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Pulling a 120 leg from 240, while still running 240.. can it be done.

Discussion in 'General Technical Questions and Answers' started by K7KQA, May 16, 2019 at 3:03 PM.

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  1. K7KQA

    K7KQA Ham Member QRZ Page

    Hello all,

    I have an upcoming rove and I just got my gen back from the mechanic shop.
    It's been awhile since I had messed with it. It's a 9kw diesel genstar.

    On the panel, I can select between 120 only or 120/240.

    Question is can I pull a 120 leg from 240, while still running 240?

    I'm working with an NEMA L14-30 and would like to have a NEMA 5-20 120v outlet and a NEMA 6-20 240v outlet running at the same time.

    I'm not real concerned with load imbalance. Very small load on the 120 leg.

    Here are a couple of images for reference.

    It seems like it's possible but this is something I've never messed with and would appreciate input.

    Thank you for your help guys. I'd like to make this upcoming 6m rove as successful as possible. .-James K7KQA

    240_120.jpg 240_gen.jpg
     
  2. K7JEM

    K7JEM Ham Member QRZ Page

    Sure, just wire it correctly. The 240 volts will be across the two "hot" wires, shown on the outlet at the 10 and 4 o'clock positions, while 120v will be taken from either of those wires as a "hot", and the neutral will connect to the pin at the 1 o'clock position.
     
    K7KQA likes this.
  3. K6BSU

    K6BSU Ham Member QRZ Page

    You noted that your 120 volt load is "low". Unbalance on a 240 volt circuit is expected. The neutral conductor is sized to handle reasonable unbalanced current.

    I'm doing the exact same thing at my shack. Your 240V circuit breaker looks at each leg independently. Just don't exceed max circuit rating on either leg.
     
  4. N4MTB

    N4MTB Premium Subscriber QRZ Page

    Yes, just wire properly. I do it in my shack.
     
  5. WA7F

    WA7F Premium Subscriber QRZ Page

    You should really use a small breaker box to seperate the circuits and protect each load. A small breaker box and a 240V pigtail should do the job. The main breakers on the 240V circuit won’t protect the smaller circuit.
     
  6. W9WQA

    W9WQA Ham Member QRZ Page

    like house wiring huh..
     
  7. N4MU

    N4MU Ham Member QRZ Page

    Yes...I was about to say, "Your home breaker box does it all the time!"
     
  8. K9YLI

    K9YLI Ham Member QRZ Page

    Electric range has a 120 volt oven light and some a 120 volt outlet onthe back panel.. only a 240 volt power cable.
     
  9. N8VIL

    N8VIL Premium Subscriber QRZ Page

    It is ok as long as your not using the ground conductor as a neutral return. You must have a neutral conductor.
     
  10. N8FVJ

    N8FVJ Ham Member QRZ Page

    The 240 volt must have hot, neutral and ground wires or called a four wire 240 volt distribution. If the 240 volt is rated 20 amps, you can wire direct to a 20 amp rated 120 volt AC outlet. If the 240 volts is rated above 20 amps as most are, you will need either a 15 amp or 20 amp circuit breaker to operate the 120 volt AC outlet.
     

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