2011 nec 250.146

[BSSTG]

Greetings all,

To be compliant with 250.146 (b), I had thought that those receptacles listed as self-grounding never had the little insulating washers as they would inhibit the metal to metal contact. At least they didn't years ago as I recall when I used to work in the trenches. In reading 250.146 (a) however, it would seem to indicate that you could be allowed to remove one of the insulating washers and the receptacle would be considered as grounded as long as it's listed as self grounding? I just don't remember ever seeing receptacles listed as self grounding having insulating washers? Am I missing something here? All of the self grounding receptacles I ever saw never had those washers. It has been a few years since I've even thought about and the subject came up today on a project.

thanksabunch

BS

 

[Gregg Harris]

250.146 Connecting Receptacle Grounding Terminal to Box. An equipment bonding jumper shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box unless grounded as in 250.146(A) through (D). The equipment bonding jumper shall be sized in accordance with Table 250.122 based on the rating of the overcurrent device protecting the circuit conductors.

(A) Surface-Mounted Box. Where the box is mounted on the surface, direct metal-to-metal contact between the device yoke and the box or a contact yoke or device that complies with 250.146(B) shall be permitted to ground the receptacle to the box. At least one of the insulating washers shall be removed from receptacles that do not have a contact yoke or device that complies with 250.146(B) to ensure direct metal-to-metal contact. This provision shall not apply to cover-mounted receptacles unless the box and cover combination are listed as providing satisfactory ground continuity between the box and the receptacle. A listed exposed work cover shall be permitted to be the grounding and bonding means when (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 and (2) when the cover mounting holes are located on a flat non-raised portion of the cover.

(B) Contact Devices or Yokes. Contact devices or yokes designed and listed as self-grounding shall be permitted in conjunction with the supporting screws to establish the grounding circuit between the device yoke and flush-type boxes.

 

[Gregg Harris]

Greetings all,To be compliant with 250.146 (b), I had thought that those receptacles listed as self-grounding never had the little insulating washers as they would inhibit the metal to metal contact. At least they didn't years ago as I recall when I used to work in the trenches. In reading 250.146 (a) however, it would seem to indicate that you could be allowed to remove one of the insulating washers and the receptacle would be considered as grounded as long as it's listed as self grounding? I just don't remember ever seeing receptacles listed as self grounding having insulating washers? Am I missing something here? All of the self grounding receptacles I ever saw never had those washers. It has been a few years since I've even thought about and the subject came up today on a project.

thanksabunch

BS

A standard receptacle with retaining washers can be used to accomplish 250.146 on a surface mounted receptacle provided at least on of the retaining washers is removed.

The listed self grounding receptacle has a metal spring retainer that makes contact with the box to accomplish 250.146

 

[pwood]

bsstg,

are you referring to the square cardboard washer used to hold the screw in place during packing?

 

[BSSTG]

bsstg,are you referring to the square cardboard washer used to hold the screw in place during packing?

That would be correct sir.

I don't get how removing the washer is going to provide a good ground path as it is common for the yoke not to be seated firmly on the box. Additionally, the Code does not address requiring specifically the yoke of the outlet to be firm against the box when the washer is removed thereby ensuring a good ground path. Receptacles that are listed as self grounding are configured where the outlet will be grounded to the box even if there is no good contact between the yoke and box. (at least the ones I've seen in years past) Hence they are listed as self grounding. I don't know why anyone would spend the extra money for self grounding receptacles when you could use a cheapo and just pull off a washer. Maybe I'm missing something here as I don't work with my tools anymore. I'll have to go to the parts house next week and check out how the self grounding outlets are made now and what price differentials there might be out of curiosity. In the above post Gregg is indicating they may be made differently from what I recall.

It's probably not a big deal in the real world but you know these folks on the NFPA panels are very serious about their functions as Code writers. Perhaps one of us should submit a change proposal for more clarity?

BS

 

[Gregg Harris]

That would be correct sir. I don't get how removing the washer is going to provide a good ground path as it is common for the yoke not to be seated firmly on the box. Additionally, the Code does not address requiring specifically the yoke of the outlet to be firm against the box when the washer is removed thereby ensuring a good ground path. Receptacles that are listed as self grounding are configured where the outlet will be grounded to the box even if there is no good contact between the yoke and box. (at least the ones I've seen in years past) Hence they are listed as self grounding. I don't know why anyone would spend the extra money for self grounding receptacles when you could use a cheapo and just pull off a washer. Maybe I'm missing something here as I don't work with my tools anymore. I'll have to go to the parts house next week and check out how the self grounding outlets are made now and what price differentials there might be out of curiosity. In the above post Gregg is indicating they may be made differently from what I recall.

It's probably not a big deal in the real world but you know these folks on the NFPA panels are very serious about their functions as Code writers. Perhaps one of us should submit a change proposal for more clarity?

BS

250.146(B) to ensure direct metal-to-metal contact.

I do not know how to highlight, but it states direct metal to metal "yoke to box"

The self grounding type have a spring steel clip that retains the screw and compresses together when it makes contact with the metal box.

Look at (A) it designates a surface mounted box. Block wall surface mounted conduit and box will allow for direct contact between yoke and box when at least one retaining washer is removed.

Now look at (B) for self grounding for "flush mounted box" ''box must be within a 1/4 of an inch surface'' The spring steel compresses against the screw,yoke and box.

314.20 In Wall or Ceiling. See related UL

In walls or ceilings with a surface of concrete, tile, gypsum, plaster, or other noncombustible material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (¼ in.).

In walls and ceilings constructed of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall be flush with the finished surface or project therefrom.

 

[jwelectric]

5-214 Log #1951 NEC-P05 Final Action: Accept in Principle in Part

(250.146(B))

________________________________________________________________

Submitter: Jonathan R. Althouse, Michigan State University

Recommendation: Insert the words “an effective ground-fault current path” after the word establish in the third line, delete the words “the grounding circuit”. At the end of the sentence delete the words “flush-type boxes” and replace with the words “a grounded metal box” so that the paragraph will read as follows:

(B) Contact Devices or Yokes. Contact devices or yokes designed and listed as self-grounding shall be permitted in conjunction with the supporting screws to establish an effective ground-fault current path the grounding circuit between the device yoke and flush-type boxes a grounded metal box.

Substantiation: This article stresses the importance of establishing an “effective” ground-fault current path, and therefore, these are the words that need to be used in this section. The other issue is that a listed self-grounding device is also permitted to be used for a surface mounted metal box, not just flush-mounted boxes. It should also be made clear that the box must be metal and grounded.

Panel Meeting Action: Accept in Principle in Part

Revise the text of 250.146(B) as follows:

(B) Contact Devices or Yokes. Contact devices or yokes designed and listed as self-grounding shall be permitted in conjunction with the supporting screws to establish bonding the grounding circuit between the device yoke and flush-type boxes.

Panel Statement: Section 250.146(A) addresses surface-mounted boxes. Bonding instead of “an effective ground-fault current path” is the correct terminology. The revision meets the submitter’s intent.

Number Eligible to Vote: 16

Ballot Results: Affirmative: 16

the highlighted in red was deleted