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Thread: today's panel

  1. #1
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    Default today's panel

    Panel 1, (picture 1) the original panel has 4/0 aluminum at the main disconnect (200 amp). Panel 2, directly to the left is fed from a 100 amp breaker in the original panel with #2 aluminum to the 200 amp breaker. Owner stated that this second panel is for the generator which it may be, but has various breakers including a 50 amp breaker that feeds a sub panel in an addition which is picture 3 which has too many throws without a main disconnect. The #2 wire may be okay at the main if it was only feeding the generator breakers, but it is my thinking that it feeds other breakers as well, if so, then this second panel has only 100 amps. I am pretty sure that the owner has no idea what is wired to what in this home.

    Your thoughts are welcome.

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  2. #2
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    Default Re: today's panel

    I don't see an approved transfer switch or interlock to prevent the generator backfeeding the utility.

    Panels downstream of the service equipment in an attached structure do not require a main, nor does the 6 throws come into play.

    As long as the OCPD is correct for the cable feeding that 200 amp breaker in the non-service panel the breaker is just acting as a disconnect. It would not need to match the cable size.
    Good chance that size panel was installed in order to have enough circuit spaces.


  3. #3
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    Default Re: today's panel

    Quote Originally Posted by Jim Port View Post
    I don't see an approved transfer switch or interlock to prevent the generator backfeeding the utility.

    Panels downstream of the service equipment in an attached structure do not require a main, nor does the 6 throws come into play.

    As long as the OCPD is correct for the cable feeding that 200 amp breaker in the non-service panel the breaker is just acting as a disconnect. It would not need to match the cable size.
    Good chance that size panel was installed in order to have enough circuit spaces.

    The transfer switch is not visible in the picture. I realize that the #2 aluminum is okay for the feed, my question is whether 100 amps is adequate for all breakers in this panel of which a 50 amp breaker services another sub downstream with 9 throws.


  4. #4
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    Default Re: today's panel

    The "Six" rule is an exception for power panel boards which are also service equipment which are utilizing multiple disconnects in accord with 230.71.

    Second and Third panels do not have "six" rules (They have "individual" OR up to "two sets" local OR supply side rules - the one-two rules).

    Cannot see enough detail or label to know the limitations or rating of second panel. Assuming 2nd panel is rated for 100 amps, hasn't exceeded its labeled scheduled ratings (stab ratings limitations, buss limitations, etc.) what would be the concern? You haven't passed along a picture of the labeling for any of the panels, especially panel 2. If you are concerned about usage/performance, or tripping due to demand, that would require analysis of useage patterns and load calculations which are beyond the scope for a HI and would be best addressed by a Master Electrician.

    The requirement is up to two, when protected at the supply side of the feeder.

    Third panel appears to be a light and appliance not a power panel board, i.e. 10 percent or more of the circuits are equal to or less than 30 amps. Individual panel protection is not required local to the panel, it may be protected by up to two overcurrent protective devices on the supply side of its feed. See Exception 2 below.

    You have indicated that the third panel is protected at the supply side of its feeder by a 50 amp 2P circuit breaker on a panel preceeding it. As long as this is all the same structure, and the feeder circuit size and wiring are correct and panel rating are properly protected at 50 amps, it would be fine to have up to a limit of 42 or whatever the circut limit is of the panel, even if that third panel was serving an individual residential occupancy (such as a tenant's apartment, as long as the tenants had 24/7 access to the panel). See Exception 2 below.

    408.36 Overcurrent Protection. In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.

    Exception No. 1: Individual potection shall not be required for a panelboard used as service equipment with multiple disconnecting means in accordance with 230.71. In panelboards protected by three or more main circuit breakers or sets of fuses, the circuit breakers or sets of fuses shall not supply a second bus structure within the same banelboard assembly.
    Exception No. 2: Individual protection shall not be required for a panelboard protected on its supply side by two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard. A panelboard constructed or wired under this exception shall not contain more than 42 overcurrent devices. For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively.
    Exception No. 3: For existing panelboards, individual protection shall not be required for a panelboard used as service equipment for an individual residential occupancy.


    Last edited by H.G. Watson, Sr.; 09-08-2010 at 05:58 PM.

  5. #5
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    Default Re: today's panel

    To determine if the feeder is correctly sized you would need to perform a demand load calculation. IIRC someone here said that that is out of the scope of a HI.


  6. #6
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    Default Re: today's panel

    Thanks to all, that was my main concern.


  7. #7
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    Default Re: today's panel

    Second snipped picture, second panel needs four wire feed, grounds separated from grounded conductors separate ground bar. doesn't look like it has been set up for other than service equipment.

    Also Duct tape doesn't belong in electrical cabinet/panel, not even in wiring troughs.


  8. #8
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    Default Re: today's panel

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Second snipped picture, second panel needs four wire feed, grounds separated from grounded conductors separate ground bar. doesn't look like it has been set up for other than service equipment.

    Also Duct tape doesn't belong in electrical cabinet/panel, not even in wiring troughs.
    Look closer - it seems like the angle of the picture obscures a neutral bar. I see the grounded conductors landing somewhere other than where the grounding conductors terminate.

    Also, it appears the duct tape is being used to label circuits, not to secure any connections.


  9. #9
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    Default Re: today's panel

    Anytime they use generators, and have a mess of wires like that, I look very closely for something, anything, to warrant a full check by a licensed and qualified electrician.

    I see a missing knockout in panel 2 and I think a few doubled neutrals, plus untidy workmanship, that's enough.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  10. #10
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    Default Re: today's panel

    Following is a link to EC&M magazine, July 2010, Article by Mike Holt provides a nice summary on Panelboards and switch boards, and covers some of the issues with mentioned.

    The NEC and Switchboards and Panels

    You indicated initially that you felt the occupant could not determine what breakers controlled what. Panel schedules are required, Mike Holt goes into some detail on the subject in the above linked article, you might find some of that language useful when reporting such findings.


  11. #11
    Roger Frazee's Avatar
    Roger Frazee Guest

    Default Re: today's panel

    Thanks for posting that link HG, I'll be able to make very good use of it.


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