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Thread: Bonding / Grounding w/ Metal Reducing Washers

  1. #1

    Bonding / Grounding w/ Metal Reducing Washers

    I just read a post that reminded me of an ongoing dispute with a local AHJ that has yet to be fully resolved.

    This is for a solar electric system. An inverter manufacturer we use has really crappy knockouts in their metal wiring boxes. So we end up installing metal reducing washers, on 3/4" knockouts for our 1/2" EMT (DC side) connections to the wiring box. (all knockouts have been removed)

    The UL listing for metal reducing washers states "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."

    This seems to tell me that ground bushing and jumper is NOT required because the metal reducing washer would meet sec. NEC 250.97 except 4.

    The local AHJ is telling me they are required per NEC 250.97. Am I missing something? Would another code section apply?

    Since it is just a ground bushing and jumper, I had one installed and past inspection. But I have followed up with the AHJ to get clarification, the last message I got simply stated that the AHJ would not be allowing metal reducing washers to be installed w/o a ground bushing and a jumper.

    Can anyone shed some light on this of me?

  2. #2
    Join Date
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    I believe you are correct and the AHJ is wrong. Is your voltage to ground over 250 volts?

  3. #3
    Quote Originally Posted by eprice View Post
    I believe you are correct and the AHJ is wrong. Is your voltage to ground over 250 volts?
    Yes, we are over 250v.

  4. #4
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    IMO the inspector is wrong, just as you pointed out from the white book.

    "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."
    Of course one of the things you have to comply with is the removal of paint under the washers.

    See 250.12

  5. #5
    A little background. This issue was elevated to the Senior Electrical Inspection Supervisor. He used to be the Chief Electrical Inspector till budget cuts came along and eliminated the position. In the crunch, this AHJ seems to have used the tactic of eliminating many positions and making the remaining employees work twice as hard. Trimming the fat is one thing but they trimmed a chunk of muscle too.

    This also came up right after 2 other inspections where I had to elevate issues to his attention. Both of which took about a month to resolve. Since this one was something minor and relatively inexpensive to "correct", it wasn't worth the delay to fight it.

    I am going to chalk this up to Bureaucratic fatigue.

  6. #6
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    Just some feedback from the inspection industry.

    I don't know what state you are in, but in our area you don't have to be a licensed electrician to install PV [you do have to be a contractor, just not an electrician].

    Consequently, with the PV 'boom', some real hack work is being done by folks who don't have a clue about the electrical code; there's a sudden boom of PV 'designers'.

    This 'reducing washer' is one of those areas where many just don't feel comfortable with the project and want to see this bonding performed.

    Please - don't get in my face; I'm giving you some feedback from the industry - I go to monthly electrical inspection meetings with many jurisdictions. This is how they feel, and this is what they want to see.

  7. #7
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    PS

    PS -

    This is from Soares 'Book on Grounding' [a source much more read than the UL White Book on the subject of grounding and a source that is certainly considered 'credible' within the industry].

    Reducing Washers
    "These reducing washers...are not suitable for bonding and should always be bonded around to provide an adequate fault-return path."

    Within the realm of 'what's my comfort zone', an AHJ could certainly hang his hat on this resource as his reason to not allow reducing washers to meet the requirements of 250.97 & 250.4(A)(5).

  8. #8
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    Quote Originally Posted by dana1028 View Post
    Please - don't get in my face; I'm giving you some feedback from the industry - I go to monthly electrical inspection meetings with many jurisdictions. This is how they feel, and this is what they want to see.
    I don't care what 'they want to see' all they can demand is what is in the code.



    This is from Soares 'Book on Grounding' [a source much more read than the UL White Book on the subject of grounding and a source that is certainly considered 'credible' within the industry].

    Reducing Washers
    "These reducing washers...are not suitable for bonding and should always be bonded around to provide an adequate fault-return path."

    Within the realm of 'what's my comfort zone', an AHJ could certainly hang his hat on this resource as his reason to not allow reducing washers to meet the requirements of 250.97 & 250.4(A)(5).
    As far as Sores vs UL, it is not a populaty contest. Sores is wrong here.

  9. #9
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    Quote Originally Posted by iwire View Post
    I don't care what 'they want to see' all they can demand is what is in the code.





    As far as Sores vs UL, it is not a populaty contest. Sores is wrong here.
    I agree here as well, and for some late night reading for the op see UL white book as Iwire / Bob mentioned Pg. 257 (QCIT) and Pg. 259 (QCRV) in the UL White book.
    Greg

    Electrical Inspector in our Nations Capital

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