[JRTJH]

If the last couple of posts are correct, then anyone (ALL OF US) with 30 amp EMS and ALL OF US with 50 amp EMS systems who have a 15 amp circuit breaker on an "outlet line" in our trailer, have a 20 amp breaker for the air conditioner or have a 15 amp GFI circuit in our trailer wouldn't have protection "INSIDE" our units, only the 6KW or 3.6KW part would be protected.

In actuality, if there is a "surge" it will typically be a lightening strike or a "massive voltage" (well over 1000 volts) and the EMS (whether a dual line 50 amp device or a single line 30 amp device) would shut down power. If there is over the voltage limit or under the voltage limit (typically they monitor for voltage from 105-130 VAC) then the system will shut down. It doesn't matter if it's line 1 or on line 2, the entire system will shut down. There is no need for circuit protection (at the source/power pole) if there is protection at the circuit level. Think about your home circuit breaker panel. Typically they have a 200 amp "main breaker" and several other breakers ranging from 50 amp/220 for stoves and furnaces, 30 amp/220 for dryers/AC systems, 20 amp/110 for general circuits and some 15 amp/110 for GFI or light duty general circuits. If there's a problem with one line of the 50 amp/220 circuit, there is no "dangerous condition" on any of the "lower amp breaker systems, it doesn't matter whether they are on line 1 or line 2 from the "main breaker".

I'd say that if the 50 amp EMS is connected to a 30 amp power source, it is going to monitor the "LINE IN" for 105-130 VAC/60Hz/50 amps/0 errors. There will be no input on the other line, so the EMS would need to be placed in BYPASS to power the second 30 amp adapter. From that point on, it's the same as plugging the trailer into any power source. The trailer power panel 30 amp breaker will protect the trailer circuits, the power cord (up to the EMS) and the 30 amp (power pole plug) will be protected by a circuit breaker further upstream, probably in the house breaker panel.

I don't see any issue with using the 50 amp EMS on a 30 amp trailer. It will provide the same "surge/lightening" protection no matter how much amperage is being used in the trailer and none of the EMS systems I've ever seen have a "circuit breaker protection built in" so it's irrelevant whether it's monitoring 50 amps or 30 amps, all it does is give a LED reading of how much is being consumed. ALL of the circuit breaker protection is provided by the power center INSIDE the trailer, not the EMS.

The "rub" as I see it, is that SOME EMS systems, when in bypass, will not monitor for low voltage conditions, the manufacturer for that type (CAMCO) recommends not using a 30/50/30 multiple adapter setup. The other brand, Progressive, monitors for low voltage while in bypass, so that brand will work with a multiple adapter setup.