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Followup to my earlier question about replacing a sub-panel and adding an A/C disconnect: I'm just taking a good look at the disconnect and I see that it has the two line voltage legs, OK, and another pair of lugs, electrically continuous with the case, which are labeled "Bonded Neutral".

My understanding is that it is a Bad Idea for neutrals to be bonded to ground anywhere outside of the service entrance panel, which is one reason why I'm replacing that 1960s-vintage panel. The A/C itself doesn't require a neutral; it's just 2 lines + ground. I was also planning on installing a convenience outlet attached to the disconnect in a weatherproof box and using the 3/4" connection between the panel and disconnect as a raceway (outlet and A/C power wires will be separate and fed from separate breakers). How should I treat this 'bonded neutral' lug?

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    A/C circuits are hot-hot-ground no neutral. When I have occasion to need a neutral in a box like that, I just tie all the neutrals to each other with a wire nut and done. Nowhere is it written every wire must terminate at a bus. Mar 20, 2022 at 21:21

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In your case, it's a ground lug.

You don't need neutral (other than the wire passing through and not connecting to anything here for your convenience outlet.)

It's bonded to the case and therefore cannot be Neutral here, anyway.

It will be clear to any following worker that the green or bare copper wire connected to the lug is a ground.

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Fusible AC disconnects can also be used as service equipment, in which case the NEUTRAL does gets BONDED to ground. That's why the fusible AC disconnect you have has the words BONDED NEUTRAL written on its lugs. You should ignore that notice because you are not using it as service equipment.

In your case, those lugs are to be used as the Equipment Grounding Conductor (i.e. your HVAC ground) terminations. At the disconnect, that ground conductor from your HVAC is cut and terminated at one lug, which connects it to the metal box, then it continues on its way back to the breaker panel with a wire connected at the other lug.

Article 100: Service Equipment - the necessary equipment, usually consisting of a circuit breaker (s) or [switch (es) and fuse (s)] and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.

I added the [] to emphasize the way the NEC should be read such that a Fusible AC disconnect can be used as service equipment. You have a switch and the fuses needed to allow it to be the main control and cutoff of the supply to some application. The pull-out is the switch and the fuses are overcurrent protective devices. In this usage you need to BOND the NEUTRAL, using the two lugs.

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  • Much better, though it may have been easier to edit your previous answer. ;) I updated a bit to improve the NEC quote formatting.
    – FreeMan
    May 16, 2022 at 10:58

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