Rooftop AC disconnecting means

[dm9289]

In reading thru 440.14 am I correct in my interpretation that the rule is disconnect within sight but thru the exception you can substitute a permanent lock mechanism at the panel

 

[don_resqcapt19]

In reading thru 440.14 am I correct in my interpretation that the rule is disconnect within sight but thru the exception you can substitute a permanent lock mechanism at the panel

Only if you meet the requirements of the exception. Not too many installations will meet that exception as it only applies to equipment that is essential to an industrial process, and a few other restrictive conditions.

Exception No. 1:
Where the disconnecting means provided in accordance with 430.102(A) is lockable in accordance with 110.25 and the refrigerating or air-conditioning equipment is essential to an industrial process in a facility with written safety procedures, and where the conditions of maintenance and supervision ensure that only qualified persons service the equipment, a disconnecting means within sight from the equipment shall not be required.

 

[infinity]

What if the motor is controller by an adjustable frequency drive? Isn't there is an exception to the disconnect rule when if the opening of the disconnect at the motor could damage the drive then the disconnect at the motor can be omitted.

 

[dm9289]

Only if you meet the requirements of the exception. Not too many installations will meet that exception as it only applies to equipment that is essential to an industrial process, and a few other restrictive conditions.

Thanks for sending me reason I put the or in the wrong place in my mind

 

[dm9289]

What if the motor is controller by an adjustable frequency drive? Isn't there is an exception to the disconnect rule when if the opening of the disconnect at the motor could damage the drive then the disconnect at the motor can be omitted.

Sorry for the broken English maybe I just wanted the OR in a different place.

 

[don_resqcapt19]

What if the motor is controller by an adjustable frequency drive? Isn't there is an exception to the disconnect rule when if the opening of the disconnect at the motor could damage the drive then the disconnect at the motor can be omitted.

Not in Article 440 as far as I know.

There is sort of one in 430.102(B)(2) exception, but on the subjective side, especially since you can have a first break control circuit contact in the disconnect that can be wired to tell the drive to coast to stop. This contact opens before the power contacts open and prevents damage to the drive.

 

[brantmacga]

You will also want to verify the nameplate doesn’t specify fuses. Some RTU’s I’ve connected that don’t have an integral OCPD or unit switch will specify fuse protection, in which case you’ll have an HACR rated breaker at the panel, and a fused disconnect at the equipment.


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