I install large sortation systems in office supply distribution warehouses across the country. These are like "airport baggage handling" conveyors for UPS type packages to be shipped to your home. We routinely provide large main control panels with 460V-3P-400A power, 100 to 200 motor starters ranging from 1HP-2.1A to 5HP-7.6A, and Programmable Logic Controllers (PLCs) to operate the systems via 115VAC and 24VDC.
Recently, an electrical field inspector in California cited us for a violation of NEC 110.26A and the need for 42" clearance in front of a small 460V-3P VFD enclosure mounted remotely at a 5HP motor (it only had 30"to a concrete wall). This box contains the VFD (since its wiring terminals are not conduit ready) and a 3P non-fused disconnect switch for 430.102 compliance. This VFD enclosure is fed from our main panel via a dedicated 5HP CB overload/short circuit protector and power contactor for control. Upstream of our main panel's 460V-3P-400A master breaker is the warehouse's 460V-3P-400A disconnect in their distribution panel.
I would like some feedback on 110.26 and how it should relate to 460V-3P, 115V-1P, and 24VDC remote devices on a conveyor control system. My understanding was that 110.26 and clearance applied to normally energized main distribution panels, MCCs, panelboards, etc.
If 110.26 needs to generically apply to all wiring remote to our control panels, then I am confused as to how anyone in my industry can properly install and wire a conveyor system. In a material handling system, 24" wide conveyor beds 100ft long are typically laid end-to-end and side-by-side (6" gap) snaking throughout an entire warehouse for miles.
In addition to 3P local motor disconnect switches at each motor, even standard 4x4 junction boxes with 460V-3P 12AWG and blank covers are sometimes buried within a maze of conveyor bed frames, support structures, and protective guards with little to no room, let alone 42" front, 30" wide, and 78" high. It just would not be practical.
Some states, like New Mexico, have even adopted local amendments to NEC 2005 with wording like:
"110.26 (A) Working space. Add: ?Disconnects that do not provide over-current, overload, short circuit, or ground fault protection are not required to maintain the dimensions of 110.26(A)(1), (A)(2) and (A)(3)where adequate space is not readily available and the disconnect is permanently labeled ?Not to be opened while energized?."
I tried to receive further clarification of this from the city of LA, but they were not helpful, probably due to unfamiliarity with our applications.
Thank you in advance for any insight or advice you can provide.
PS: Perhaps someone can also explain to me how NEC justifies the "... 1 meter (3.5 feet)" discrepancy in case I need to move the VFD - do they want 39.37 inches or 42 inches of clearance?
Recently, an electrical field inspector in California cited us for a violation of NEC 110.26A and the need for 42" clearance in front of a small 460V-3P VFD enclosure mounted remotely at a 5HP motor (it only had 30"to a concrete wall). This box contains the VFD (since its wiring terminals are not conduit ready) and a 3P non-fused disconnect switch for 430.102 compliance. This VFD enclosure is fed from our main panel via a dedicated 5HP CB overload/short circuit protector and power contactor for control. Upstream of our main panel's 460V-3P-400A master breaker is the warehouse's 460V-3P-400A disconnect in their distribution panel.
I would like some feedback on 110.26 and how it should relate to 460V-3P, 115V-1P, and 24VDC remote devices on a conveyor control system. My understanding was that 110.26 and clearance applied to normally energized main distribution panels, MCCs, panelboards, etc.
If 110.26 needs to generically apply to all wiring remote to our control panels, then I am confused as to how anyone in my industry can properly install and wire a conveyor system. In a material handling system, 24" wide conveyor beds 100ft long are typically laid end-to-end and side-by-side (6" gap) snaking throughout an entire warehouse for miles.
In addition to 3P local motor disconnect switches at each motor, even standard 4x4 junction boxes with 460V-3P 12AWG and blank covers are sometimes buried within a maze of conveyor bed frames, support structures, and protective guards with little to no room, let alone 42" front, 30" wide, and 78" high. It just would not be practical.
Some states, like New Mexico, have even adopted local amendments to NEC 2005 with wording like:
"110.26 (A) Working space. Add: ?Disconnects that do not provide over-current, overload, short circuit, or ground fault protection are not required to maintain the dimensions of 110.26(A)(1), (A)(2) and (A)(3)where adequate space is not readily available and the disconnect is permanently labeled ?Not to be opened while energized?."
I tried to receive further clarification of this from the city of LA, but they were not helpful, probably due to unfamiliarity with our applications.
Thank you in advance for any insight or advice you can provide.
PS: Perhaps someone can also explain to me how NEC justifies the "... 1 meter (3.5 feet)" discrepancy in case I need to move the VFD - do they want 39.37 inches or 42 inches of clearance?
