Hooking up second AC with 50 amp service

Skipg wrote:
Should the second AC unit be wired on the same line as the first AC unit or on line 2.

Opposite leg as the other A/C. Is your RV pre-wired for a second A/C?
Generally an RV that is set up for 50 amp would be pre-wired for a second A/C if it doesn't already have dual A/C units.

It's pretty easy to install a rooftop A/C unit as seen in this video.
The hard part is getting it up on the roof

The 2nd A/C is usually connected to the other hot leg. But it all comes down to how the rig is currently wired. The loading on the two hot legs should be fairly closely balanced. If, for example, the 1 A/C is on hot leg 1; and the water heater, converter, microwave, fireplace, bathroom outlet where a hair dryer would likely be plugged in are on hot leg 2, then it would be better to connect the 2nd A/C also to hot leg 1. Two A/Cs would pull less than 30 amps, well within safe loading for a 50 amp breaker.

On the other hand, if hot leg 1 had the A/C, water heater, and converter, then by all means the 2nd A/C should be on hot 2.

Look at your circuit breaker labeling and see (if you can) the current power distribution and then decide where to wire the 2nd A/C.

You want to balance the legs as much as possible. I'd put the ACs on opposite legs. I'd put the electric water heater and the microwave on opposite legs.

The second A/C should be connected on the opposite leg from the first A/C.