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Old 06-27-2019, 10:20 PM   #1
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Join Date: Dec 2018
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Talking 1997 National Dolphin 535 dual air conditioners

I have front and back Dometic air conditioners and my 97 Dolphin that runs off of 30 amp shore power. I can't get them both to run at the same time on shore power. They work fine together on the generator. On shore power the front one will cycle on and off while the rear a/c continues to run. I have read where other people with this year and model have been able to run both of theirs on shore power so I am looking for suggestions on how I might be able to do the same. Here in Central Texas with the heat and humidity I need both of them to cool the coach. I suspect that it has something to do with the Intellitec Energy Management System model 120 however I have not been able to find any description of operation, diagrams, or manuals to help me determine if that could be failing or if it is operating normally.
If I can only get one to work continuously then I would prefer that it be th he front one and the back cycle on and off.

Any comments or suggestions would be greatly appreciated.
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Old 06-27-2019, 10:45 PM   #2
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National RV Owners Club
Freightliner Owners Club
Join Date: Aug 2015
Location: Fayetteville, TX
Posts: 194
Running two units at the same time is pushing the limits of a 30A connection. Each 13,500 btu unit draws about 12.5A (25A for two). That doesn't leave much head room for any other loads like your inverter/charger, lights, etc. If you find a good solid 30A connection you should be able to run both, if virtually nothing else.

However, it's not unusual to have less than 30A service on a 30A RV connection at a campground because circuit breakers de-rate every time they trip. That means it might take a 33A load to trip the first time and 29A by the 10th time, etc. Campers routinely trip 30A services and depending on how old the breaker is you might not even get it to hold for a 20 to 25 Amp load. Accordingly, what works at one campsite (two A/C units running) might not work at the next campsite.

When connected to 30A service I turn one of our two A/C units off.
David (AE5DS) & Linda Stall - F452322
1999 Tradewinds 7372 - Freightliner XC - Caterpillar 3126B - Generac IM-72LP
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air, air conditioner, dolphin, national

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