Electrical Disconnect Switch - Proper Interlocking

[Andre01]

Mike,
We are an OEM of industrial x-ray equipment and will be designing a new platform of machines. Since our x-ray cabinet houses the electrical/electronic equipment we have an access to this equipment via an access door. There is no separate enclosure to house the electrical/electronics. Per NFPA 70 or 79 or UL508A, are we mandated to mount our electrical disconnect (rotary style, non fusable) switch handle on the access door with switch body mounted on a panel in the enclosure? Can we still comply and mount the electrical disconnect on a side wall of the cabinet as long as the access door has closures that require a special tool to open? Does this still fall into compliance? Thanks

 

[petersonra]

Mike,
We are an OEM of industrial x-ray equipment and will be designing a new platform of machines. Since our x-ray cabinet houses the electrical/electronic equipment we have an access to this equipment via an access door. There is no separate enclosure to house the electrical/electronics. Per NFPA 70 or 79 or UL508A, are we mandated to mount our electrical disconnect (rotary style, non fusable) switch handle on the access door with switch body mounted on a panel in the enclosure? Can we still comply and mount the electrical disconnect on a side wall of the cabinet as long as the access door has closures that require a special tool to open? Does this still fall into compliance? Thanks

The NEC (NFPA 70) generally does not apply to the innards of a factory built assembly. You have to accommodate its requirements or your customers will hate you, but whatever is inside the confines of your factory built assembly is generally outside the purview of the NEC.

NFPA 79 is a voluntary standard and thus can't really "mandate" much of anything. However, if you want to claim compliance with it, I think what you want to do is a problem, unless you can interlock the switch with the door.

6.2.3.1 Each disconnecting means mounted within or adjacent
to a control enclosure that contains live parts operating at
50 volts ac (rms value) or 60 volts dc or more shall be mechanically
or electrically interlocked, or both, with the control enclosure
doors so that none of the doors can be opened unless
the power is disconnected. Interlocking shall be reactivated
automatically when all the doors are closed.

I have highlighted in red something that you might want to consider.

 

[starbolin]

... Can we still comply and mount the electrical disconnect on a side wall of the cabinet as long as the access door has closures that require a special tool to open? Does this still fall into compliance? Thanks

What you propose would not appear to meet the requirements under UL508A - 66.1.5.1(b) 'means to prevent restoring power while the enclosure doors are open unless a defeat mechanism is operated; '

The verbiage requires a separate defeat action to restore power anytime the doors are open.