110.34(A) interpretation

[Dale001289]

Does 110.34(A) apply to VFD's? I always thought it was just for switches, CB's, switchgear and switchboards?

 

[infinity]

This VFD is over 1000 volts?

 

[Dale001289]

yes, its 13.8kV nominal with 7.9kV to ground.

 

[infinity]

Is there ever a scenario where with 13.8 kV you would require working near live parts while this VFD while energized?

110.34(A) Working Space.
Except as elsewhere required or permitted in this Code, equipment likely to require examination, adjustment, servicing, or maintenance while energized shall have clear working space in the direction of access to live parts of the electrical equipment and shall be not less than specified in Table 110.34(A)

 

[Dale001289]

Not sure. We will need to get with operations. Tentatively I believe the table should apply.

 

[Dale001289]

Just found out; the 13.8kV VFD has bolted panels on the backside where the bus is located (i.e. not 'readily accessible') for rear access. I cant see this being worked on energized.

 

[infinity]

Just found out; the 13.8kV VFD has bolted panels on the backside where the bus is located (i.e. not 'readily accessible') for rear access. I cant see this being worked on energized.

That was my thought as well. Wonder if anyone else has an opinion.

 

[jim dungar]

Is there ever a scenario where with 13.8 kV you would require working near live parts while this VFD while energized?

Most gear, like this, is probably dead front construction, so only parts less than 1000V will be accessible while energized. However, while it is being serviced it must be assumed to be energized until it is voltage checked, which requires working clearance.

But, I have laid out equipment rooms where MV clearances were not provided, because the MV components were not accessible until interlocked equipment panels were removed. Working clearance was only provide around the door leading to the MV lugs.