Connect with us

Portable Generator Wiring to Transfer Switch

Discussion in 'Electrical Engineering' started by Pop, Nov 21, 2005.

Scroll to continue with content
  1. Pop

    Pop Guest

    Cross-posted; f'ups to a.h.r. So if you read it once, you read
    'em all.

    I'm (finally) getting around to installing a transfer switch for
    my portable generator. The purpose of my post here is to check
    for any NEC violations, or safety issues, whatever. I've had the
    switch over two years so I think it's time I installed it.
    I'll pass my final decisions past my local code enforcement
    officer so it'll all be done to code, and will be inspected.
    From my initial contact, he wants to see a schematic
    representation of the installation in a line drawing. No
    problem there.

    Country: US. Very rural area, lose power often.

    I have a 5,000W generator with an L5-30 120/30A receptacle and
    L14-20 120/240V 20A receptacle.
    I plan to use the 120/240 so I can run the well pump, 1 HP,
    240V submersible, so I need the split phase output. There are
    no other 240V appliances other than the dryer, which I'm not
    worried about running. It'll be about the only thing can run
    when it's needed, but that's OK; one or two lights after the pump
    gets started and I should be fine current-wise. I'm not worried
    about managing capacity. The generator DOES have breakers, and
    it's an industrial grade generator for what it's worth.
    The Transfer Switch, a 7,500 watt device, has a 125/250V 30A
    plug on it to connect to it.
    I'm not planning to use an outdoor Power Inlet Box, simply
    1. There is a disconnect at the generator itself, and the
    generator will be located right beside the power meter when it's
    used, under an overhang, but completely outdoors and highly
    2. It costs money and only about 7-8 ft of cord are required

    Here are my questions:
    -- Can I avoid use of the outdoor Power Input box and still
    satisfy the requirement for a manual disconnect? As I said, the
    cord is simply plugged and unplugged from the generator itself.
    Inside of course, the cord can be pulled from the transfer
    switch also. The transfer switch is mounted right next to the
    mains breaker box.
    Reading the requirements it's confusing; they say a manual
    disconnect is necessary, and the box is an option item, but ...
    why? I could see if it were direct-wired to the generator, but
    it's not. I can't find an allowance for the generator manual
    disconnect, in other words.

    -- I'll have to use a 20A 4-wire cord with the L14-20 plug on
    one end for the generator, and a 125/25-V 30A receptacle on the
    other end to connect to the transfer switch.
    Any problems with using 20A wiring on a 30A receptacle? Can't
    see why there would be.

    -- I'm also planning to run the cord into the house through a
    piece of steel conduit to manage passing thru the wall.
    Inside, the cord will just run up the wall to the transfer
    switch and plug in there. The transfer switch is right next to
    the breaker box.
    Outside the wall it'll connect to the generator and i'll build
    a small box to house the cord neatly and out of sight when it's
    not in use. Might be a good idea to padlock it away from kids
    etc., hadn't thought of that, but that's why I'm posting my
    quest, to pick up details like that, too.

    All the diagrams I see indicate an outdoor power inlet box
    outside and a junction box inside. The run for the cord is so
    short I'm trying to bypass using either of those.

    -- And, one last question: If I read things right, I do NOT use
    the ground strap on the generator to attach to the house ground,
    right? It's right there and would be easy to use a clamp-on, but
    from what I read it's not required and in some ways not
    desirable. It derives its earth from the breaker box in this
    case, and not the ground rod. Right?

    Thanks for any comments or thoughts you may have; I appreciate
    your taking time to consider my post. I've tried to keep it


Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day