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I currently have a portable generator, an inlet, and an interlock on the main panel to backfeed the panel.

I am moving over to an automatic transfer switch with a standby generator. However, as a backup, I am keeping my portable generator and inlet.

I would like to eliminate the interlock and bring the wires from the inlet in through the automatic transfer switch in the same way that the standby generator connects to it, and select which generator I want to use by way of a DPDT safety switch -- I already own this one.

However, the only circuit breaker that would be sized to protect the wires between the inlet and main panel (through the ATS and safety switch) would be the circuit breaker inside the generator.

Is that allowable by code? Or do I need to put in a hard-wired single-circuit breaker panel before the safety switch to protect the wires?

  • I suppose I could also replace the inlet with one that has an integrated circuit breaker like the Reliance PR50, in lieu of a separate single circuit breaker panel. But obviously I'd like to avoid spending the money on either one if I can avoid it and still remain code-legal. – David Pfeffer Apr 5 '18 at 13:40
  • Will the smaller generator start automatically? I'm just confused of what you stand to gain. Worst case inline fuse boxes are not that expensive and come with a free shutoff switch. They are used in hot tubs etc. – Harper Apr 5 '18 at 21:35
  • @Harper No, it will not start automatically. The inline breaker panel is around $100 and while not expensive, its a cost I rather not spend for no reason. – David Pfeffer Apr 6 '18 at 12:10
  • $100 seems like a lot to me. I just can't wrap my mind around how it is useful to have a manual generator on an automatic transfer switch. Especially if it's a portable generator that is utterly incapable of having all the loads in the house slammed onto it suddenly. So you'll still have to shut all the breakers off, start the gen, cutover, switch loads on one at a time, not switch on certain big loads, that whole routine... – Harper Apr 6 '18 at 12:52
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    @Harper The automatic transfer switch supports load shedding, etc. Since this is a backup to the standby generator, I would like to be able to maintain the same load shedding capabilities if I have to switch to the backup. At 10 running kW/12 kW surge, my portable generator is plenty big enough to handle most of the loads in the house if properly managed by load-shedding. As opposed to right now, where using the standby generator does require having to manage the various loads on my own. It makes sense to use the functionality of the ATS with the portable, manual generator. – David Pfeffer Apr 7 '18 at 16:07
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How about putting the automatic interlock upstream of the interlocked panel you already have?

If that is your main panel you could side-grade it to a sub panel and put a main breaker upstream of the auto-switch.

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    The automatic transfer switch already will be upstream of the panel. It includes a 200A service rated main breaker. The goal here is to eliminate the interlock at the panel and instead bring the inlet in through the ATS as well. – David Pfeffer Apr 5 '18 at 20:10

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