MrWizard wrote:
With the fan and compressor timers built into the A/C of most new RVs
The only loads will be the converter water heater etc..
A/C compressor instant load is a much LESS likely problem, than it used to be
A manual transfer , is the safest most reliable mode
The converter and (especially) water heater are a significant load for a generator to have to start up with. An automatic transfer switch lets the generator start up with no load (well, except for a relay coil or two in the transfer switch itself).
You could accomplish the same thing by turning off the main breaker before starting the generator on a rig with a manual transfer setup, or by plugging the power cord into the generator socket after the generator starts up, but I suspect relatively few people do that all the time. Similarly, you also would accomplish the same thing by wiring an EMS in with its time delay. But absent any of these, the automatic transfer switch is significantly gentler on the generator when it's starting up.