Explanation of 50 amp service?

[scottyb]

Since my original post was moved to a new topic, I am editting it somewhat. What's the difference between 50A and 220/240v? seems to me they are one and the same. Don't they both deliver 120v from two different legs? I know that a 50A plug meters 240V from one hot to the other. I thought it was just how the power was used once it is delivered to the appliance or trailer. Our trailers only use both legs but only one leg at a time and a 220V appliance uses both legs together. Just curious.

 

[jimtoo]

I moved your question to it's own area.

Jim M

 

[TedS]

Our trailers have two 50-amp circuits. Both sides are used at the same time, but separate.
A 220v system uses both legs together.

 

[scottyb]

Our trailers have two 50-amp circuits. Both sides are used at the same time, but separate.
A 220v system uses both legs together.

I understand that. My question is what is the difference in the service. This came up on another topic, where people were discussing whether 240 v service was introduced to someone's RV, therefore resulting in severe damage to the RV. My question is; are not all 50A services delivering 240V to the RV?. It's just a matter of how the RV's electrical system distributes the 2 x 120V legs. It can either be distributed as 2 x 120V or 240V. It's not the electricians fualt that wired the service.

 

[danemayer]

Scottyb,

I think you're correct that the 50Amp outlet is the same. But on a 50Amp outlet, if there's a problem with the neutral, you can damage the appliances in the RV.

Also, sometimes people use 30 amp outlets, which if not wired properly for RVs, may be 220V instead of 110V. Someone recently posted about this exact problem.

Look at the 50Amp, 30Amp, and Open Neutral pages on this site for more info.

 

[mattpopp]

With a 220v each leg supplies the 110v. But each 110v leg must come from a separate buss. They can not come from the same buss. As for the 50amp Rv its more like a 30amp and a 20amp circuit. While each 110v leg could come from the same buss but each leg is also paired with a neutral wire.

The 2nd leg on my 50amp service only runs the 2nd a/c. So when I use the 30 to 50 amp adapter at the parks I lose the 2nd a/c function as the 50amp service only has one hot leg in it while using the adapter.

I power my 50amp Rv from my garage. What I ended up doing was installing a 4 way outlet. Each socket (pair of plugs each) is wired to its own 30amp breaker on the same buss. I have a converter box that will plug into one outlet on each socket. The box has the proper 50amp outlet that I then plug into.

It may seem like I should have just wired a 50amp Rv outlet but I don't have any spare slots to add breakers in the breaker box. I did not want to sacrifice the 110 outlets for something I rarely use.

 

[hoefler]

With a 220v each leg supplies the 110v. But each 110v leg must come from a separate buss. They can not come from the same buss. As for the 50amp Rv its more like a 30amp and a 20amp circuit. While each 110v leg could come from the same buss but each leg is also paired with a neutral wire.

Not true. Both legs are 50 amp, and they can be on the same buss. The only difference would be, if you actually had a 220 volt appliance. Most RV's only have 110 volt appliances.

The 2nd leg on my 50amp service only runs the 2nd a/c. So when I use the 30 to 50 amp adapter at the parks I lose the 2nd a/c function as the 50amp service only has one hot leg in it while using the adapter.

Also, not true. While one A/C is on one leg and if you have the second A/C, it is on the other leg. The load in the breaker panel is split between each leg of the service. Every other pair of breakers is on alternate legs

 

[TedS]

Scotyb, you are correct in that 220v is delivered to the RV 50-amp connection. There is 220v measured between the two hot legs. The miswire happens if one 120v hot is connected to the RV neutral. That puts 220v on appliances on that circuit.

 

[scottyb]

So from what I reading, they should never come from the same bus. If you ever meter the two hots and only get 120V, you should not use that plug. It can create a dangerous situation if using a lot of amps on each side. Something to do with sync'ing and too many amps going across the neutral at the same time.

 

[scottyb]

Scotyb, you are correct in that 220v is delivered to the RV 50-amp connection. There is 220v measured between the two hot legs. The miswire happens if one 120v hot is connected to the RV neutral. That puts 220v on appliances on that circuit.

I could see this happening more easily with a 30 A plug, if the electrician thought he was wiring 220V. It would be grossly neglegent on a 50A plug. It's certainly convenient to get in a hurry and just plug in to a pedestal w/o checking polarity with a meter, but about 45 seconds could save your bacon.

 

[dave10a]

The 50 amp supply at campgrounds consists of 4 wires. Line 1, line2, neutral and ground. The voltage between line 1 and neutral is 120v and the voltage between line 2 and neutral is 120v. There is a phase difference of 180 degress between line 1 and line 2 that provides 240v. However if line 1 and line 2 are in phase then there is 120v measured between line 1 and line 2.

 

[porthole]

As for the 50amp Rv its more like a 30amp and a 20amp circuit.

Actually it is more like a 50 amp and a 50 amp.

So when I use the 30 to 50 amp adapter at the parks I lose the 2nd a/c function as the 50amp service only has one hot leg in it while using the adapter.

You need a new adapter.

I power my 50amp Rv from my garage. What I ended up doing was installing a 4 way outlet.

What is a 4 way outlet and how do you use that?

I, like many here also plug the RV in at home.

For the most part, the expense of running a 50 amp RV circuit is an unnecessary expense when 30 amp will suffice. Unless, you need to be able to run both AC's at home.
I already had a RV box that I installed from the travel trailer days when I brought the 5th wheel home.
All that was required to use that with the new trailer was new ends on the extension cord that I use, an old marine 30 amp cord that I saved.

The female 50 amp end gets the two hots jumped in the receptacle.

http://www.amazon.com/Camco-55242-30-Amp-Power-Grip/dp/B002OUMU66/ref=pd_bxgy_auto_img_y
http://www.amazon.com/Camco®-PowerG...le-Female/dp/B002ECN0NQ/ref=pd_sim_sbs_auto_4

Prior to changing the trailer's service from the anaconda 50 amp cord to the electric reel, I just used the typical 50 > 30 adapter, which already has the the two hots jumped.

It may seem like I should have just wired a 50amp Rv outlet but I don't have any spare slots to add breakers in the breaker box. I did not want to sacrifice the 110 outlets for something I rarely use.

Although the 50 amp for most is overkill, you shouldn't have to sacrifice any "current" circuits.
Most service panels will accept "twin breakers", not referring to double poles which take two slots and are pinned together, rather two separate breakers that take up one slot. They have numerous names, twin, cheater, tandem etc.

I have one panel that the panel allows all but two twins and a sub panel that allows the bottom four to be swapped out to 4 twins, effectively doubling the the bottom four circuits to 8 circuits.
The label on the inside door has a wiring diagram and will show if "twins" are allowed.

 

[dave10a]

Since my original post was moved to a new topic, I am editting it somewhat. What's the difference between 50A and 220/240v? seems to me they are one and the same. Don't they both deliver 120v from two different legs? I know that a 50A plug meters 240V from one hot to the other. I thought it was just how the power was used once it is delivered to the appliance or trailer. Our trailers only use both legs but only one leg at a time and a 220V appliance uses both legs together. Just curious.

From this normal campground service we can draw 120 or 240 volts. Each
leg is 50 amps @ 120 volts. 50-amp X 120-volt = 6000 watts. But since there are
2 HOT 120-volt legs at 6000 + 6000 = 12,000 watts to use in the RV or 50-amp X
240-volt = 12,000 watts when used as a 240-volt service. Almost ALL 50-amp wired RV's use both sides of the service
separately as 120 volt on each leg. Only a few mostly high-end coaches utilize
the 240-volt from this sameservice.
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

 

[TandT]

Here's the best, most simplified explanation I have found; http://www.myrv.us/electric/Pg/50amp_Service.htm

Trace

 

[5er]

Can I just make a box that receives my 50 amp cord that has both x and y made hot with one leg? I won't overload either side, I just need everything to work at different times.

 

[Silverado23]

There are power adapters available to make both legs hot. One example is a 30amp to 50amp adapter that makes both legs hot but your still limited to 30 amp service. Here is one example http://www.campingworld.com/shopping/item/30-amp-male-to-50-amp-female-adapter-with-handle/57408

 

[mattpopp]

I was under the impression that what will separate the need for a 30 amp service vs a 50 amp service is if you have one or two A/C's. for the example I am using my trailer and my assumption was this is true on all towables.

But my trailer can be completely powered by a simple 30 amp single leg of 120v. Though since I have the 2nd A/C this is why I have a 50amp which includes the 2nd leg of 120v. That 2nd leg only powers the 2nd A/C and nothing else.

With the exception of high end motor homes that actually use a 240v service is this true for everything else? If you have 2 or 3 A/C units you will have a 50 amp service and if you have 1 A/C you will have a 30 amp service?


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[JohnDar]

I don't think that is correct. I only have a single AC, but my Progressive monitor shows current draw on both legs, even when not running the AC. If you have two AC's, one will draw from Line 1 and the other from Line 2, but neither line is dedicated solely to an AC.

 

[danemayer]

As I understand it, the circuit breaker box has one leg feeding a buss bar on top and the other leg feeding a buss bar on the bottom. Some of the circuit breakers use the top buss bar and others the bottom. I think they're supposed to alternate as you go across. See this page for a detailed explanation.

 

[hoefler]

As I understand it, the circuit breaker box has one leg feeding a buss bar on top and the other leg feeding a buss bar on the bottom. Some of the circuit breakers use the top buss bar and others the bottom. I think they're supposed to alternate as you go across. See this page for a detailed explanation.

This is true, in your breaker box, every other pair of breakers is on a different leg. Plug your 50 amp cord into an outlet that has one leg dead, you will see that half of the coach is dead also.