TAP RULES DISCONNECTS

[ohmhead]

Question I have a air handler unit with 4# 10 hp motors all operate at the same time all go off at the same time there all mounted in one enclosure and function as one .
each has a freq drive and each drive has fuse protection factory installed inside them . Now I have one feeder that supplies power to this AHU unit the taps to each freq drive will be the same size as feeder. If I used smaller taps off the feeder do I need fused disconnects . NEC article 430.102 exc. 2# says one disconnect for a group of controllers that drive one machine . Is this one machine in my case is a AHU unit a machine ?

 

[broadgage]

IMHO, it would be reasonable to consider the AHU to be a machine.
In addition it seems reasonable to use smaller wire tapped of the feeder, to supply each VFD. The smaller wire would be protected against overload by the fuses in or adjacent to the VFD, a long term overload cant happen. A short circuit is a (fairly remote) possibility, but the larger upstream fuses would protect against short circuit.

 

[ohmhead]

IMHO, it would be reasonable to consider the AHU to be a machine.
In addition it seems reasonable to use smaller wire tapped of the feeder, to supply each VFD. The smaller wire would be protected against overload by the fuses in or adjacent to the VFD, a long term overload cant happen. A short circuit is a (fairly remote) possibility, but the larger upstream fuses would protect against short circuit.

That's my plan but my superior has said he wants fused disconnects because of the tap reduction from the main feeder . I was thinking why is this necessary when you have a fused VFD plus it has a disconnect built in with the fuses internal. I thought maybe the tap rule needed to protect the smaller wire at what length if it was less the 8 feet from a gutter to VFD . So let me ask is there a rule that we missed as far as the tap from feeder reducing to say a smaller wire to four motor VFDs .