If, by "in the AHU" you mean as a part of the unit and the disconnect is visible and operated without removing the cover, then I think the correct answer is all of the above.

If you mean that the cover has to be removed to access the disconnect, I don't think so, but I'm not sure. My old Tempstar has this setup so I always cut off the breaker before removing the panel and tripping the switch.

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The only reason some people get lost in thought is because it's unfamiliar territory.
- Paul Fix