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Topic: 50-amp 240-volt campground pedestal outlet - explained (Read 721 times) previous topic - next topic

50-amp 240-volt campground pedestal outlet - explained

I put this info together for a friend.  And even though this is well understood by most, I thought it may also be a helpful Forum posting.

50-amp service has 4 wires with two 120-volt HOT feeds.

From this common service we can draw 120 or 240 volts. Each leg is 50 amps @ 120 volts.

Almost ALL 50-amp wired RV's use both sides of the service separately as 120-volts on each leg. Only a few mostly high-end coaches utilize the 240-volt from this same service.

The 50-amp 3-pole 4-wire service is superior to the 30-amp service because of the total amperage available.

30-amp 120-volt service = 3,600 watts
50-amp 120/240-volt service = 12,000 watts

The half round or U is the ground, the one directly below it is the white or neutral and the other two black wires are 180 degrees out of phase with each other are the HOT 120-volt. In reality you have TWO 120 volt split service going into your RV. 

X & Y are interchangeable , red and black wires are hot (live) wires , one wire on the X, and the other on the Y. The neutral (white) and the bare ground wire MUST be on their designated connection.

TO TEST 50 AMP OUTLET USING MULTI-METER PROBES with outlet photo below:
meter red & black probes are interchangeable for AC

touch probes to outlet, correct voltage is noted:

W-Y 120
W-X 120
Y-X 240
G-Y 120
G-X 120
W-G  0

IF Y-X = 0, outlet is usable, but total amps should not exceed 50 amps.

If W-G is NOT 0, outlet should not be used.
neutral & hot are reversed and coach frame & outside skin could be electrically hot and shock you.

120 is ok as 110
240 is ok as 220

Re: 50-amp 240-volt campground pedestal outlet - explained

Reply #1 –
Some common gear to be used in conjunction with a multi-meter are outlet tester and plug-in volt meters.

Many Forum members including ourselves have made creative custom test cords with a 50-amp male plug and two 15-amp female outlets.  Then plugged in gear like these for a quick outlet test before plugging RV into campground pedestal outlet.

Re: 50-amp 240-volt campground pedestal outlet - explained

Reply #2 –
A sheet from our Progressive EMS:
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
Previous: 1983 Airstream 310 turbo diesel, 1979 Airstream 280 turbo diesel
                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: 50-amp 240-volt campground pedestal outlet - explained

Reply #3 –
Looks good Barry.

To muddy up the water I was at a camp ground somewhere the last month (been so many places lost track which one I it was) but instead of having a 120/240V 1 phase Delta service they had a 120/208V 3 Phase Y service so at the site when you checked to ground each of the two legs had 120V but when checking between the hots only had 208.  I was concerned about that for a moment until I realized everything on the coach was set up for 120V and that was what I had.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: 50-amp 240-volt campground pedestal outlet - explained

Reply #4 –
Quote from: turbojack –
Looks good Barry.

To muddy up the water I was at a camp ground somewhere the last month (been so many places lost track which one I it was) but instead of having a 120/240V 1 phase Delta service they had a 120/208V 3 Phase Y service so at the site when you checked to ground each of the two legs had 120V but when checking between the hots only had 208.  I was concerned about that for a moment until I realized everything on the coach was set up for 120V and that was what I had.

Correct, good point Turbojack........... if you checked your neutral current it would have been a little confusing to most....
example;
20 amps leg 1
20 amps leg 2
would be 20 amps on the neutral instead of zero

Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota
 

Re: 50-amp 240-volt campground pedestal outlet - explained

Reply #5 –
I hard wired a progressive EMS in after my auto transfer switch. It protects everything from generator and shore power failures.  I just plug in and never worry about anything!
1998 U270 34'