3 weekends in a row, EMS tripped each time
Installed a PI EMS unit (30 amps) in our 2014 TT when we bought it. Last time it tripped was 3 seasons ago. On each of the 3 last weekend outings the EMS has tripped! Twice on open ground and once ...
Forum Discussion
BFL13 wrote:
Would a "surge guard" have saved the RV in those same situations? mine (Model 44740RV RV30)also has "Shockshield", which is a sort of GFCI near as I can tell from the (vague) instructions.
What does an EMS do that a surge guard doesn't?
You're correct that Shockshield is a GFCI; there's also a couple of MOVs providing (rather limited) voltage surge protection. There are various models of SurgeGuard units which provide varying additional protections, and the higher end ones would cover the same sorts of things that these other EMS units provide.
Briefly, they disconnect when the input voltage is too high or too low, or when they detect a miswired outlet (swapped hot and neutral or unbonded ground). Most if not all PI EMS units do not provide ground fault protection for the RV. They do also have a few MOVs for (again rather limited) voltage surge protection. I think the PI EMS units also disconnect for wildly incorrect line frequency, but the chances of encountering that are pretty much nonexistent (their allowed range is something like +/- 10 Hz, while the electric grid is regulated much much more closely--around +/- 1 Hz short term and much more accurately over the course of days or weeks so electric clocks stay correct). Finally, these units usually have a turn on delay mainly to prevent restarting an air conditioner against a full pressure head in the event of a brief power interruption.
The low voltage, high voltage, and miswired socket protections are probably the most valuable, in my opinion. High voltage generally is a result of miswiring somewhere, commonly a poor or broken neutral connection at some point.
