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Old 06-18-2017, 03:42 PM   #1
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50 Amp & 20 Amp Service Simultaneously

Hello everyone,

First, let me thank you all for the awesome discussions you've been posting thus far on this forum -- I really, really appreciate your wisdom and experience!

My Challenge
I am interested in installing 50 amp service using an inlet on the exterior of my bus as I'll both want to be able to connect to campgrounds when I find myself in one and because I want to be able to connect the bus to a temp power pole while building a house (e.g., run a dedicated power tools circuit from the breaker box back outside the bus to power tools while building). Yet, I often find myself in places where I'll only have access to the standard 20 amp service that comes via extension cord.

As I understand it, 50 amp service are two 110v connections as well as a neutral and a ground. Each 110v connection powers one side of the service panel. That's all well and good when I have access to 50 amp service; however, if I am plugging into 20 amp service (using two dogbone step downs on the exterior cord, e.g., 50 amp-->30 amp-->20 amp) (dogbone converters link: https://www.amazon.com/dp/B01N8UDPIJ?psc=1) the service panel will then split that 20 amp connection (because of the two 110v cords from the 50 amp inlet) into two 10 amp connections . . . which isn't really enough power to power anything and will likely damage things.

So my question: Is there any way to wire (using some sort of generator setup or something else) the 50 amp inlet to the service panel so that when 20 amps are plugged in they'll only power one pole delivering 110v of conventional extension cord fed service? If so, how? If not, does anyone know of a work around for this issue?

Forgive me if the answer to this question is glaringly obvious ("Duh, dude, you can't do that" or "Yeah, dude, you need part X") . . . I'm pretty new to this.

Any help is much appreciative. I'll augment this post with answers received here as well as an equipment list to assist future posters that may have the same or a similar question. Thanks in advance for your responses! I'll be awaiting them like this:
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Old 06-19-2017, 07:05 AM   #2
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Welcome, wire bus up for 50amp 220v service, then using 2 adapter plugs you can have 110v 15 amp, or 110v 30 amp or 220v 50 amp, this is what I did in ours using these

15 amp to 30 amp adapter


and then
30 amp to 50 amp adapter



this gives of tons of options
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Old 06-19-2017, 07:33 AM   #3
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Thanks so much for the reply, bansil.

I thought this was a reasonable work around but didn't know if when it is brought into the 2 pole breaker box if the 20 amp service would be cut in half . . . 10 amps on each pole.

I guess that's not the case? If not, this is an awesome solution and considerably easier than I was making it.

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Old 06-19-2017, 11:00 AM   #4
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It isn't "cut in half" to go to each pole; you'd just have a budget of 20 amps to use in any combination that suits you. All on one pole, all on the other, or any part on one pole and the remainder on the other.

If it made the load management easier for you, you could put the "critical" stuff on one pole in the breaker panel and configure a dogbone adapter so that when you're using a 20 amp supply only that one pole is powered. It would merely be for convenience, though.
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Old 06-19-2017, 11:06 AM   #5
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Quote:
Originally Posted by family wagon View Post
It isn't "cut in half" to go to each pole; you'd just have a budget of 20 amps to use in any combination that suits you. All on one pole, all on the other, or any part on one pole and the remainder on the other.
Awesome - thanks so much, family wagon! I really appreciate your input and confirmation.
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Old 06-19-2017, 03:13 PM   #6
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When you use an adaptor or stack of adaptors to power a 50A 2 phase box from a 20A single phase source, does the one phase get supplied to both legs of the breaker box in the vehicle? Or do you get to do without every breakered circuit on the right half of your box?
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Old 06-19-2017, 03:26 PM   #7
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It's my belief that most commercially-available dogbone adapters would connect both hot legs in the 50A shore power cord to the same single hot leg in the 20A supply. All breakers would be live.

If a person wanted to buy a piece of cord and a couple ends he could build it that way, or could set it up so that only one of the legs in the 50A shore power cord was live. Back at the breaker box that would be reflected as breakers/circuits alternating live and dead down both sides of the panel (rather than all live on the left, dead on the right).
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Old 06-19-2017, 03:32 PM   #8
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Quote:
Originally Posted by family wagon View Post
Back at the breaker box that would be reflected as breakers/circuits alternating live and dead down both sides of the panel (rather than all live on the left, dead on the right).
Right. I knew that. I don't know why you would think I didn't know that.
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Old 06-19-2017, 03:44 PM   #9
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Yeah, you've been around a while and posted enough that I knew you'd know the bus bars in panels are interleaved. It was just one of those slip-ups that makes a person say "oops." It's all good!
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Old 06-19-2017, 05:13 PM   #10
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Quote:
Originally Posted by dan-fox View Post
When you use an adaptor or stack of adaptors to power a 50A 2 phase box from a 20A single phase source, does the one phase get supplied to both legs of the breaker box in the vehicle? Or do you get to do without every breakered circuit on the right half of your box?
50Amp service is not really "2 phase" it is single phase 220v.

You get 2 "hot" wires (L1&L2) and a neutral. You will measure 110v from neutral to either of the hot wires. You will measure 220v across the two hot wires.

One hot wire serves each of the two "halves" of your breaker panel.

When you adapt down to powering your 50A(220v) connection to run from a 20A (110v) source you would tie the two hot wires together in the adapter.
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