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Old 06-22-2013, 09:34 AM   #1
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Apache Junction , Arizona
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50 Amp factory installed power service

I have a question for those folks with Airstream factory installed dual AC units and 50 amp service. The supplied 50 amp power cord is designed for a matching 50 amp power outlet. The information I have read is that the wire size (should be #6 copper for 50 amps) in the supplied cord is for 120VAC service even though there are four conductors and pins.

I searched the major portable generator brands 5000 to 6500 watt generators and none offered a 50 amp power outlet. They usually had a twist lock 30 Amp at 120Vac and a 30 Amp at 120/240Vac power outlet.

The 2013 Airstream parts book shows a 50 Amp Square D box that could support 8 wide breakers or 16 narrow breakers with a service rating of 100 Amps. The three connectors are for two 120 VAC legs and a neutral. I imagine there is a separate grounding bar as well.

The four wire power cord implies two 120vac legs, a neutral and a grounding conductor. I could understand the concept of bringing in two 120VAC lines and just putting the second AC on one leg by itself.

Then when plugged into a 30 amp 120VAC service, the second AC would not attempt to start as it lacks power. Simple, except the option to run either AC would be precluded. Also, if the park power outlet actually is wired with 50 amps on one leg, there would be no way to get power to the second AC.

The other option would be a voltage sensing switch that would send two 120vac input lines independently to the lugs of the power panel and if only a single line 120Vac power was sensed, it would cross connect and send the one leg power to both lugs in the panel.

Returning to the generator outlets I found. A 30 amp 120/240 twist lock would allow 30 amps on each 120VAC leg to the trailer. Since single AC trailers have 30 amp service, one leg would function as normal and the other leg could feed AC #2. There could be an imbalance on the neutral wire as the equipment load might not be evenly distributed in the panel.

Can anyone shed some light on the wiring in the 50 amp service coaches?

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2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels
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Old 06-22-2013, 09:40 AM   #2
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There is no generator with 50 amp output as you have discovered. There is talk of pairing generators. You plug your 50 amp umbilical cord into the 30 amp generator output with an adapter. Don't try to run both air units.

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Old 06-22-2013, 10:38 AM   #3
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I previously had a 34-ft LY diesel pusher. It had a 6500-Watt LP-powered generator that had a 30-amp and a 20-amp output. (Nominally 30-amp at 240-volts) This setup powered both 13,500 BTU air-conditioners simultaneously - the rear one on the 20-amp circuit. The rig also came with 2 ATS (automatic transfer switches). One of the mods we made was to change the 30-amp shore line to a "50-amp" shore line, which meant going from a 120-volt 30-amp 3-wire cable to a 240-volt 30-amp 4-wire cable. We had to combine the two ATS switches into one (the original circuit had the neutrals being switched - advice received from CSA was that this was not necessary). The ATS switches have a built-in 60-second time delay relay to allow the generator to reach full potential before switching the load over to it.
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Old 06-22-2013, 11:25 AM   #4
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Originally Posted by m.hony View Post
There is no generator with 50 amp output as you have discovered. There is talk of pairing generators. You plug your 50 amp umbilical cord into the 30 amp generator output with an adapter. Don't try to run both air units.
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