Reducing washers and grounding Locknuts

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I have a question on application, Can you use a grounding LOCKNUT (not a regular locknut) on "top of" reducing washers per UL, panel manufacturer and NEC and maintain the effective ground fault protection path?
In other words, the grounding locknut bonding screw "digs" into the reducing washer metal for a path through the reducing washer and then to the enclosure panel for the ground fault path.
Assuming you have complied with all the requirements to use reducing washers, ie removing all rings, UL approved ect, ect
 
A grounding locknut may not be necessary or it may not be sufficient. The conditions of installation and the listing of the enclosure will be the determining factors.

1. As per the UL White Book, the reference in that document is (QCRV), p.259 of the '08 version, under the subtitle GROUNDING - Metal reducing washers.

2. The location in the system - such as is it on the line side of the service disconnect or the load side.

3. Is the surface of the enclosure painted or not.

4. How old is the equipment enclosure? Older equipment, I am taking an educated guess, around 7 years or older have different installation requirements for reducing washers (doughnuts as some call them), then do current manufactured products, as the standards for manufacturers producing these products has changed.


With that said:

If you are dealing with a new product and the surface is metallic and not painted.
You will not be required to use a grounding locknut.



Listing issues:

If the equipment enclosure is new and the metallic surface is painted, you will be required to bond around the reducing washers, and a gounding locknut is not sufficient, you will need a bonding locknut or bonding bushing.

If the equipment enclosure is older than 7 years, there are a couple of considerations.
a. have all of the KOs been removed? If not, then mostly bonding around the reducing washers will be required.

b. if the KOs have all been removed, then no bonding will be required as long as the surface of the enclosure is not painted.



Grounding locknuts used by themselves in the "effective ground fault current path" installed with reducing washers does not "bond" both sides of the "path". You will need a bonding bushing or some other means to complete the bonding path.
 

iwire

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Grounding locknuts used by themselves in the "effective ground fault current path" installed with reducing washers does not "bond" both sides of the "path". You will need a bonding bushing or some other means to complete the bonding path.

If UL lists a reducing washer to be the effective ground fault path between an enclosure and an EMT connector I don't believe things change when we add a bonding locknut.
 

roger

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Where are they in the white book? I've look and haven't been able to find it yet.

Iwire posted the following awhile back

2007 White Book OUTLET BUSHINGS AND FITTINGS (QCRV)


Quote:
GROUNDING

Metal reducing washers are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with ANSI/NFPA 70, ??National Electrical Code.?? Reducing washers are intended for use with metal enclosures having a minimum thickness of 0.053 in. for non-service conductors only. Reducing washers may be installed in enclosures provided with concentric or eccentric knockouts, only after all of the concentric and eccentric rings have been removed. However, those enclosures containing concentric and eccentric knockouts that have been Listed for bonding purposes may be used with reducing washers without all
knockouts being removed.


Roger
 

M. D.

Senior Member
William, please avoid deleting your posts, it makes the thread confusing. There's plenty of posts to go around, don't feel bad about posting a second time to simply say, "Never mind, I found it" or what have you. :)

A bit anal about the effects of deleting a post there George???
he made that edit in November:smile:
 

George Stolz

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A bit anal about the effects of deleting a post there George???
he made that edit in November:smile:
That is sooo weird. This thread came up in the "Today's Posts" search last night. :-?

Edit - no, come to think of it, this thread was linked to somewhere else. I must have gotten distracted and forgot when I was. :D
 
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