50 Amp RV Outlet: Wire Size and Breaker by Distance

1. What "50 amp" means on an RV

A 50 A RV cord has four prongs: two hots, a neutral and a ground. The coach does not run anything at 240 V in most cases. It splits its 120 V loads across two legs, and each leg may carry up to 50 A. That is why a 50 A service is worth roughly 12 kW (50 A × 240 V), four times a 30 A trailer's 3.6 kW, and not just "20 amps more".

Two consequences follow:

• The breaker is a two-pole 50 A breaker, one pole per leg.
• The neutral is a full-size, current-carrying conductor. When one leg is loaded more than the other, the difference returns on the neutral.

2. Ampacity: the floor, not the answer

The NEC ampacity table sets the minimum. For a 50 A circuit:

8 AWG copper NM-B is rated only 40 A, so a 50 A breaker on 8/3 cable is a code violation, not a gray area. Because outdoor runs are wet locations, NM-B is out anyway; UF-B or THWN-2 in conduit are the usual choices.

3. Two ways to load the wire

Voltage drop depends on how the coach spreads its load.

• Balanced legs: both hots carry the same current and the neutral carries nothing. Each 120 V load only loses voltage on one conductor, which works out the same as a 240 V circuit.
• One heavy leg: the air conditioner, the electric water heater and a space heater can all land on the same leg. Then the current goes out on one hot and back on the neutral, and the drop is measured against 120 V.

We assume a realistic worst afternoon of 40 A on one leg with the other leg lightly loaded. That is an assumption; check your own coach's energy monitor if it has one.

The NEC's informational notes suggest about 3% for a branch circuit. Balanced, 6 AWG meets it with room to spare. On one heavy leg it lands at 3.3%, which most owners accept; 4 AWG is the choice if the coach will be lived in full-time with two air conditioners.

4. Distance table

Each column is the smallest conductor that carries 50 A and stays at or under 3% drop. The copper "balanced" column is what the wire size calculator returns for 50 A at 240 V; the "one leg" column uses 40 A at 120 V.

How to read it: under about 75 ft, 8 AWG copper in conduit is legal and electrically fine, although many installers still pull 6 AWG because UF-B cable needs it anyway and it leaves margin for a bigger coach. From 100 ft on, the one-leg column is the honest one. Aluminum feeders are common for the longest runs because the larger size is still light and easy to pull; terminate them only on lugs marked AL/CU.

5. The ground and the hardware

For a 50 A circuit the minimum copper equipment grounding conductor is 10 AWG. The NEC requires it to grow in proportion when the hots are upsized for voltage drop. Going from the 8 AWG minimum to 6 AWG multiplies the area by 1.59, so the 10 AWG ground has to grow by the same factor, which lands right at 8 AWG copper.

On the hardware side:

• Most listed RV power outlets with a 50 A breaker and a 14-50R accept 6 AWG, and many accept 4 AWG. Check the lug range printed inside the door before you buy wire.
• A 14-50R receptacle alone usually takes up to 4 AWG, but a pedestal is easier to inspect, to protect from weather and to lock out.
• If you will ever want a 30 A TT-30 or a 20 A outlet at the same spot, a combination pedestal saves a second trench.

6. Reading the coach's label and cord

• The cord end and the inlet say 50A 125/250V. That confirms two legs and a neutral.
• The RV's electrical placard or owner's manual lists the main breaker inside the coach, usually a 50 A two-pole.
• If the coach has an energy management system or a smart surge protector, its display shows current per leg. Watch it on a hot day: if one leg regularly sits near 40 A while the other is near 10 A, use the one-leg column in the table.

7. Installation and inspection checklist

• [ ] 50 A two-pole breaker listed for the panel, with GFCI protection (breaker or pedestal)
• [ ] 6 AWG copper hots and neutral, ground at least 8 AWG copper
• [ ] THWN-2 in PVC conduit or UF-B rated for direct burial; no NM-B outdoors
• [ ] Burial depth that matches the wiring method; riser protected where it leaves the ground
• [ ] Receptacle or pedestal with a weatherproof in-use cover
• [ ] Measured at the outlet before plugging in: about 120 V from each hot to neutral, about 240 V between hots, 0 V neutral to ground
• [ ] All lugs torqued to the value on the device label

8. Signs of trouble

• The coach's surge protector reports low voltage on one leg only. That is usually the heavily loaded leg, or a loose neutral.
• Lights dim on one side of the coach when the air conditioner starts, and brighten on the other. That pattern points to a neutral problem, which is dangerous: shut off the breaker and have it checked.
• The plug or receptacle discolors or feels hot. Replace the device and inspect the cord end; heat at a 50 A connection gets worse quickly.

9. Common mistakes

• Wiring a 14-50R with three wires. Without a neutral, the coach's 120 V loads have no return path. All four conductors are required.
• Using 8/3 NM-B or UF-B on a 50 A breaker. The 60 °C rating is 40 A. Cable needs 6 AWG.
• Assuming "50 amp" means 50 A total. It is 50 A per leg, up to 12 kW.
• Keeping a 10 AWG ground after upsizing the hots. Inspectors look for proportional upsizing.
• Splicing an extension cord to reach the pad. A 50 A cord adds its own drop; size the buried run so the coach's own cord is enough.

Case summary

FAQ

Is 6 AWG good for a 50 amp RV outlet? Yes, up to about 100 ft. At 100 ft it drops 2.05% balanced and 3.27% with 40 A on one leg.

Can I use 8 AWG for a 50 amp RV hookup? Only as individual THHN/THWN-2 conductors in conduit with 75 °C terminations, and only on shorter runs. At 100 ft, one leg at 40 A drops 5.1%.

What size wire for a 50 amp RV outlet 200 feet away? For a balanced 50 A under 3%, 4 AWG copper (2.57%), or 2 AWG aluminum. If one leg runs heavy, the copper size grows to 2 AWG.

Does a 50 amp RV outlet need GFCI? Recent NEC editions require GFCI protection for outdoor receptacles at dwellings up to 50 A, so plan for it. Check which edition your jurisdiction enforces.

Can I feed a 30 amp trailer from this outlet? Yes, with a 50-to-30 dogbone adapter. The trailer simply uses one leg.

Different distance or load? Put your own numbers into the wire size calculator, and have a licensed electrician pull the permit for the pedestal.