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I have a 50 amp breaker and space to put it in my main panel. Can I use that breaker or do I need to use a 30 amp does it matter?

I will install a main panel interlock switch and a 30 Amp Generator NEMA L14-30P Power Inlet Box for 4 Prong Generator Cord, 125/250 Volt, 7500 Watts, to plug in the 7000 watt 30 amp generator. I will make the generator a floating neutral as well.

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  • That would be fun. The 50 amp breaker would stay cool as cucumber while the generator is burning up
    – Ruskes
    Jan 26 at 2:52
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    It's not right to put what is presumably 10/3 on a 50 amp breaker, not code compliant UNLESS there was an upstream breaker sub panel with a 30 amp breaker for the genset inlet. I don't even know if that's code compliant, but it would be safe and future proof. As always, breakers are there to protect installed wiring, not devices unless hard wired., Also your genset probably has over-current protection built in, so while what you are asking isn't terribly unsafe, it's certainly not up to code. 30 amp breakers are pretty cheep, just buy one and do it right.
    – George Anderson
    Jan 26 at 5:01
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    Breakers are cheap, don't worry about it, just get the right ampacity for the job.
    – Harper - Reinstate Monica
    Jan 26 at 6:31
  • I presume you have read all the other answers about generators, and know that some form of lockout or transfer switch is absolutely necessary so your generator can absolutely never be connected to the power lines, to avoid endangering line workers. And that you should never use a suicide cord, to avoid endangering yourself.
    – keshlam
    Jan 26 at 14:50

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The generator presumably has a 30A breaker of its own, which protects the generator.

Using a larger input breaker with appropriate gauge wires and 50A inlet (for the 50A breaker on the inlet) is fine. Then if you put in a 50A generator later, no change needed at the panel.

You'll need to make a cord to adapt the 30A outlet to a 50A inlet. If sticking with a 30A inlet you'll need 50A wire to it, and it's a dubious arrangement .vs. a 50A inlet.

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Breakers are cheap

So don't sweat bullets over reusing the 50A. Also, breaker types must match the panel, so if it's handy but the wrong type you can't use it anyway. E.G. if you have a Siemens QP breaker but a Square D panel.

Now if you want to install 50A for future use that's fine. You can use 50A wire (#6 NM if all indoors, #6 UF, or #8 any other copper wire type, or #6 aluminum if you can find an inlet certified for aluminum wire). The inlet will need to match the breaker. NEC 210.21.

A 30A breaker would let you use cheaper and easier to handle #10 wire. Don't know about the cost of a 30A inlet vs a 50A inlet.

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    75 seconds read, it could be shorter, but you are getting better in executive stile without unnecessary side track, but at least you did not complain about made in China
    – Ruskes
    Jan 26 at 8:24
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    c /stile/style/
    – manassehkatz-Moving 2 Codidact
    Jan 26 at 12:08
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    I guess an "executive stile" is that thing which only allows executives into the area and prevents all the peasants/employees from entering ...
    – brhans
    Jan 26 at 14:05
  • Nah, the stile is the upright on a door/window. So the executive stile is the one that’s on a clear path to the top!
    – Aloysius Defenestrate
    Jan 27 at 1:39
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The main thing (since there is the most of it) that a breaker protects is the wire. For 30A that is typically 10 AWG copper cable or individual wires in conduit, for 50A that is typically 6 AWG copper cable, 8 AWG copper individual wires in conduit or 6 AWG aluminum individual wires in conduit.

The second thing is any receptacles or other parts. The 14-30 inlet is almost certainly rated for only 30A.

The last thing is the devices/appliances - i.e., what's at the end of the circuit. This gets interesting. A generator is producing the power, so it realistically can't produce a lot more than 30A if it is rated for 7,000W/30A. It can probably surge a bit (e.g., for motor startup) but that's OK for wires, breakers and everything else too. In addition, the generator very likely has its own over-current protection - e.g., a 30A fuse or breaker on the 30A outlet.

So the big question really is the wire. If you actually have wire that is rated for a 50A circuit then you could, in theory, replace that 30A inlet with a 50A inlet and I think you would be fine. On the other hand, if as is likely the case you only have 30A 10 AWG cable then there is real risk (and code violation) in using a 50A breaker and 50A inlet. That's because the next owner would see 50A inlet and get a bigger generator and overload the wire when in use. But almost nobody upsizes wire unnecessarily, with the exception of using 12 AWG on a 15A circuit, which is fairly common. But 8 AWG on a 30A circuit? Not likely.

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    @Ruskes (a) some people like long detailed explanations, some don't, which is why I sometimes put in a TL;DR; (b) The breaker size defines the circuit - if you put on a 50A breaker, it is now a 50A circuit, not a 30A circuit - which then makes 10 AWG wire a code violation. Similarly, a 15A breaker with 12 AWG wire (larger than needed but common and valid) isby definition a 15A circuit - it isn't a 20A circuit by virtue of the wire any more than a 50A breaker + 10 AWG wire would be a 30A circuit.
    – manassehkatz-Moving 2 Codidact
    Jan 26 at 4:21
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    If installing wire it's a great suggestion to consider oversizing it. When did anybody say "I wish my whole-house backup generator had less capacity!"? When I did my inlet I had 100 ft to cover and a 6500 W generator (for now) -- I used aluminum THHN, 4 gauge I think (?), a 60A breaker in the interlock, and an L14-30 inlet. In my case the inspector agreed that the interlock breaker, being on the load end of the circuit, is really just a switch. The breaker in the generator provides the overcurrent protection. Meanwhile my wiring is all set for a bigger, hard-wired generator in the future.
    – Greg Hill
    Jan 26 at 4:41
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    @GregHill Agreed. With wire that matches (or exceeds) the breaker, and overcurrent protection in the generator, it is only a matter of getting approval of the inlet itself. Which while you would be exceeding specs if you forced a 50A generator output into that inlet (using an illegal adapter cord...) odds are the inlet itself can handle it, whereas the 100' of wire if significantly undersized would not.
    – manassehkatz-Moving 2 Codidact
    Jan 26 at 4:44
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    @Ruskes if 30 seconds is all you want to put into answering a question, Yahoo Answers may be more your speed lol.
    – Harper - Reinstate Monica
    Jan 26 at 6:39
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    30 seconds worth of answer effort matches well with the 30 seconds worth of effort some people put into writing questions. Sadly, both lead to more questions and confusion than necessary.
    – FreeMan
    Jan 26 at 12:49
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Supply breakers can be any size up-to the ampacity of the panel, and that's the role this inlet breaker is taking so 50A is fine feeding from a 30A inlet.

Power comes in through this breaker, the thing downstream from this breaker is a 200A (or whatever size) panel.

The breaker doesn't protect the wiring from the inlet because it doesn't control current into that wiring. that protection comes from the generator.

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