exterior subpanel - mount as semi-flush?

Discussion in 'Electrical Forum discussion & Blog' started by mdr, Jan 5, 2009.

  1. mdr

    mdr New Member

    Messages:
    16
    Location:
    CA
    Hi all,

    Bought a house, built in 1938 with two remodels done in the late 90s. Electrical work was permitted, but is neither rational nor clean.

    I want to add a subpanel for additional circuits (and redoing some of the existing circuits) to bring the house into reasonable shape. The configuration of the house would require an interior subpanel to be very visible from the living spaces - unacceptable according to SWMBO. There are a few places that I could place one, but I've ruled them out as they are far removed from both the circuits and service entrance, and would be very difficult to wire (second floor, no attic access, v. limited crawlspace, plaster walls.

    I'm in N. California, where old construction and the majority of new construction use external panels. My SE is a semi-flush meter/load center combo. I'd like to mount the sub-panel outside, but want a clean installation. Can I place a surface mount panel in a semi-flush configuration? I.E., can a 3R panel be mounted partially extending through siding into a stud cavity? Is this a listing issue?

    I know that I'd have to find an exterior (3R) panel that has sufficient depth to ensure that most of the KOs would be in-wall. Ideally, I'd run the NM right up into the panel from below. (I understand to not exceed the NM clamp listed capacity - 1, 2, or maybe even 3 cables/clamp). However, if need be, I'd be fine running conduit down to a Jbox under the house and making the connections to the branch NM there.

    Thanks for your help.
  2. Billy_Bob

    Billy_Bob In the Trades

    Messages:
    422
    That's the only problem I can think of - that the knockouts would not be deep enough if mounted semi-flush. Also the main wire knockout at the top and any hardware mounted at the knockout for the main wire.
  3. mdr

    mdr New Member

    Messages:
    16
    Location:
    CA
    Thanks for the info, Billy_Bob. I think you're right from a practical perspective - making sure that there is enough depth at the knockouts to access them and their hardware.

    The issue I'm not sure about is whether this violates the panels listed use, which would be surface mount. Probably a q. for the AHJ.
  4. Norcal01

    Norcal01 New Member

    Messages:
    18
    Besides the panel not being listed for semi-flush, a big risk is sealing around the panel to avoid water intrusion & caulking does not cut it, water damage is costly to repair.
  5. mdr

    mdr New Member

    Messages:
    16
    Location:
    CA
    NorCal 01

    Thanks for your response. Given the uncertainty, and the issues regarding mounting/sealing, I've decided to go with a straightforward surface mount. Again, thanks for the response.

    Murray
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