I have a 2005 Workhorse chassis, 8.1 gas 38 ft Sun Voyager. I have two roof mounted AC units one in the bed room and one, in the front area. When both are ON, the one in the front area sometimes makes a rumbling noise like it does not want to stay running after it has been trying to cool for some hours. I am using a step down adapter (Like this) from my inlet to get 30A service with my old 30A cord. (I don’t want to buy a new cord as they are $$$)
So is it OK to just run both A/C units on a 30 Amp step down shore cord to run the AC units?
If you have a 50Amp coach, and you are trying to run both air conditioners on a 30A cord, chances are you are close to maxing out the power you are drawing! From what it sounds like, you are not getting the power you need, and the units are straining. When you use a 50 to 30 amp adapter, you are using a 30 amp single 110volt wire, then splitting into the equivalent of two 15 amp circuits. The two units probably will slave to work, and this causes overheating!
Can I run 2 A/C Units on the 30A Cord?
No question, two A/C’s on a 30 amp circuit is very marginal. If both happen to cycle on at the same time, I suspect it would pop the breaker, particularly if any other 120 VAC items are on such as a charger. I would not do it! In addition to using too many amps, at high amp draws, voltage drops, will increase amp load from the compressor(s). A low voltage will shorten the life of the A/C.
Get yourself a 50A Cord…
You have a 50A coach, you should be using a 50Amp cord (like these). They can be a little bit pricey, but you are talking about a great deal of protection for your expensive RV. These larger cords are heavier gauge and can handle more AMPs, with less resistance. If you want to learn more about resistance and voltage drop, gauge ect. take a look at our article: Voltage Drop & Power Cords