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what size breaker should I use inside to support 30 amp RV box outside.? Answered

ok I am adding a 30 amp power box to my house to plug in my RV when friends/family come to stay. then question is I am going to run a new line from the breaker box to the newly installed 30 amp panel outside (with its own 30 amp breaker) what size should the breaker inside be?


First I would check what is available before adding big breakers.
If your main breaker is 40amp, which is pretty much standard these days than you can't add another 30 just for the fun of it.
Once you use a lot in the house AND the RV you main line fuse will trip and that can be very costly.
Around here the line is secured with a 60amp fuse, switchboard with a 40 amp safety switch and breaker.

You are correct to be aware of your service... I concede that I'm a line glutton with 200A service but we have dual 120 VAC Line and and single phase 240 VAC which powers Kitchen electric stove, clothes drier, water heater, welders, several wood working machines, a Hot tub and an RV plug in..

There is no way we can bake and cook a meal while the clothes dryer and micro wave is on.. But then I do not weld while I'm in the hot tub..

Forgot to add a Dual shower steam generator and a soon to come on line Plasma metal cutter..
Not counting an 80W Quadcopter laser terminator ;-/

I'm pointing out that 200 A service may have 400 A worth of breakers added up in the panel. But can never be used at the same time !

All the breakers do is limit wire fire in the walls going to where they are needed..


6 months ago

At least 50 amp if they have an air conditioner..

The breakers are to protecting the wires from overheating and causing a fire in a wall.. You get to decide what gauge wires (ergo) current you place in the main fuse box to the auxiliary fuse box.. It does not hurt to run heavier gauge except in your wallet !

An RV guest might expect to use the AC, the uWave, the lighting and entertainment center all at the same time....

Well, I think I would choose a 40 A breaker to go inside the house, and the reason why is so that when there is an overload, the outside, 30 A breaker, is likely going to be the one that trips first.

I suppose it would be acceptable to use two breakers with the exact same current limit; i.e. both 30 A, but then in the event of an overload, I do not know which breaker would trip first. Also I suppose there is a possibility that both could trip at the same time, and cause both to need to be reset.

I mean, what I am thinking is that with 40 A breaker in series with a 30 A one, the 30A is almost always going to trip first, so that, predictably, that is the first one to check when the lights in the guest's RV go out.

The circumstances needed to trip the 40 A breaker would be more rare, like maybe damage to the line connecting the house's breaker box to the outside breaker box, like if someone accidentally cut into that with a chainsaw.

Otherwise I am guessing loads in the plugged-in RV, will never trip the 40 A breaker, because the 30 A breaker will break the circuit first.