Thread: AHU disconnect

Where may the disconnect for an AHU be located?

a) In the AHU
b) Next to the AHU
c) Breaker with lock out in electrical panel someplace else
d) (type your answer here)
e) All or any of the above

I was just doing some 'light reading' and found something out I had forgotten. (Which happens a lot.)

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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.

a) In the AHU - means 'not "in" a panel as in "mounted to the panel", but it could be "in" a panel as in "mounted to the interior of the unit and the panel fits over it, and there is an opening where the disconnect goes".

"then I think the correct answer is all of the above."

e) All or any of the above - this incorrect

Note, I should have said you may chose more than one answer, as there may be more than one correct answer and there may be more than one incorrect answer.

If my answer had also considered a thermostat with an off position and within site of the appliance, then would it have been correct?

The thermostat is not considered a disconnect.

Here is what most electricians think their options are:

a) Look at the equipment and see if there is a disconnect mounted in the equipment (by the manufacturer, which means it would - should - meet the requirements for 'unit switches' as the AHU would be listed and labeled).

b) Install a disconnect near the AHU, such as 'in the AHU closet'.

c) Install a lock out device at the breaker, which will now serve as the disconnect and they can 'lock it out'.

d) Any of the above.

a) and b) are correct options, c) is not, making d) wrong.

(Sorry for not making the above letters the same choices as on my other post, but that would have just complicated this post, which is trying to uncomplicate it.)

It wasn't your writing. Though I speak and write English, apparently where reading tables is concerned, it may be a second language.