What is the work space requirement in front of a VFD where there is a grounded surface behind the worker? Is the space measured from the front of the equipment with the cover closed or from the inside live parts?
Front, door closed and 36"
Does it make much difference in any specific case? I have always assumed such clearance requirements applied to the surface (unless there is something sticking out a significant distance from that surface) rather than anything inside the enclosure. Thats the only thing that makes any real sense.
I found this at osha.gov:
1910.303(g)(1)(i) Working clearances. Except as required or permitted elsewhere in this subpart, the dimension of the working space in the direction of access to live parts operating at 600 volts or less and likely to require examination, adjustment, servicing, or maintenance while alive may not be less than indicated in Table S-1. In addition to the dimensions shown in Table S-1, workspace may not be less than 30 inches wide in front of the electric equipment. Distances shall be measured from the live parts if they are exposed, or from the enclosure front or opening if the live parts are enclosed. Concrete, brick, or tile walls are considered to be grounded. Working space is not required in back of assemblies such as dead-front switchboards or motor control centers where there are no renewable or adjustable parts such as fuses or switches on the back and where all connections are accessible from locations other than the back.And a table that is the same as the table in the 2002 NEC at 110.26(A)
I come up with 42 inches from the front of the enclosed VFD based on the table..
Ref:
examination,
I had a manager that propped open an 15 kv exposed conductor vault and transformer room door. His excuse was it was to hot and the building was unoccupied and the building was locked. Then he found some professor giving his students a tour of the room. Room stayed locked after that. There were students with in 3 feet from the terminations. I will say that the terms were inside Raychem angle breaks. I never got that close unless I had clothing, gloves, mats and the rest of the safety equipment on and ready to go. All I am saying is there are loons in management and risk management that will if they can put you in harms way. Of course calling their hand usually has extremely bad consequences to your career.
One interpretation of this might be that the distance from the live terminals of equipment mounted on the door of a control panel or other similar enclosure must be measured when the door is open.
Off topic, but related...
Is there a maximum door width allowed on electrical equipment? I know from observation that enclosure manufacturers like Hoffman, Hammond and Rittal do not exceed 36" (900mm) per door, probably because of the rule cited here. However I have seen some custom equipment where the doors are 45" wide and I wonder if they violate some rule. Anyone know?
Pretty much up to the manufacture. CH makes some 42,45, and 48" doors and access panels. Most of it is medium voltage though. Every manufacture that I know has different sized cabinets for those custom installations. My personal preference is door in door or piano hinge. It gets real interesting picking up and trying to mount some of those doors and panel covers. Any one remember the GE panel cover with the Jesus clips? The ones that twisted and used a lever behind the screw head. I spent one year replacing those kind of panels with piano hinge.
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