50 amp question

[Fr8Train]

My 5er is a 50 amp, is it 120 or 240? My plug has 2 blue led sometimes only one is on and other both are on. Am curious as to if the leds are showing one or two legs.

[WinnieView]

Two 120 volt legs.

[norty1]

It's a double 50a feed. It can be used for 2- 50a/120v or 240v if needed. Most rv's use the 120v legs.

There are many differing opinions and discussion about this. I think much of the disagreement is on the terminology.

These threads tend to not last to long so be nice.

[Hoppy220]

If I understand it right, the simple answer is the the 5er is 120 (there are no 240v circuits inside the 5er) now the more confusing part, your power cord takes 240v. Once inside the 5er one leg of the 240 feeds one side of the breaker box, and the other leg feeds the other side. So the 5er splits the 240 input into 2 separate 120 outputs. That's should make it clear as mud for ya

[GHen]

Your right, it is hard to explain. To confirm, everything in the RV is 120v. Shore power using a 50amp plug brings 2 120volt circuits (legs)to the RV. The A/c units are both 120volt. If you have two A/C units, one runs off of one of those 120 volt circuits and the other runs off the other 120volt circuits.

Sorry if this confuses the issue, but this is how I learned it: Another way to describe it, when at home, you can plug a extension into the RV and run everything, except for the second A/c. If you run a second extension to the RV you theoretically could power the second A/c from that one. The 50 amp shore power cable is like two 120volt extension cords in one cord with heavy wire to handle the big loads.

[wags999]

Some 5ers do use 240 for dryers etc. But as others have said, the receptacle is wired the same as a 240 volt 50 amp line. Yes, once inside your RV each side (120 volts) will power part of the breaker box, same as your brick and stick home. Almost all circuits inside your Rv are 120.

[GHen]

Originally Posted by wags999

Some 5ers do use 240 for dryers etc. But as others have said, the receptacle is wired the same as a 240 volt 50 amp line. Yes, once inside your RV each side (120 volts) will power part of the breaker box, same as your brick and stick home. Almost all circuits inside your Rv are 120.

But the 240volt dryer Has two 120volt power lines running to it, so they call it 240v. If you check it with a volt meter, everything will show 120volt. True 240volt circuits, where the volt meter shows 240volt are normally only commercial appliances.

[GHen]

Sorry, I don’t mean to sound like I’m not agreeing with you, it’s just hard to explain. I have completely wired two of my homes, but I’m still a rookie.

[Fr8Train]

Originally Posted by GHen

But the 240volt dryer Has two 120volt power lines running to it, so they call it 240v. If you check it with a volt meter, everything will show 120volt. True 240volt circuits, where the volt meter shows 240volt are normally only commercial appliances.

I had that exact same thought. You beat me to it. Even in the commercial 240v you’re looking at 3 phase.

[wags999]

Originally Posted by GHen

But the 240volt dryer Has two 120volt power lines running to it, so they call it 240v. If you check it with a volt meter, everything will show 120volt. True 240volt circuits, where the volt meter shows 240volt are normally only commercial appliances.

Duh. Yes you only see a 240 volt line in 3 phase.. where you have two 120 volt lines and one 240 volt lines.. used commercially only.

If your powering your dryer with 240 line it does mean you have 2 120 volt PHASED lines coming to it. That IS the definition of a 240 volt system. If you check across the two 120 volt lines you will get 240 volts because it's phased. Even commercial dryers are wired exactly the same. Some industrial equipment, like the sander and edgebanders I had uses 3 phase and yes one of the lines IS 240 volt.

[norty1]

This is going great, no name calling and insults!!

[Hoppy220]

Originally Posted by norty1

This is going great, no name calling and insults!!

You big dummy.....😁 sorry, couldn't help it

[bigironcoder]

A "properly" wired 50 amp RV campground outlet should measure 120 volts from both left and right blades to Neutral (bottom blade) or Ground (top round contact). 240 volts between left and right blades. 0 volts between neutral and ground. Most good surge protectors will measure & monitor that for you.

[wags999]

Originally Posted by bigironcoder

A "properly" wired 50 amp RV campground outlet should measure 120 volts from both left and right blades to Neutral (bottom blade) or Ground (top round contact). 240 volts between left and right blades. 0 volts between neutral and ground. Most good surge protectors will measure & monitor that for you.

Yep

[WinnieView]

Originally Posted by wags999

Yep

You must be an electrician.

[wags999]

Originally Posted by 2008Seneca

You must be an electrician.

In my previous life... but we do work at campgrounds so, still involved in it.

An RV is wired much like a home, but with 50 amp service rather than 100 or 200 or 400 amp service in a stick and brick.. 2 120 volts legs coming in, some circuits may use both legs ie 240 volt circuit, and most using one leg at 120 volts. 3 phase is used mostly in industrial applications, it is 480 volt service.. one 240 and two 120 legs.
What is important to understand is, a 30 amp service gives you 3600 watts of power available, at 120 volts. A 50 amp service gives you 12,000 watts of power available at 120 volts...Huge difference. Plugging a 50 amp into a 30 amp with adapter will give you about 1/3 the power you would have if you used 50 amp.. Plugging a 30 amp service into a 50 amp receptacle give you only 3600 watts of power. There is a slight chance of damaging your cord, since potentially your cord, if shorted out, could pull 50 amps before tripping the pedestal breaker, it won't hurt your RV as your RV breaker box will limit your usage to no more than 30 amps of power..

[CampNow]

Originally Posted by bigironcoder

A "properly" wired 50 amp RV campground outlet should measure 120 volts from both left and right blades to Neutral (bottom blade) or Ground (top round contact). 240 volts between left and right blades. 0 volts between neutral and ground. Most good surge protectors will measure & monitor that for you.

To piggyback further on what bigironcoder said: There are two 120 volt AC "phases", a neutral, and a ground on a typical 50 amp RV plug or pedestal (total of 4 circuits). Each of the two 120 volt AC phases (legs, waveforms, feeds, or as bigironcoder called them, L&R "blades") are 180 degrees out-of-phase with each other (on an oscilloscope one phase goes 120 volts positive at the very same time as the other phase goes 120 volts negative). That's why you'll measure a 240 volt difference between these two phases. You should measure 120 volts AC between either phase and neutral. Each of these phases are capable of supplying 50 amps of current (6k watts) at 120 volts AC, for a combined total current of 100 amps (or 12k watts) at 120 volts AC. That's why there are two 50 amp breakers (one for each phase or leg) on an RV 50 amp power panel and/or pedestal.

FYI, if you have a bad neutral (with 50 amp RV service) voltage can potentially spike as high as 240 volts inside your RV. Unfortunately, a bad neutral may sometimes only rear its ugly head while under load. A simple voltage check (that some make) before connecting power (with no load) at a campground may show everything is fine when in reality it's not. Needless to say, bad neutrals (especially with 50 amp RV service) are a very bad thing. Another good reason to invest in a good EMS (electrical management system).

[CoCanCarv]

You do not have a combined current of a 100amps on a 50 amp breaker. Each phase of that breaker will not exceed 50 amps for more then six seconds overload and .01 seconds of over current.

[wags999]

Originally Posted by CoCanCarv

You do not have a combined current of a 100amps on a 50 amp breaker. Each phase of that breaker will not exceed 50 amps for more then six seconds overload and .01 seconds of over current.

You do have 100 amps at 120 volts available with a standard 50 amp RV circuit. 12,000 watts of available power at 120 volts. Each leg is 50 amps at 120 volts, 2 legs..hence 100 amps at 120 volts...

[norty1]

The ones I have seen have a double 50a breaker.

If either one exceeds 50a, both should be interrupted by the pedestal breaker.