I have had my Progressive HW-50C EMS installed in my Bighorn since 2014, been fulltiming since 2015. I am a retired electronics technician of 40+ years experience. Here is info about my setup and how I use it.
I bought my EMS from Progressive at the Quartzite RV tent. I installed it in my storage compartment utilities crawlspace next to the transfer switch. I installed it before the transfer switch so it would not get power produced by my pure sine wave inverter system. I screwed it to the floor.
I noted that the box consists of MOV impulse absorbers, a computer logic circuit board, a large 3 pole electrical contactor, and interconnections. Based on the fact of the contactor being present, and my work experience with large current relays arcing, pitting, and failing at the contacts due to switching heavy current loads, I resolved to put the minimum amount of loading on this hard to access contactor. To that end I turn off the main INSIDE circuit breakers BEFORE disconnecting from shorepower when leaving a campsite, and only turn on those inside breakers ON AFTER connecting to shorepower and turning the campsite breaker ON. This causes the EMS contactor to switch with 0 current load, and the only current load switching to be done is at the inside main breakers. This saves the hard to access, hard to get new parts, EMS contactor relay. I got a spare set of mains breakers at the local Home Depot, and the breaker box is easy to get to for repair exchange of the breakers.
A couple of years ago, in very hot weather, while staying at a park with 30 amp (110 volt) shorepower, the EMS clicked off and was reading "255" volts on both phase readouts of the box. I verified that the supplied power was OK with my DVM, and knew that "255" was indicative of a logic circuit malfunction in the EMS. I contacted Progressive, told them of my electronics experience, and they sent me a new logic board. I found that the old logic board had a swollen capacitor near the bottom of the board. I also felt that although the EMS enclosure was very well sealed against moisture intrusion, this very sealing prevented any cooling air for the logic board components. Since I felt secure about the box not getting wet in the depths of the compartment (I had already replaced the plastic black tank cleaner atmospheric check valve), I decided to drill a row of small holes in the casing above and below the PC board. This should allow some convection air cooling while minimizing moisture exposure. I also mounted the case above the solid floor with some spacer nuts to allow airflow.
Lately I have been getting ERROR 10 (MOVs inop) off and on. Progressive sent me a new MOV pack I have to install. A little more worrisome is the fact that about once a month I get a power shutdown, with immediate reset (after the 30 second delay) with a previous ERROR 7 readout. Since ERROR 7 is a detection of "LINE FREQUENCY HIGH", and I have been in different RV parks on shorepower when these happened, and that a true power frequency shift on a powergrid intertied power source would cause MASSIVE damage to the intertied powergrid infrastructure, I am guessing this alarm by the EMS has to be false, and I probably need yet another logic PC board for the EMS. Lucky there is a lifetime warranty for the system. Right now, this problem is just a nuisance, with the biggest irritation is just how long it takes the satellite TV system to get reset. Also, this IS causing EMS contactor power load arcs.
When I crawl in to replace the MOV board, I plan to also file the contactor relay contacts, and spray them with Cramolyn DeOxIt contact restorer/cleaner.