Is this cover yay or nay to meet 250.146(a)[2] ? the corners are not exactly flat.
what say you?
Seems more to it than not being “exactly flat”… 
I say no. The rule says it has to be on a flat, non-raised portion. Like these…
This is what i found.
A listed exposed work cover shall be permitted to be the grounding and bonding means under both of the following conditions:
- The device is attached to the cover with at least two fasteners that are permanent (such as a rivet) or have a thread locking or screw or nut locking means
- The cover mounting holes are located on a flat nonraised portion of the cover
It would be okay if it had a bonding jumper…IMHO.
4 Likes
The cover is not flat where the screws are so a bonding jumper is required.
3 Likes
Why would the corner indents make an electrical difference? The full circumference of each of the four corner screws lands on a flat area of the cover, even though that area is itself recessed. Would this be any less capable of transmitting current than the listed arragement?
The outlet pictured is missing screws, it should have two and probably three, but has just one. The center screw alone will likely get loose over time.
The issue is with the flat interior portion of the cover that rests on the box. The corner will make full contact with the threaded tab on the box in two opposite corners which is sufficient to carry ground fault current.
You’re correct a minimum of two screws are required.
1 Like
Ah, that’s interesting. Flat on the opposite side from what’s visible. There are three types of cover:
- Pure flat sheet
- Deep with four corner indents
- Deep without the four corner indents (thus flat where the screws go)
You’re saying only the first qualifies. The others will make edge contact with the box, plus
contact from case to screw to threads on the box, but no flat to flat contact.
I’m reminded that in the days of old the ground wire was considerably smaller (used less copper) than the ungrounded conductors. That then depends on the OCPD reacting relatively quickly. The ground connector need not transmit full amperage in real world overload situations: just enough to trip the overcurrent device.
Ah, that’s interesting. Flat on the opposite side from what’s visible. There are at least four types of cover:
- Pure flat sheet
- Deep with four corner indents, dimpled
- Deep with four corner indents, no dimples on the indents.
- Deep without the four corner indents (thus flat where the screws go)
You’re saying only the first and third qualifies. The others will make edge contact with the box, plus
contact from case to screw to threads on the box, but no flat to flat contact.
I’m reminded that in the days of old the ground wire was considerably smaller (used less copper) than the ungrounded conductors. That then depends on the OCPD reacting relatively quickly. The ground connector need not transmit full amperage in real world overload situations: just enough to trip the overcurrent device.
Yes, a completely flat cover or the one in the photo that Ryan posted in post #3. The reason these are permitted without a bonding jumper is that the UL listing requires that this type of cover be listed for bonding.
4 Likes
Those are what they call crushed corner covers. As mentioned above they were made to allow bonding without a jumper under specific circumstances.
https://www.hubbell.com/raco/en/Products/Electrical-Electronic/Boxes/Crush-Corner-Covers/c/8465828
- Meet the requirements of the 2020 NEC Article 250.146 (A). No bonding jumper is required for covers with: (1) Crushed corners (2) Two or more device attachment fasteners that are permanent with thread-locking, screws, or nut-locking means (3) Insulating retaining washer removed for at least one device attachment screw
That information is only partially correct. The insulating washer removal is not part of the requirement for the cover in post #3. That would be for a receptacle in an FS style box. From the 2020 NEC:
250.146(A) Surface-Mounted Box.
If a metal box is mounted on the surface, the direct metal-to-metal contact between the device yoke or strap to the box shall be permitted to provide the required effective ground fault current path. At least one of the insulating washers shall be removed from receptacles that do not have a contact yoke or device to ensure direct metal-to-metal contact.
Direct metal-to-metal contact for providing continuity applies to cover-mounted receptacles if the box and cover combination are listed as providing satisfactory continuity between the box and the receptacle. A listed exposed work cover shall be permitted to be the grounding and bonding means under both of the following conditions:
(1) The device is attached to the cover with at least two fasteners that are permanent (such as a rivet) or have a thread locking or screw or nut locking means
(2) The cover mounting holes are located on a flat non-raised portion of the cover
1 Like