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I just replaced a 20A generator with a 30A one, and I need to upgrade the generator socket.

The context is a 100% off-grid cabin with two solar panels, a small battery bank, and a 120VAC inverter feeding a few circuits in the house. The generator is used for backup power and to pump water using a 240VAC well pump. Here's the existing setup:

Generator with 20A breaker => 20A cable => L14-20 socket => 12 AWG cable directly to bus bars on a dedicated 100A-rated 8-position panel (Square-D QO Load Center model QO6-12L100DF/S). This panel has two breakers: 20A 1-pole that feeds inverter-charger, 20A 2-pole that feeds the well pump. When I want to charge the batteries, I turn on the generator and flip the relevant breaker; same when I want to pump water. (This was all installed by a licensed electrician who specializes in off-grid work, and it works well.)

All I think I have to do is adjust as follows:

Generator with 30A breaker => 30A cable => L14-30 socket => 10 AWG cable => existing 8-position panel.

Questions:

  • Is this correct?
  • The existing 20A breakers and the downstream wiring to the inverter-charger and well pump can just be left as is, right?
  • My preference would be to add a 30A 2-pole breaker and feed the wiring from the generator through it instead of connecting directly to the bus bars. That way I would have an interior shutoff (in addition to the 30A breaker on the generator itself). Are there any issues with doing that?
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  • My preference would be to add a 30A 2-pole breaker and feed the wiring from the generator through it instead of connecting directly to the bus bars. I think that would be highly preferable to the existing setup. But I'm not a pro. Dec 2 '20 at 22:45
  • Most (all?) generators include an output breaker, which makes providing an inlet breaker (when not needed as part of an interlock) fairly much not a big deal either way.
    – Ecnerwal
    Dec 2 '20 at 23:29
  • What make and model is the panel in question? Dec 3 '20 at 0:18
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Go ahead and put the 30A breaker in, along with a hold down kit

The good news is that your plan with the 30A breaker is feasible, given that you don't have a utility service, which means you aren't subject to the new 230.85 emergency disconnect requirements, which'd require an outdoor disconnect switch or main breaker. However, you'll need a PK2MB hold-down kit for your 30A breaker in order to comply with NEC 408.36(D) (and keep someone from accidentally yanking out a live breaker during maintenance); fortunately, these are not hard to come by.

P.S. your panel is only a six-position panel, which means you'll have only one space left for breakers in it after you put the 30A breaker in, unless you resort to "double-stuff" breakers that is.

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  • Thank you! Appreciate the reference to the hold-down kit. I've seen them before, but never knew what they were called.
    – Bolio
    Dec 4 '20 at 14:24

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