50A additional Shore power to 30A Southwind.

[KSagal]

I started a thread over a year ago about adding a 50A shore power line to my 88 Southwind.

First, a couple details. I have an 88 Fleetwood Southwind with a 30A shore power cable, and a 50A Onan Generator.

I know this is because back in 88 when my motor home was built, campgrounds did not have 50A service available.

It also means that when plugged into the shore power, I could use only one of the air conditioners in the roof, but when on gen power, I could use both ac units. On hot days, I need both ACs to work.

Simply put, I have a 30A motor home. 30A power from shore, 30A transfer switch, and the whole unit works fine on 30A, except that I can only use one AC.

Now, the way the genset works, is it feeds 30A into the transfer switch, and an additional 20A that bypasses the transfer switch to the 2nd air conditioner. (There is a switching mechanism in the cabin that allows me to use either, but only one, air conditioner when on the 30A land line)

So, all I did was open all the leads in one of the junction boxes in my wire locker, that had all the power wires from the Genset where they joined with the wires into the motor home, and more specifically, the transfer switch and the bypass circuit.

I simply took off the wire nuts, and installed a wire and a male and female connectors in line. To make the motor home act as it has for the last 30 years, I simply plug my new 50A shore power cord into my new 50A socket inside my wire locker. (At this point, I can start the generator, and use both air conditioners, or whatever)

But, I can also unplug the 50A from my new socket, and plug it into the campground outlet, and do the same thing.

When I do this, the input is the same to the motor home, so it does not know, nor does it care, if the 50A is coming from the generator or the campground pedestal.

Once this thread is on line, I will be adding some more details. One Warning: I am an electromechanical engineer by trade so some of the things I have done I take for granted. I DO NOT SUGGEST YOU DO THIS, and think if you want to try to duplicate my wiring, you should have a competent electrician or professional do the work. If you do what I did, and your motor home is slightly different than mine, or you make a minor mistake, people can get hurt, you can have a major short, or even worse. Please do not do this, especially if this is your only source of info...

[KSagal]

This is the wire diagram that resembled my motorhome, and I did a crude change that shows where I inserted the cable and outlet.



I understand that my drawing is crude but you should be able to get the idea.

If you look carefully at the wire diagram between where I added my wires, it says 'cut' but I simply did this at the junction box where the wires from the generator were wire nutted into the motor home wires. All I did was open the wire nuts, and add one set to one side, and another set to the other side. So, I never actually cut a single wire.



This image simply shows the new 50A cord plugged into the 50A outlet that I added to the top of my wire locker.

With the plug in, the wiring is exactly as it was before I meddled in, but has 50 feet more wiring between generator and transfer switch.

But, if I unplug this cable from the wire locker roof, and plug it into the camp pedestal, then the transfer switch sees the voltage on wires coming from the generator, so it does what it always did.

The transfer switch is looking for voltage on inputs. It does not care or know where that power is coming from.


This is just a little embarrassing, but I have not yet installed a 50A outlet at my home. I keep my motor home in a pole barn I built for it, and still have the 30A line I installed at that time, and have not bothered to upgrade it yet.


There is one slight difference.

If I am plugged into shore power with the 30A, and I start the generator, the transfer switch will automatically deaden the 30 amp power line so I do not need to unplug from the pedestal. It is automatic, and I do not need to do anything else.

If I am plugged into the shore power with the 50A, and I start the generator, the transfer switch will deaden the 30A shore line (which is good that the male end is dead, and there is no voltage on the exposed posts) but it will not use generator power, as it will simply power the female outlet in the wire locker. (in other words, there is no reason at all to even start the generator when the 50A is plugged into a working pedestal)

So, if plugged into 30A, and the camp has a power outage, I can go to my dash board and push one button and get the gen to start. I do nothing else.

IF I am plugged into 50A, and the camp has a power outage, I need to go outside and unplug the 50A from the pedestal and plug it into the outlet I installed, then go to the dash and push the button.

A small price to pay (which I have never had to do) to get both ac units working, and without burning my own gasoline.

I have seen none or very little cost in camping at a site with 30A or 50A at a campground. When paying $40 or 50 a night, and plugged in, it used to drive me crazy to also need to start the genset to cool down the motor home. I like it better to use the camp power, which I already paid for....

[F239141]

You can also add a 20 amp shore line in to the feed for the rear air. What you will need to do is install a junction box, take and cut the wires off the generator and install a female plug, then on the wires going to the AC install a male plug.

When at a campground you plug a 20amp shore line into the ac end and then into the 20amp plug on the campground box.

When using the genny you plug it into the genny plug.

Otherwise you will need a transfer switch of some sort on the 2nd ac line .

You can make an adapter that will take the 50 amp park plug and split it into a 30 amp and 20 amp for campgrounds with only 50 amp plugs.

[Buffaloman]

Thanks this looks like good info. We also like the motor home cool. My brother is a elections by trade Ill have to get him to help do this.

[Mr_D]

A true 50 amp generator is 12,000 watts (2 X 50 X 120 = 12,000) as is the service pedestal, very doubtful you have that.

First, a couple details. I have an 88 Fleetwood Southwind with a 30A shore power cable, and a 50A Onan Generator.

[Arizona]

Looks like a good solution. I had a similar problem years ago and put in a contactor in line with the second a/c with the 120 control coil and the a/c plugged into the pedestal with an extension cord. Moho worked as normal until you plugged in extension cord.

[KSagal]

Several folks suggested a 2nd cord for the 2nd air conditioner.

My issue was that while the 30 amp land line would only feed one AC unit, it was not always the same one. I had a set of switches in the lounge, in a cabinet, 6 feet from the front AC, 20+ feet from the rear one.

Those switches looked like standard wall light switches, but had 3 positions, up, down, and center. With the switches in one position and the land line plugged in, a certain AC had power. Move the switches, the other would have power.

When the genny was running, those same switches and same positions had different assignments. I could with hold power from an AC or let them both run.

I did not want to disturb this wiring, which is why I tapped in near the genny, so that I did not interfere with any of the MH wiring, as it still worked well, and did not need my meddling.

[KSagal]

Originally Posted by Mr_D

A true 50 amp generator is 12,000 watts (2 X 50 X 120 = 12,000) as is the service pedestal, very doubtful you have that.

I am sorry my motor home does not meet with your approval, or alleviate your doubts.

I previously included a diagram that appropriately represents what I have in my motor home.

[mohamer]

Carl,
Thank you for posting, my MH is wired like yours. I think I will work on doing something like your project. I remember a MH my Dad had that was set up so that if you wanted to use the generator you had to plug the power cord into the generator outlet. That was before the manufacturers started putting transfer switches in a lot of MHs.