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Thread: Is this subpanel wired properly?

  1. #1
    DIY Junior Member PLee1980's Avatar
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    Default Is this subpanel wired properly?

    Hello,

    I have a surface mount subpanel in my garage which has been present since I bought the place (I didn't wire it up). I am thinking about adding a circuit to it, so I pulled the cover to take a look at how it's wired and I'm wondering if the panel ground is wired correctly.

    This subpanel sits exactly on the back side of the main panel. There are 6AWG wires feeding the panel from a 60A breaker in the main panel, they've run 6AWG for both 120v legs and the neutral leg, there is no ground wire run or even a ground bar in the subpanel.

    The subpanel is physically connected to the main panel via some type of very short (1-3") metal conduit nipple. I am assuming the "ground" exists by this connection.

    My question is, is this a valid way to ground the subpanel? I know subpanels are not supposed to have neutral and ground bonded, but it is in this panel. Not sure if that is OK since the panels are physically connected via the conduit nipple.

    Any advice? Thanks in advance.


  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    Those white conductors with the black tape need to be of some color different than white, gray, or green.
    The white conductor with the red tape needs the tape removed
    A lug installed to the back of the panel for the green conductor and everything else is okay
    If you plan on installing any more equipment grounding conductors instead of a lug get a terminal bar
    Last edited by jwelectric; 03-22-2013 at 04:08 PM. Reason: fix mistake

  3. #3
    DIY Senior Member Homeownerinburb's Avatar
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    To take what JW told you in a slightly different order:

    The grounding in the panel is incorrect. If you only have one ground wire, the green one in your photo, as JW says, a lug and screw gets it done. I might very well crimp on a ring terminal and use a green 10-32 screw to anchor that green wire. I expect any inspector would be OK with that.

    Just as well to put in a short, four screw terminal bar. The cost is negligable.

    His points on the white wires being used as conductors is of course correct. Years ago the use of tape for smaller gauge wires to indicate their use was permitted, but it has been many years that white is the neutral and nothing else. Likewise green is the ground. Younger electricians will be perhaps surprised when they learn that green was used half a century ago as a ungrounded hot. Brwwwrrr. The lesson is that assume nothing about work other people have done.

    Another code issue that you are unlikely to meet in that panel: a panel needs to be able to be shut off completely with six or less motions of the hand. (Just in case you are tempted to put in a larger panel.)

    You have two two pole breakers in there to feed 240v purposes (I assume they are 240v). Each counts as one motion of the hand. You have two single pole breakers in there, that is two more.

    I am going to be replacing an old Zinsco sub panel in a week or two with modern gear. It currently has eight breakers in it. I will need to put in a 50amp main breaker that will allow all the power going out of that panel to be shut off in one hand motion.

    Go ahead and put in a small terminal bar for your grounds.
    Last edited by Homeownerinburb; 03-22-2013 at 05:51 PM.

  4. #4
    Electrician ActionDave's Avatar
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    More than six disconnects without a main only applies to service panels, not sub-panels.

  5. #5
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by ActionDave View Post
    More than six disconnects without a main only applies to service panels, not sub-panels.
    Unless they are in another building such as a detached garage or storage building

  6. #6
    DIY Junior Member PLee1980's Avatar
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    Thank you both for the info. Sounds pretty straight forward. I'll definitely add a terminal bar and get the ground fixed. I'll work on fixing the wires too, they are short runs anyways.

    I had never heard of the 6 hand motions rule before (learn something new every day).

    The circuit I was wanting to add is for a outdoor spa. I need to feed a small spa disconnect (includes a GFI breaker in the disconnect). The spa requires 50amp service (I haven't purchased the spa yet, but have one I was looking at).

    This panel currently is fed by a 60A breaker in the main panel. The subpanel currently has circuits for:
    1) 240V air compressor (nameplate on the motor is 22A which matches what I am seeing on my ammeter), obviously that runs intermittently, usually for minutes per day. It's got a 30A breaker on it
    2) 240V pool pump (pentair variable speed). At max speed it pulls 15A, but most of the day it runs around 1A. It's got a 20A breaker on it.
    3) 15A plug in outlets in the garage
    4) 15A plug in outlets in the garage

    I'm assuming I'd need to increase the breaker and wire size feeding the subpanel if I wanted to add a 50A spa circuit. How would I go about determining how big I need to upsize the feed?

    Thanks again, I'm learning a lot.

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    How much stuff is likely to be running at once? The breaker needs to be at least that large (and the wire needs to match the breaker). While it is very common to have more branch breaker capacity than feed capacity, it comes down to sizing the main for the anticipated load.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #8
    DIY Junior Member Glennsparky's Avatar
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    A panel feed must be sized for 100% of the non-continuous load plus 125% of the continuous load. With the spa, that's about 100 amps. Which means you'll barely squeak by if you change your hots to #3 copper or #1 aluminum.

    Now there's a label on that panel's cover. It will tell you the panel's maximum capacity. I bet it's 125A. That's #1 Cu or 1/0 or 2/0 AL for the hots. The label will also tell you the main lug's temperature rating and the torque specs. It's very important to torque AL connections.

    The main panel also has a label. You cannot use a breaker larger than the stab rating of the power bus.

    A metal nipple is a perfectly fine ground. But I think it needs a grounding bushing (Insulated Metallic Grounding Bushing) at each end. Then a jumper from each bushing to each ground bar. At the very least each end needs a protective bushing (Plastic Insulated Bushing), whether the pipe's metal or plastic.

    Anyway, you'll have to replace the nipple with something much larger or use a cable with clamps.

    For 100A the ground needs to be #8 Cu or #6 AL. Above 100A up to 200A, #6 Cu or #4 AL.

    These are also the minimum sizes for your neutral. With so much of the load being 240V, the neutral doesn't need to be any bigger.

    All suggestions are based on 75*C or better terminals and 75*C or better wire. Check your labels and listings to confirm.
    Last edited by Glennsparky; 03-26-2013 at 12:32 AM.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Where would you install the spa breaker, or are you also planning to replace that panel?
    Licensed residential and commercial plumber

  10. #10
    DIY Junior Member PLee1980's Avatar
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    Thank you for the detailed info. I hadn't seen the grounding bushings before.

    Regarding the panel feed size, how do they consider things like outlets? I know my main panel has far more "non-continuous" load than feed (200A) if you consider all the outlet circuits (all 20A). Just curious.

    I'll check the stab rating on the main panel as well.

    Quote Originally Posted by Glennsparky View Post
    A panel feed must be sized for 100% of the non-continuous load plus 125% of the continuous load. With the spa, that's about 100 amps. Which means you'll barely squeak by if you change your hots to #3 copper or #1 aluminum.

    Now there's a label on that panel's cover. It will tell you the panel's maximum capacity. I bet it's 125A. That's #1 Cu or 1/0 or 2/0 AL for the hots. The label will also tell you the main lug's temperature rating and the torque specs. It's very important to torque AL connections.

    The main panel also has a label. You cannot use a breaker larger than the stab rating of the power bus.

    A metal nipple is a perfectly fine ground. But I think it needs a grounding bushing (Insulated Metallic Grounding Bushing) at each end. Then a jumper from each bushing to each ground bar. At the very least each end needs a protective bushing (Plastic Insulated Bushing), whether the pipe's metal or plastic.

    Anyway, you'll have to replace the nipple with something much larger or use a cable with clamps.

    For 100A the ground needs to be #8 Cu or #6 AL. Above 100A up to 200A, #6 Cu or #4 AL.

    These are also the minimum sizes for your neutral. With so much of the load being 240V, the neutral doesn't need to be any bigger.

    All suggestions are based on 75*C or better terminals and 75*C or better wire. Check your labels and listings to confirm.

  11. #11
    DIY Junior Member PLee1980's Avatar
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    I'm not sure if it's clear from the picture, but there are four open breaker slots to the left of the existing breakers.

    Quote Originally Posted by hj View Post
    Where would you install the spa breaker, or are you also planning to replace that panel?

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