires *2 H and a N*, WITH a bonding wire holding the bushing and wrapped around the entrance of the flex where it meets the panel. I would think a large run like this (50 Amp circuit) - he would have ran 4 Wires .

I'm planning to add a transfer switch. I do plan to run 4 Wire from the switch to the Inlet. Am I only running 3 Wire from the Panel to the Switchbox.
Old 12-04-12, 08:26 AM
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Flexible metal conduit, sometimes caled Greenfield, is different than Type AC or MC cable. It does not have a bond wire and needs a separate grounding conductor.

Type AC cable uses the sheath and the bond conductor as a grounding means. Type MC cable has a grounding conductor in the sheath.

Your split system sounds like it is 240 volts only and would not need 4 conductors.

Your inlet will need to be wired with 4 conductors in order to bring in the 240 along with a neutral and a ground.

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