Supply Voltage

[dktool]

Is 240v / 50a supply the standard for new TT's in the say 24' and larger class or is it still more dependent on "as equipped" ?
Are some still 120/30 ?

 

[SpencerPJ]

I would say it is more dependent on if it needs or is prepped for 2 or more AC units. Just an fyi, they make adapters that will convert a plug this 30 to 50 or 50 to 30, just also keep in mind that it would be a great mistake to convert a 30A pedestal plug into 50A rv plug and use 2 air conditioners at the same time.

 

[Onyrlef]

Ordinarily if it’s equipped with two a/c’s it’s going to be 50A 240V, in some cases a unit with two a/c’s may be 30A 120V with a power management/ load shedding system. If it’s wired for a second a/c it may well be 50A already. However, a 30 A with one 15k btu a/c w/o a special capacitor is not going to let you run the a/c with a blow dryer or the microwave at the same time, regardless what the salesman says.

 

[Kirk]

Is 240v / 50a supply the standard for new TT's in the say 24' and larger class

The simple answer is no, it is not standard. That said there are manufacturers that put 50A service in as standard on some models. In most cases it will depend on the particular model and will be more common in the higher priced models. It is much more common when there are 2 air conditioners but even then is not always standard but may be an option. I don't believe that there is anything that is an industry wide standard but 50A service is usually available in larger and more expensive models.

 

[DonTom]

Is 240v / 50a supply the standard for new TT's in the say 24' and larger class or is it still more dependent on "as equipped" ?

240 VAC is rarely used even with 50-amp service.

It's usually two lines of 120 VAC that are used, 50 amps each, for a total capacity of 100 amps at 120 VAC.

-Don- Reno, NV

 

[OldWEB]

240 VAC is rarely used even with 50-amp service.

It's usually two lines of 120 VAC that are used, 50 amps each, for a total capacity of 100 amps at 120 VAC.

-Don- Reno, NV

Sorry, it has to be 240V for the 50A service. 240V is never(?) used but is required if you expect to load up the two 120V lines to 50A each.
That is, if you have a 120/240V 50A service and load both 120V lines up to 50A each, you will have a total of 0 amps on the neutral. Now if you try that with two 120V lines (no 240V between them), now the neutral will have to carry both currents for a total of 100 amps and the neutral in the RV 50A cable cannot handle that.

EDIT: But now that I reread you statement, maybe that is what you were saying also...?! 240 VAC is rarely used...

 

[John From Detroit]

240 VAC is rarely used even with 50-amp service.

It's usually two lines of 120 VAC that are used, 50 amps each, for a total capacity of 100 amps at 120 VAC.

-Don- Reno, NV

No it's not supposed to be what you describe puts 100 amp on the neutral wire
It's supposed to be 240 volt center tap (Divided) so that .. Ideally. the neutral crarries nothing. or nearly nothing.. This is the precise same service (Other than the size (50 amp 100 150 200 more) you have in your house. Not sure what I have in my apartment (no main breaker it's elsewhere) but it's 240 volt.. Divided. But it's truly 240 volt at 50 amp. that's why they call it 50 amp.

Some parks do.. however.. Cheat (or so I'm told and put in the same leg to both sides.. That's a fire hazard.

 

[Onyrlef]

240 VAC is rarely used even with 50-amp service.

It's usually two lines of 120 VAC that are used, 50 amps each, for a total capacity of 100 amps at 120 VAC.

-Don- Reno, NV

Well that's just wrong.

 

[DonTom]

Think in POWER (watts). Then do the math.

It's 12,000 watts either way.

It's 50 amps at 240 VAC which is 12,000 watts.

That means at 120 VAC 50 amps is only 6000 watts.

The other 6,000 watts is in the other 120 VAC line.

Totals to 12,000 watts.

-Don- Fernly, NV (lunch stop on motorcycle ride)

 

[Ray-IN]

Ordinarily if it’s equipped with two a/c’s it’s going to be 50A 240V, in some cases a unit with two a/c’s may be 30A 120V with a power management/ load shedding system. If it’s wired for a second a/c it may well be 50A already. However, a 30 A with one 15k btu a/c w/o a special capacitor is not going to let you run the a/c with a blow dryer or the microwave at the same time, regardless what the salesman says.

I beg to differ. The vast majority of RV's built in the last 25 years are called "50A service". Actually there are 2 legs of incoming 50A service in a 120V configuration inside the RV main panel, for a total of 100A available @ 120VAC. A few high-end MH's actually are wired for 100A service @ 240VAC, they are all-electric MH's.
reference:RV Electric

 

[Ray-IN]

No it's not supposed to be what you describe puts 100 amp on the neutral wire
It's supposed to be 240 volt center tap (Divided) so that .. Ideally. the neutral crarries nothing. or nearly nothing.. This is the precise same service (Other than the size (50 amp 100 150 200 more) you have in your house. Not sure what I have in my apartment (no main breaker it's elsewhere) but it's 240 volt.. Divided. But it's truly 240 volt at 50 amp. that's why they call it 50 amp.

Some parks do.. however.. Cheat (or so I'm told and put in the same leg to both sides.. That's a fire hazard.

Not exactly. The 2 50A legs in the 120VAC main panel configuration requires the neutral to carry some current.
Most 50A RV main panels are designed so installing a 240V breaker is impossible. The 4-wire "50A" RV park pedestal is wired exactly like a 100A 240V 4-prong receptacle.
Don is right.
reference: RV Electric

 

[DonTom]

.. Ideally. the neutral crarries nothing. o

The neutral is called that because it is the center-tap of a 240 VAC home transformer. It does nothing at all on a 240 VAC circuit.

But if you're drawing 5 amps on one side of the 120 VAC then the neutral will also have those same five amps. Or same 25 amps, etc.

The neutral has nothing when you're using the 240 VAC only. It has the full current of either 120 VAC side of it.

Where did you think the return was for the 120 VAC circuits? A simple series circuit must have the same current everywhere. The neutral is the return for the 120 VAC. It does nothing for the 240 VAC circuits as then the opposite 120 VAC leg is the return.

-Don- USA Parkway, Spaks, NV (return motorcycle trip)

 

[Ray-IN]

This is a copy N paste article written by a retired union electrician, written in 2022;
Quote: "

RV 50 Amp Electrical Explained....​

The following is a write up that I did a while back to help explain the RV 50A Electrical system. Many times, there is a discussion about this topic, and consequently, a lot of information that is given is not correct and only serves to further confuse people. So, hopefully this will help and feel free to use it as a reference.


I have to admit....I'm still in shock (no pun intended) at some of the outrageous and totally wrong comments/info that have been given on this topic. The RV electrical systems have been engineered by professional folks, following an established method of electrical distribution that is not subject to your opinion or what you think on how it "should" work, it's based on how it DOES work. So in this case, opinion is totally irrelevant.....and FACT is the determining method of RV electrical systems. The following is a brief explanation of RV 50A Electrical Service….

And the facts are this! A 50A RV electrical system will be comprised of two hot legs, created by what is known as a Split Phase system, and thought of as L1 and L2, a neutral wire, and a ground wire. The two hot legs will be 180 degrees out of phase with each other (and if you don't know what that means, you likely are not going to thoroughly understand how it works) and they WILL IN FACT be able to provide 50 amps of 120VAC PER LEG. In the case of a 50A RV Electrical system, it is basically the exact same as the electrical distribution system INTO your house or home. The difference between the two (RV and your house) is in the electrical distribution panel....a.k.a. the breaker panel. Up to that point (disregarding that fact that your house will use a ground rod at the service entrance and your RV has a continuous ground wire from the pedestal to your RV) the two are exactly alike. Distribution of that power is where the difference is...not the power source itself.

The RV breaker panel is made so that the 50A Main breaker is located in the center of the panel and the associated bus work for each hot leg goes in opposite directions, so it is impossible to have a 240VAC circuit Safely and within Code specs, any place other than the Main breaker itself. In regard to the 50A Main breaker....the LEFT (or top) most half of that breaker feeds 120VAC (with respect to neutral) only to the LEFT (or top) side of the panel for the purpose of being able to install single pole breakers into the available spaces on the LEFT (or top) side of the panel. The RIGHT (or bottom) most half of the 50A Main breaker feeds the bus on the RIGHT (or bottom) side of the panel, providing 120VAC (with respect to the neutral wire) to all of the available slots on the RIGHT (or bottom) side of the panel. The left (or top) side of the panel can be thought of as Phase A...or L1.....and the right (or bottom) side of the panel would then be Phase B... or L2....and MOST IMPORTANTLY....L1 and L2 are electrically 180 degrees OUT OF PHASE with each other. The fact that the two hot legs are 180 degrees out of phase with each other, is what allows the neutral wire to NEVER have to carry any more than 50 amps of current.....even if each leg is pulling the maximum amount of current available to each leg.....50 amps each. So Yes, there is 240VAC coming into the trailer 50A panel, just like there is 240VAC coming into your house. But again, the house breaker panel and the RV breaker panel are configured differently and the result is that you do NOT have 240VAC available for circuits in the RV panel….because of the separation of the two buss bars in opposite directions.

It's really pretty simple if you have been trained and or have knowledge of how a split phase electrical distribution system works.....if you don't, it might be a bit troublesome and cause you to make statements that may not be true at all. Sorry for the long-winded post, but hopefully it may help clear up some of the mis-statements made in this ongoing topic. "

 

[DonTom]

A few high-end MH's actually are wired for 100A service @ 240VAC, t

I think you mean 50 amps at 240 VAC. That is 12,000 watts already.

-Don- Sparks, NV

 

[Ray-IN]

Good catch! I was adding and got carried away. In actuality it is a total of 100A@ 240VAC.(2 50A legs@120VAC each-but that would be an ideal situation) I remember in approx. 2005 I was talking with the owner of an RV park and he was bemoaning the prospect of having to rewire his park for 100A service, for as yet un-built 50A RV's. I think I remember him saying the projected cost was going to be $8,000 per site.
edit; my house has 100A 240VAC electric service and is quite limited for the use of 240V electric appliances, of which I have 3; clothes dryer, kitchen cooktop, and oven, each on a 30A double breaker.

 

[DonTom]

In actuality it is a total of 100A@ 240VAC

You made the same mistake again. That would be 24,000 watts. A 14-50R is only good for 50-amps/240 VAC. The amp rating is what the "50" means in 14-50R or 14-50P.

It's a total of 50-amps at 240 VAC (240V times 50 amps=12,000 watts).

It's a total of 100 amps at 120 VAC. 120 VAC times 50 amps=6,000 watts. Twice (two lines, each hot in respect to neutral) for the same 12,000 watts. But that is still only 50-amps on each 120 VAC connection.

You're not going to lose or gain any power (watts) capacity either way. But if your total voltages will be half, it means you can double the TOTAL current draw to get the exact same wattage capacity at half the voltage.

So the one thing that stays the same in all of this is the 50-amps. 50 amps times one at two 240 VAC. Or 50-amps times two lines at 120 VAC. Total wattage capacity is also the same in each.

All three have a 50-amp limit, but at 120 VAC you have that 50-amp limit twice, 50-amp capacity on each line.

-Don- Reno, NV

 

[DonTom]

my house has 100A 240VAC

A house can be wired for more than that, but the 14-50R at RV parks are only rated for 50 amps at 240 VAC. If an RV park is going to change to 100-amps at 240 VAC, what will be used for the outlets?

And what will the RV plugs be?

-Don- Reno, NV

 

[dktool]

Post #13 is exactly what I would expect in a 50A supply RV

 

[DonTom]

Post #13 is exactly what I would expect in a 50A supply RV

Yep. The main part we were discussing here was:

"WILL IN FACT be able to provide 50 amps of 120VAC PER LEG."

Two legs of 120 VAC=Limited to 50-amps per leg, but 100 amps total.

So the total difference between a 30-amp RV and a 50-amp RV is a difference of 70-amps in total capacity. A much bigger difference than perhaps most realize.

The 30-amp outlets are a single phase of 120 VAC, unlike the 50-amp which are both phases.

So at a 50-amp RV outlet, you can get 240 VAC or 120 VAC twice (or even use all three at once, if done correctly).

But RV's normally only use the two 120 VAC lines from the 240 VAC 14-50R at the RV park. Each line to neutral. No need for the neutral is you're only using the 240 VAC. But not many RVs have any use for 240 VAC.

And I have used the 240 VAC at an RV park--I disconnected my RV and had the 240 VAC go to my chargers for my electric motorcycle. I didn't even put in the lug for the neutral in my 240 VAC charger plug.

-Don- Reno, NV

 

[John From Detroit]

Not exactly. The 2 50A legs in the 120VAC main panel configuration requires the neutral to carry some current.
Most 50A RV main panels are designed so installing a 240V breaker is impossible. The 4-wire "50A" RV park pedestal is wired exactly like a 100A 240V 4-prong receptacle.
Don is right.
reference: RV Electric

I said the neutral carries NONE or Nearly NONE So yes I was talkign EXACTLY
Here is how it works and why. I'd hoped to avoid this post.

Let's say the only thing in the RV is a pair of Air Conditioners. Everythign else is off. Both Ac's are drawing 13 amp precisely.. One on each leg.. Let's say that due to the length of the run from the transformer to the RV the total voltage drop is 1 volt.. 240 volts 120 volts either side of neutral comes out the transformer. 119 volts is now delivered to each A/C and no current on the neutral Zero. Zip. Nada, Perfectly balanced.. NOTE this is nearly NEVER the case.. WHY Well the Converter is drawing a but of power and it's on one leg.. So that current WILL be carried on the neutral.

Let's shut off one of the Air Conditioners.. Now we have one volt drop TO the RV and one Back from the RV to the transformer via the neutral line since it is not carrying 13 amps... the voltage to that single AC is not 19.. but 118 This is why your house, be it mobile or fixed. is wired for 240 volts divided by a neutral 120 either side of neutral.

Of course in real life the neutral Will carry current. but only the difference between L1 and L2 and occasionally that gets to be real real low.

Had a high resistance Neutral at home once.. Was amazing to watch a pair of voltmeters when a big 120 volt device kicked in... Cost me a few light bulbs before I called the power company and they fixed it.