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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?

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    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. Apr 5, 2018 at 21:35
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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. Apr 7, 2018 at 16:07
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    The NEC requires standby generators that automatically transfer to be able to carry the full load of the building. It should be properly sized so there would be no load shedding. Having a switch that would defeat the automatic transfer doesn’t make sense. You might as well have a manual transfer switch then. A portable generator requires interactive load management, a standby generator is not supposed to require any intervention.
    – ArchonOSX
    Dec 3, 2019 at 11:06
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    @ArchonOSX I didn't discuss this in the original question because it isn't part of the original question. Rather than answering the original question, you're discussing something unrelated. However, yes, Dynamic Load Shedding is the Generac brand name for Load Management. There is no additional panel. It dynamically peels off larger circuits that are wired through special modules interactively to ensure that the generator's total capacity is not exceeded, which makes it comply with code. Dec 6, 2019 at 19:19
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    @jay613 I found a 50 amp generator inlet from Reliance that has an integral Square D breaker slot. That is one of the inputs to the safety switch, and the standby generator is the other input. The safety switch feeds the ATS. The AHJ thought it was acceptable and approved the permit. Nov 23, 2021 at 13:14

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I found a 50 amp generator inlet from Reliance that has an integral Square D breaker slot. That is one of the inputs to the safety switch, and the standby generator is the other input. The safety switch feeds the ATS. The AHJ thought it was acceptable and approved the permit.

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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. Apr 5, 2018 at 20:10
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The transfer switch needs to be sized for the load.

this is code. If the panel that is being interrupted is 200 amp the ats has to be 200 a not just the size of the generator.

The ability to load shed is ok but the switch it self needs to be able to isolate the mains power. If the main service drop is 200a the switch will be 200a.

If the switch has load shedding capability the generator only has to be sized to the load. But the switch has to carry everything the panel is rated for it is isolating.

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