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  1. #1
    Join Date
    Oct 2012
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    Default Having a duh moment

    The first pic is a sub panel for a HVAC unit. They have a three wire romex conductor running to a double pole. The hot and neutral are connected to separate leads on the breaker and the ground to a ground bar. Should there not be a fourth wire for a neutral. The other item is the main panel. The neutrals are under the same screw as the grounds. Should they not be separated. Again this is the main panel.

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  2. #2
    Join Date
    Mar 2012
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    Northern Indiana
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    Default Re: Having a duh moment

    A 240 volt circuit does not require a neutral. In this case the sub is (making an assumption here) grounded through the emt. The neutral buss of the sub should not be bonded to the can. The EGC of the branch circuit should be terminated on a grounding bar. The neutrals in the main should be terminated individually, one neutral per terminal.


  3. #3
    Join Date
    Mar 2007
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    Philadelphia PA
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    Default Re: Having a duh moment

    Is that "sub" panel for a heatpump or AC condenser? If so, it's probably "true" 240 volt and no neutral is required.
    The neutrals in the main panel should not be doubled up or mixed with any other conductors under the same screw. I'll try to attach a handy document about that.

    Attached Files Attached Files
    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  4. #4
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    Default Re: Having a duh moment

    Quote Originally Posted by John Arnold View Post
    Is that "sub" panel for a heatpump or AC condenser? If so, it's probably "true" 240 volt and no neutral is required.
    The neutrals in the main panel should not be doubled up or mixed with any other conductors under the same screw. I'll try to attach a handy document about that.
    Thanks for the link.That is a helpful explanation.


  5. #5
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    Mar 2009
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    Default Re: Having a duh moment

    I would suspect the only problem at the A/C unit is that the ground wire (grounding conductor) got taped white instead of green. The re-purposed neutral in the NM-B (Romex) cable has been properly re-identified. There IS a bit of a question as to the color of the other wire in the NM-B as it looks gray, which is another neutral (grounded conductor) color.

    Technically, the insulation on the supply ground should be green as individual conductors aren't supposed to be re-identified if smaller than #4 but a lot of people, including inspectors, ignore the rule.

    It would also be nice to see a label that indicated only 240 volt loads are permitted in the panel as there are two spaces that could take single pole breakers open.


    I would guess the white taped ground has the same issue on the other end, and where it is connected matters - if not in a main panel it would need to be connected to the ground buss rather than the neutral buss.

    Main panel stuff is just bad workmanship and needs correcting.

    Occam's eraser: The philosophical principle that even the simplest solution is bound to have something wrong with it.

  6. #6
    Join Date
    Mar 2014
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    Ozark, Missouri
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    36

    Default Re: Having a duh moment

    Quote Originally Posted by Brad Richter View Post
    A 240 volt circuit does not require a neutral. In this case the sub is (making an assumption here) grounded through the emt. The neutral buss of the sub should not be bonded to the can. The EGC of the branch circuit should be terminated on a grounding bar. The neutrals in the main should be terminated individually, one neutral per terminal.
    Brad,

    Please tell me the NEC or manufacturer's requirements where you reference that the neutrals in the main panel should be terminated individually. Thanks.


  7. #7
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    Default Re: Having a duh moment

    Quote Originally Posted by Scott Cook View Post
    Brad,

    Please tell me the NEC or manufacturer's requirements where you reference that the neutrals in the main panel should be terminated individually. Thanks.
    I'm not Brad, but did you see the attached document in post #3?

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  8. #8
    Join Date
    Mar 2014
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    Ozark, Missouri
    Posts
    36

    Default Re: Having a duh moment

    Quote Originally Posted by John Arnold View Post
    I'm not Brad, but did you see the attached document in post #3?
    Thanks John,

    That is what I was looking for.


  9. #9
    Join Date
    Mar 2007
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    Chandler, AZ
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    119

    Default Re: Having a duh moment

    Hello folks,

    As I'm not an electrician, I'm having a problem with the rational here. I understand if you are going to loosen a neutral wire lug, sharing a lug with other wires, that the other circuit's, on the shared lug, will loose their neutral reference. (unless you tighten down the lug after you remove only one wire for the circuit you are working on) The paper reinforces the reason "...creates a significant problem when the circuit needs to be isolated"

    So is the problem only when you are removing a neutral wire while doing a repair? Isn't the lug buss all the same potential? If you share a lug, or put it in it's own terminal, it seems that there is no difference to me. Until it is time to do a repair, right?? We all know that joe weekend does a lot of home repairs, so I guess this is just for him as qualified electricians would know about this when working in the panel.

    sorry for also having a DUH! moment. Thanks in advance for anyone that can explain it.

    Dave Hill
    Buyers & Sellers Property Inspections LLC
    WWW.BuyersSellersPi.Com

  10. #10
    Join Date
    Aug 2008
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    Maryland
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    Default Re: Having a duh moment

    Dave,

    If the neutral is one per hole as required only one circuit will be affected. The other connections will not be affected and will continue to operate. If two neutral were in one hole both would be affected until the screw was tightened again. The potential to place 240 on the circuit could also exist.

    All answers based on unamended National Electrical codes.

  11. #11
    Join Date
    Mar 2014
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    Ozark, Missouri
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    36

    Default Re: Having a duh moment

    Quote Originally Posted by Dave Hill View Post
    Hello folks,

    As I'm not an electrician, I'm having a problem with the rational here. I understand if you are going to loosen a neutral wire lug, sharing a lug with other wires,..........

    So is the problem only when you are removing a neutral wire while doing a repair? Isn't the lug buss all the same potential? ...................so I guess this is just for him as qualified electricians would know about this when working in the panel.
    t.
    Not necessarily we had some electricians removing circuits in a dormitory and had to leave the rest of the circuits energized for the students living there. The electricians loosened some neutral screws momentarily to remove one neutral, not knowing the other neutral was on a multiwire branch circuit. In a less than a second the loss of the neutral on the muliwire circuit allowed 240 volts to burn up numerous computers and other devices. The neutral on a MWBC is critical for keeping the unbalanced load (say from a hair dryer) from applying the line voltage from phase A on the neutral side of a smaller load (say a computer) powered from phase B. Same thing happens when a home loses its neutral connection.


  12. #12
    Felix Lechner's Avatar
    Felix Lechner Guest

    Default Re: Having a duh moment

    Hello,

    Another solution to the wiring in the HVAC subpanel is to use the bus bar as an unbonded neutral, and not as a ground. (This is also what Brad wrote.)

    The bonding strip should be removed, and the bare ground wire from the appliance attached to the panel's case. As Brad wrote, proper grounding via the conduit must be confirmed. (I assume this is not in a hospital.)

    Then the label about 240v and tagging the white wire as green, as Bill suggested, would both be unnecessary.

    Felix

    Last edited by Felix Lechner; 04-21-2014 at 12:47 PM. Reason: Re-read previous posts more carefully.

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