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Old 05-22-2016, 10:18 AM   #1
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50 AMP Service 120 or 240

Hello, I am new to the forums so please be patient if I ask dumb questions. I will probably make several rookie mistakes and I apologize in advance.
I have a new Sandpiper that I will use for my retirement. I am trying to set up the electric service for it at the ranch. It requires 50 amp service in order to run everything. By everything I mean both AC units. Texas in the summer the more AC the merrier. I have a lot of electrical experience in my background and I know how to wire up for the 50 amp service. In discussing ( not arguing ,yet) it with my Brother in law he says I am wasting money hooking up the RV to 240 V service that I only need 120 volts to run the RV. My electric experiences tell me that you have to hook up the 4 wire plug per code which would make it 240 volts. Does it matte? Is it better to run the 240 v 50 amp service or is connecting only to a single 120 v 50 amp breaker an adequate solution?
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Old 05-22-2016, 10:24 AM   #2
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A 50 amp RV works off of 120/240 volt split phase service. Hold on and I will edit this post to get you fixed up with some links.

EDIT: here you go, as you can see 50 amp RV service isn't anything unique, as it just utilizes each 120 volt hot leg separately to keep it all 120 volts. It's when people wire the 30 amp 120 volt service as 240 volts when things start burning down.

The main thing to realize that with a TRUE 50 amp split phase 120/240 volt service, you have 12000 watts of total power as opposed to 3600 watts with a 30 amp service....... or 6000 watts if you wire it like your BIL is suggesting.

http://www.myrv.us/electric/index.htm

http://www.myrv.us/Imgs/PDF/50-amp%20Service.pdf

http://www.rvtechmag.com/electrical/chapter3.php

BTW, welcome to the forums and feel free to ask all questions.
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Old 05-22-2016, 10:25 AM   #3
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I would hook up 240 so you can run both ac....each leg is 120 volt for each ac unit....it. Does not cost much more to run an extra wire....if u only run 1 leg 120 you will only be able to run 1ac.


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Old 05-22-2016, 10:31 AM   #4
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You'll have two 120V hot legs on RV 50A service. You CAN get away with a 50A 110V (that's what you'd be doing when using a 50/30A adapter), but I wouldn't recommend it if you're going to run things as a more or less permanent setup. Pulling 50A through a 120V line COULD lead to increased amp draw / heat / low voltage / etc.
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Old 05-22-2016, 11:10 AM   #5
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RV Electrical Systems

This is a good tutoral:
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Old 05-22-2016, 12:46 PM   #6
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Exactly like the links show. 50 Amp service is two 120 vac "legs" (L1, L2) capable of 50 Ampere each or 100 Ampere total; called single-phase 240 vac. One phase comes into the power companies transformer and it produces the 180 degree out of phase outputs. 240 vac is available but wired in the panel to only deliver two separate 120vac legs in 99.9% of the RVs out there. They tell me that some RVs, although quite rarely, actually have one or more 240 vac appliance.
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Old 05-22-2016, 01:19 PM   #7
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120 or 240

If you run 240 volt to the Rv you will burn up your charger converter or your charger inverter you run 50 amp 120 volt. You have nothing in a Rv that operates on 240 everything is 120 volts. 50 amp breaker single pole with # 8-2 wire if your not running the service to far if it is a long run you will need to upgrade the wire to 6
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Old 05-22-2016, 03:20 PM   #8
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That's true if you try to wire a 30A RV plug like a 240V dryer outlet. A 50A RV will have two 120V hot wires and the converter will be split between them so it won't see 240V. You'll need a double pole 50A to do it and get full power.
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Old 05-22-2016, 04:48 PM   #9
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Quote:
Originally Posted by raspivey View Post
That's true if you try to wire a 30A RV plug like a 240V dryer outlet. A 50A RV will have two 120V hot wires and the converter will be split between them so it won't see 240V. You'll need a double pole 50A to do it and get full power.
50 amp 120/240 volt split phase service is one of the most confused and often misunderstood things we encounter on the forums. It's more accurately explained in the links provided in my post #2 above.

A 50 amp service going to the RV consists of TWO 120 volt legs (each at 50 amps), a ground wire, and most importantly a shared neutral wire. It's partly due to this common neutral shared, that makes the doublepole breaker trip if one line see more than 50 amps, so as to not burn up the neutral. This is due in part to load balancing, and is again explained in the links of post #2.

Unless the two 120 volts lines are wired to an appliance, then they stay separate and thus 120 volts.

At the electrical distribution panel inside the RV, it will have TWO sides to accommodate the two hot legs, and thus also keep everything it feeds from that point forward as 120 volts.

You may have say the first air conditioner, the electric outlets, and the water heater being provided power by the L1 side.

Then the L2 side may provide power to the second air conditioner, microwave, and the converter.

The converter (which converts 120 volt AC to 12 volt DC to provide power to the DC stuff), will NOT be split in any way. It will receive 120 volt AC from only ONE side (either the L1 or the L2) and not split between anything.

These pics below may help get a clearer handle on it that show the 120/240 volt split phase outlet (feed) and then the electrical distribution panel inside a 50 amp RV:






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Old 05-22-2016, 05:01 PM   #10
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Originally Posted by wmtire View Post
The converter (which converts 120 volt AC to 12 volt DC to provide power to the DC stuff), will NOT be split in any way. It will receive 120 volt AC from only ONE side (either the L1 or the L2) and not split between anything.
I just realized I said converter....oops. I had meant to say panel. Thanks for the clarification.
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Old 05-23-2016, 12:07 AM   #11
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What you get with 50A service is 2 hot lines each capable of supplying 50 amps of current. The circuit breaker for these 2 legs is connected together so if 1 trips then they both trip.
With 30A service you only get 1 hot line capable of supplying 30 amps of current.
A 30 to 50 adapter just takes that 1 30 amps lines and supplies it to both of the input lines to the RV. You now have a total of only 30 amps being split up to a system that is setup for a 50 + 50 service.
This is actually the way most houses are wired (the 50 amp service that is), you have 2 phases of 110v going to the panel and sent individually to the house outlets. To get 220v you send both lines to the properly wired outlet.
If you were to connect a voltmeter to those 2 hot lines it would read 220v. Connecting the voltmeter between either of those lines and ground or neutral will read 110v.
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Old 05-23-2016, 07:37 AM   #12
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Quote:
Originally Posted by tdazbell View Post
Hello, I am new to the forums so please be patient if I ask dumb questions. I will probably make several rookie mistakes and I apologize in advance.
I have a new Sandpiper that I will use for my retirement. I am trying to set up the electric service for it at the ranch. It requires 50 amp service in order to run everything. By everything I mean both AC units. Texas in the summer the more AC the merrier. I have a lot of electrical experience in my background and I know how to wire up for the 50 amp service. In discussing ( not arguing ,yet) it with my Brother in law he says I am wasting money hooking up the RV to 240 V service that I only need 120 volts to run the RV. My electric experiences tell me that you have to hook up the 4 wire plug per code which would make it 240 volts. Does it matte? Is it better to run the 240 v 50 amp service or is connecting only to a single 120 v 50 amp breaker an adequate solution?
Straight from the links provided: "It is a misconception that this 50-amp RV service is something special. This service is a STANDARD 120/240 50-amp 3 pole with 4 prongs used for numerous applications. "
Unless I am totally misunderstanding something here, a double pole 50 amp breaker is what you need to wire it. Hence, 240 volts.
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Old 05-23-2016, 09:47 AM   #13
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Quote:
Originally Posted by jk510 View Post
What you get with 50A service is 2 hot lines each capable of supplying 50 amps of current. The circuit breaker for these 2 legs is connected together so if 1 trips then they both trip.
With 30A service you only get 1 hot line capable of supplying 30 amps of current.
A 30 to 50 adapter just takes that 1 30 amps lines and supplies it to both of the input lines to the RV. You now have a total of only 30 amps being split up to a system that is setup for a 50 + 50 service.
This is actually the way most houses are wired (the 50 amp service that is), you have 2 phases of 110v going to the panel and sent individually to the house outlets. To get 220v you send both lines to the properly wired outlet.
If you were to connect a voltmeter to those 2 hot lines it would read 220v. Connecting the voltmeter between either of those lines and ground or neutral will read 110v.

That sure keeps it simple
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Old 05-23-2016, 10:44 PM   #14
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50 Amp Service 120 or 240

Thanks to every one for the help. I knew from my prior experience working on industrial electric project that 2 50 Amp breakers and wiring 2 120 volts lines was correct. I have never own a big RV like this so I was not sure about how that affected the RV circuits. I had already purchased all the correct wires and breakersso I will get this job off my list. Once again thanks to everyone.
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