30 to 50 amp conversion

[Honkity Hank]

We would like to convert our 30amp shore power to 50 amp so both A/C units can be run on shore power. I am certain there are different solutions to this, what is involved in doing this (85, 345 by the way).

One question is how the control panel (above the kitchen) gets rewired, if I remember correctly, when on shore power the control panel only lets you select one A/C unit. Can this be rewired to allow both to be selected, or is my memory incorrect on this?

If you have done this please let us know how you did it.

Thanks

Jeff
1985 345

[markdoane]

I have done this, but on a trailer, not a moho. I recommend a kit that CW sells, by Marinco, that includes the 240V/50a inlet, wiring box, and cord end connector.

You can purchase a main lugs panel from Progressive Dynamics that has separate neutral and ground bars. . . http://www.bestconverter.com/view_category.asp?cat=52
. . . or you can buy some other brand.

The important thing is to try to keep the two legs balanced so that the neutral leg doesn't exceed 50 amps. Be aware that you will have TWO - 50 amp legs for a total of 100 amps at 120v.

[cooperhawk]

Have not done it yet, however, when you run the generator both ac's will run so the circuit must be there. I haven't done it yet because there are so few campgrounds with 50 amp hook ups, and if there are, the voltage is usually so low as to not be able to run the ac anyway. I will bet that in a few years though, there will be plenty.

I'll follow this thread to see if someone has done it.

[TomW]

Originally Posted by markdoane

... Be aware that you will have TWO - 50 amp legs for a total of 100 amps at 120v.

It is my impression that a 50 amp service at a campground consists of one leg limited by circuit breaker to 20 amps, and one leg limited to 30 amps. 50 amps total.

Where is "100 amps" coming from?

Tom

[markdoane]

I think that is because some Airstreams were built with a regular 30 amp/120v service, plus a separate 20amp service for running the A/C from a second, independent power source.

The required 240v, 3 wire RV standard is two 50amp legs, total 100amps of 120v.

This doesn't mean that some campgrounds don't cheat and give you the 30a + 20a treatment.

[guy99]

I have used 50 amp service to run both AC's on many occasions. I have copied an old post from another thread to explain how. This isn't a neat as having a single 50 power cord but on the other hand you don't have to deal with a 50 amp cord even when you don't need the extra power.

I didn't install this it was in the coach when I bought it. The coach has a water cooled Honda EV6010 generator. This generator has two output circuits, a 30 amp and a 20 amp. The 30 amp is directly wired through a transfer switch to the coach 'service entrance'. The 20 amp circuit is wired to a female (30 amp RV type) receptacle in the generator compartment. The rear AC is wired through a dedicated circuit breaker to a 30 amp rv type male plug which is plugged into the aforementioned receptacle. So, when the generator is running the rear ac gets power through its edicated circuit. A 50 RV hook up is really a 240 volt circuit with two hot leads an A and a B. The A and B legs cycle out of phase so the the voltage between them is 240 volts. Each leg has a voltage of 120 volts between the leg and the neutral wire.

So, when we are parked and have access to a 50 amp rv plug and I want to run the rear AC I use a special pig-tail which I wired myself. One end is a 4 wire male 50 amp plug, this branches into two 30 amp female plugs. One of the female plugs is wired to the A leg, the neutral, and the ground from the 50 amp plug. The other female plug is wired to the B leg, the neutral, and the ground from the 50 amp plug.

I plug the main coach 30 amp plug to one of the female plugs. I run a 30 amp extension cord from the other female plug to the generator compartment where I unplug the rear AC from the socket from the generator and plug it into the extension cord. This results in the coach being powered by one leg of the 50 amp circuit and the rear ac being powered from the other leg. Since each leg of the 50 amp circuit can supply 50 amps before the circuit breaker blows, you must be sure that you 30 amp breaker is working or you could overload the wiring in the 30 amp cords. I also understand that it is possible if the ground (or neutral?) is bad that you can end up with more than 120 volts on the A or B leg. I am not an electrician so please be sure that whatever you do is safe.

Here is a link to a commercial source for the special pigtail:

http://www.rvupgradestore.com/index....ROD&ProdID=142

[bryanl]

The big difference between 30 Amp RV service and 50 Amp RV service is that the 30 Amp service is single phase 110v, just like a typical household outlet except with a bigger fuse, while the 50 Amp service is split phase 220 volt like used for major appliances. This means a 30 Amp RV service can provide about 3 kW of power with a 50 Amp service can provide 11 kW.

A 30 Amp service provides hot, neutral, and ground connections and inhabits just one side of a typical fuse box with a single circuit breaker.

A 50 Amp service provides a hot, an opposite phase hot (this means it is 220v away from the other hot line), a neutral (110v away from either hot), and a ground and inhabits two sides of a fuse box needing two fuses. This is just like most residential power feeds except those are often 100A or 200A (2 to 4 times as much power).

Going from a 50A service to 30A service means just tapping one side or the other of the 50A and limiting the current (fuse or circuit breaker) to 30A.

Going from 30A to 50A will require changing service boxes to one that will support split phase power feed and upgrading from that box all the way back to the power source for split phase 220v at a higher current level.

Since most RV's set for 50A service do not have 220v appliances, it is possible to 'cheat' and feed single phase (110v) limited power (30A or 3kW) to each phase in parallel (no 220v available).

Normally, with balanced split phase power - that means that the 110V loads for each of the two phases are about the same - the neutral line carries very little current. This is why it is sometimes a smaller wire than the hots. If the phases are paralleled, the neutral carries current equal to the sum of loads on each phase (when split phase it is the difference).

Note that the ground and neutral should only be connected together at the supply source. For a house, this is where the main fuse box is. For a genset powered RV this is at the genset. If the genset is in the RV and otherwise isolated fromt the environment, this safety code rule isn't an issue. An RV service entrance should not bond the neutral and ground.

This is the long way to say what Mark said ;-)

[bryanl]

note, if you get confused about the 220v and 240v, dont' worry, you are in good company. The easiest way to think about this is that 110v service is really 117v service plus or minus 10%. (105 -129v). When this is doubled, it means you are talking a range of 210- 257v.

So 110v for the low side and either 220v or 240v for double that is convenient.

If that isn't good enough, then you can get into the three phase power supplied to neighborhoods, Y and Delta configurations, voltage and phase in various ways of tapping things, split phase vs two phase arguments, and such things. See Single-phase power systems - Chapter 10: POLYPHASE AC CIRCUITS - Volume II - AC http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
for more on this. Fun stuff.

[garry]

This is a picture of a home made 50 amp to 30/20 amp conversion without having to modify the inside RV breaker box.

This unit has a 50 amp male plug that plugs into the campground post.
A circuit breaker box with one 30 amp breaker and one 20 amp breaker installed.
From the 30 amp breaker a 30 amp RV female plug and from the 20 amp breaker a 20 amp standard household type plug. This gives me the protection from overloading the RV.

If you are not familiar with electricty don't attempt to do this yourself, you need two 120vac output's to your RV "NOT" one 220 vac.

Not sure of the cost I only had to buy the breaker box at $18 since I had everything else in the junk box.

[garry]

I left out the 50 amp connection side

L1= 120 vac 50amp to 30 amp breaker
N = N
L2= 120 vac 50 amp to 20 amp breaker

Garry

[TomW]

Originally Posted by markdoane

... This doesn't mean that some campgrounds don't cheat and give you the 30a + 20a treatment.

The odd thing is that I never thought anyone was "cheating", i.e. I thought 30 + 20 was the definition of 50 amp RV service.

Now granted, my Airstream only needs a 30 amp service, and I will admit to not paying rapt attention to the service panel at sites we have stayed at that also had 50 amp service available, but disregarding how the trailer is wired, are most campgrounds wired for "50 + 50"?

My gut feeling is "no" based on what I have taken the time to look at. But I would really like to know what the rest of America generally expects/finds at a campsite.

FWIW, my "corner of the world" is within an 800 mile radius of north AL.

Thanks,
Tom

[bryanl]

Tom, an RV Park wired to code with the proper 50 Amp RV receptical will have two connected 50 Amp circuit breakers across a 220v bus behind it.

If you wander through the electrical department at Lowe's or HD you will see a variety of plugs and receptacles, each for a specific circuit and load configuration. If I understand right, electrical codes require that these be supported by the proper wiring and fusing.

You can see this sometimes in your house. Your kitchen probably has outlets where one of the vertical slots has a cross slot on it. This inidates a circuit rated for 20 amps rather than the usual 15 on a household circuit.

I rather doubt that an RV park with a 50A outlet backed by 20 and 30 amp breakers is going to get past a building inspector these days. But then, I am not in that business so what I have is all theory.

[TomW]

Originally Posted by Leipper

... But then, I am not in that business so what I have is all theory.

Bryan,

I understand the points you have made, and I am not in the business either. My curiosity lays in the application, that is, who is actually finding 100 amp service, or at least breakers rated for that service, at their campsite?

My take is "not many". But why would most people even check if their plug fits the receptacle, and they camp happily?

I am just curious, and am hoping that a few members may have given a second look to their campsite's service panel.

Tom

[guy99]

We have close friends who full time in a big diesel pusher. Based on what he has said and my much more limted experience, the 50 amp plugs found in campgrounds really do have two 50 amp breakers and supply 50 amps to both lines. Sometimes you will get an unacceptable voltage drop if you draw too much current but the breakers (50 amp) don't trip.

[TomW]

I take it your friends are in the California area also?

I guess I should have also asked "... and what area are you finding 100 amp service?"

Thanks,
Tom

[guy99]

Actually, they travel throughout the US, as we have. I haven't noticed a regional pattern. Usually if the site has a 50 amp plug it has 50 amp power. In many cases only a limited number of sites will have 50 amp power. Often these cost a few dollars more. The only time I'll pay more for 50 amps is when it is hot and muggy and I want to be able to run the back AC.

[john hd]

tom etal,

50 vs. 100 amps is confusing if you are talking about single phase loads vs. 2 phase loads.

imagine this, a single phase load of 30 amps runs thru a breaker to the load and returns on the neutral wire. 30 amps each way phase and neutral.

now lets think about a 50 amp load on a 240 volt circuit, 50 amps travels thru a breaker and returns on the other phase wire thru the other breaker NOT the neutral.

a pure 240 load at 50 amps will have zero amps on the neutral wire.

can you pull 100 amps of single phase load thru a 50 amp rv connector? in theory you could, in reality no. (that is what they taught me at lineman school)

so, the manufacturers of rv pedestals will set them up for two 50 amp circuits because they are in fact actually a 240 volt outlet capible of providing 50 amps on each phase in and out, not on the neutral.

you can run 50 amps thru one single phase without tripping the breaker phase to ground.

if it was set up to be one 30 and one 20 amp breaker on 2 different poles you would blow the breaker in the above scenario.

simple? perhaps not!

john

[garry]

To simplify:For 30 amp service:A 30 amp campground pedestal is wired for 120vac with a 30 amp circuit breaker. You plug your RV 3 prong electrical connector into the panel and you have 30 amp 120vac service. If you try to pull more than 30 amps the breaker will trip so you are limited to 30 amps by the breaker.
Inside the 30 amp RV you have a distribution box with a 30 amp main breaker and several 15 or 20 amp breakers that feed different loads in the RV all of which are 120vac. The main breaker in the RV also will protect you from pulling more than 30 amps by tripping.

For 50 amp service:A 50 amp campground pedestal is wired for 240vac with two 50 amp breakers (100 amps). You plug in your RV four prong electrical connector and you are protected by two 50 amp circuit breakers. 50 amps on each leg.

Inside the 50amp RV the distribution panel is wired so the 240vac is divided into two 120vac legs protected by 50 amp breakers. These legs (L1 & L2) feed the 120vac through 15 to 30 amp circuit breakers to power the 120vac appliance loads. You might have a washer/ dryer and 2nd AC on one leg and everything else of the other leg. Each leg is 180 degrees out of phase and 120vac

. Hope this helps.

[guy99]

I used the term campround loosely. I really meant many RV parks have 50 amp power, not govenment operated campgrounds or parks.

[Honkity Hank]

Originally Posted by guy99

I have used 50 amp service to run both AC's on many occasions.

So, when we are parked and have access to a 50 amp rv plug and I want to run the rear AC I use a special pig-tail which I wired myself. One end is a 4 wire male 50 amp plug, this branches into two 30 amp female plugs. One of the female plugs is wired to the A leg, the neutral, and the ground from the 50 amp plug. The other female plug is wired to the B leg, the neutral, and the ground from the 50 amp plug.

I plug the main coach 30 amp plug to one of the female plugs. I run a 30 amp extension cord from the other female plug to the generator compartment where I unplug the rear AC from the socket from the generator and plug it into the extension cord.

This seems like a simple solution but I am concerned about one issue. When on shore power what happens if the selector switch above the kitchen is switched to "rear A/C"? Does that send both legs (and therefore 2 out of phase 120V circuits i.e. 208 volts) to the rear A/C?

Jeff