50 Amp receptacle

[INJoe]

Just had a 50 Amp receptacle installed where I plan on parking my 37' fiver. When I got the invoice from the electrician it was for a 220V receptacle. I thought it should be 110V. May have just been a typo on the invoice. Just checking to be sure that it should be 110V. How can I check to be sure?

Joe

 

[Wi1dBill]

Call the electrician and ask, could be a mistake by the person that did the invoice.  Can you check your fuse box and where the electrician added the circuit, one breaker it should be 110v. Two breakers linked together will be 220v.  You'll need a volt meter to test the voltage at the outlet. 
Also, any electrician worth his salt normally would not wire 220v into a 50 amp plug.

But, check it out before you plug in your RV

 

[Tom]

The 50A receptacle is (should be) two 120V circuits, fed from a "split phase" source. Two 120V circuits is the common electricity service required by RVs with 50A connections. We have a couple of articles in our Library explaining this (button in the toolbar above).

I would, however, be sure the electrician didn't install a single 220V circuit, such as would be used for welding equipment. Don't plug your RV in until you talk to the electrician about it.

Edit: Direct link to the articles here and here.

 

[INJoe]

So as I understand the reply's, the 50 amp service is 110 V.

 

[Tom]

If wired as I described, it's two legs of 110V. Measuring voltage between the two legs would show 220V. This is normal for "50A RVs". But you should still verify that's how the electrician wired it. When we had the same service installed at our dock, I warned the not-so-bright electrician that, if he plugged our boat in before I checked it out, I'd chop his hands off.

 

[tvman44]

It actually is a 220 volt circuit, but most RV's only use it as 2-110 volt circuits (no 220 volt appliances inside) but the receptacle is a 220 volt.

 

[sdetweil]

make sure you test it. 2 hot, 1 neutral, 1 ground. nothing less.  I hear that there are still campgrounds with miswired pedestals.  I bought a surge suppressor/tester to make sure. (Progressive SSP-50)

Lack of neutral is gonna mess something up.

 

[Gary RV_Wizard]

No, standard 50A RV power is 220v service. Just about all RVs employ that as a pair of 120v, 50A sources, but what the electrician installs is 220v service. It has a 220v double-pole 50A circuit breaker and twin power lines (4 wires total).

What you need to verify is that you have a 4-prong outlet, what is called a NEM 14-50R receptacle. If there are only three holes in the 220v outlet, do not connect to it! It is almost surely incorrect power for your RV.

Picture of  NEMA 14-50R

 

[sdetweil]

and don't ASSUME cause there are FOUR holes that it is wired correctly either.

 

[John From Detroit]

50 amp is 120/240 volt, thus the recepicial will show on the invoice as 240 volt. This is both normal and proper.

30 amp is 120 volt. only

To test

There are 4 "Blades/pins" the round or "U" shaped one is safety ground

Opposite it is neutral (normally on top as I recall)

Measure from Neutal to either side, you should see 120 volt

Measure side to side, 240 volt

120+120=240

If your voltmeter probes won't make contact (most won't) then you can measure at the main breaker box normally INSIDE the motor home or trailer (or in a basement compartment on the rest)

TURN OFF main breaker and open box

Plug in

CAUTION DANGEROUS VOLTAGE

Measure from the white wire buss to each of the MAIN breaker screw terminals

Should be 120 on each

One breaker to the other 240

Same math as above

Turning off the main protects most of the motor home (All but transfer switch)

 

[oldschool-designs]

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


Please check this site. It will clear up any confusion you may have pertaining to how it works.

The 50 amp RV is a 240 volt circuit split into two legs 180 degrees out of phase, thereby providing two 120 volt hot feeds, one neutral, and one ground, originating from a double pole 240 volt breaker.

This type of 50 amp receptacle can be, and is, used for several other items as well.

Many customers will tell an electrician they need (a) a 240 volt 50 amp circuit installed (b) a 50 amp 110 volt circuit installed, and fail to mention they really want an RV 50 amp circuit installed.

Oftentimes, I have questioned a customer as to what type of "appliances or RV" they are trying to feed, only to have them become rude by saying what a "salesman" told them they needed.

Please check out the site above.

Hopefully, someone will now please pass the salt. 

 

[Oscar Mike]

The photo shows what Fleetwood sent me when I wired my house for a 50A RV Receptacle

 

[carson]

oldschool guy....  best website on RV power I have seen yet  .. a must read and study for all newbies to that sort of thing. IMHO.

 

[oldschool-designs]

oldschool guy....  best website on RV power I have seen yet  .. a must read and study for all newbies to that sort of thing. IMHO.

Thanks for the kind words.

Maybe the moderators would add it somewhere for all the new people. It surely would answer their questions, and save a good deal of threads covering the same questions.

 

[sdetweil]

and maybe help some newbies not make critical mistakes.

 

[oldschool-designs]

The photo shows what Fleetwood sent me when I wired my house for a 50A RV Receptacle

Interesting.....but potential trouble. Notice how they are showing two single pole breakers being used to pick up the hots?

While that will work, you will need to be certain the separate loads are safely balanced within the main breaker box (opposing sides of main versus just stuck anywhere). A double pole breaker will always provide a balanced load. Also the double pole will cost less than two 50 amp 120 volt single pole breakers, and is less trouble to spot if the breaker trips.

BTW, the cord hookup they show would fail to meet or pass code in most places.

 

[Ned]

A double pole breaker will always provide a balanced load

No, that breaker has nothing to do with the distribution of the load circuits.  A double pole breaker is nothing but 2 single pole breakers ganged together.

 

[oldschool-designs]

No, that breaker has nothing to do with the distribution of the load circuits.  A double pole breaker is nothing but 2 single pole breakers ganged together.

A double pole breaker installed into a typical residential main breaker panel feeds each pole of the breaker from a separate side (or leg) of the main bars fed from each leg supplying the panel. This allows each pole to be fed differently, or balanced.

Oftentimes, two single pole breakers are installed onto the same side (or leg) of the feed. On most split bar feed panels, two single pole breakers can be used for a 50 amp Rv circuit IF they are stacked, that is to say if they are together as a double pole breaker looks.

Yes, a double pole breaker is a combination of two single pole breakers, but each pole feeds from a separate feed bar. You are supplying 6000 watts to each pole from a different leg of the single phase panel rather than supplying the full 12,000 watts from the same panel leg.

 

[Ned]

John's diagram is correct, each leg feeds one side of the load center.  I have never seen an installation where both legs were fed to the same side of the load center.  It's a problem that just doesn't arise in real life and if such a thing were done, it would be a direct short between the 2 legs and wouldn't work.  You make a specious argument and are only confusing folks.

 

[weewun]

The advantage of a standard Double Pole Breaker and the reason you should use rather than stacked single breakers is that both CBs will open if one leg is blowing its Breaker, thus increasing the safety of the user.