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myredracer's avatar
myredracer
Explorer II
Aug 27, 2018

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 on reverse polarity.

One of the pedestals also had a defective breaker and in that case the maintenance guy replaced the complete front on the pedestal with an old one from their "stock" of old ones from another nearby CG. The other CG had just completed a major electrical upgrade so they got all the old pedestals.

This past weekend was an odd one. Their maintenance guy recognized me from the previous weekend trip and didn't even ask me why I thought there was a problem. He installed a brand new 30 amp receptacle and a "new" old breaker that was allegedly in good shape. Every time he turned the breaker on, after about 10 seconds there was a faint puff/buzz sound and power went out in our TT. Breaker handle didn't trip. He pulled things apart 5 or 6 times to check and same thing happened each time. It made no sense and kept doing even after redoing and tightening connections. No evidence of carbon tracking.
I've never heard of that happening before. He said he thought it might have been due to the blades on our 30 amp plug (Marinco) being slightly too short but that makes no sense either. Each time power was lost there was no load from our TT except for the converter and each time it took about the same 10 seconds to lose power. Maybe it was a bad breaker?

Then we plugged our 30 amp cord into the 20 amp recept. with an adapter and it worked fine so we spent the weekend running on 20 amps without issue. The "interesting" part was when the maintenance guy went to put the lower cover back on the pedestal and shorted it to one of the live 150 amp lugs and sent sparks a-flying.

All I can say is I sure am glad we have an EMS. Open grounds and reverse polarity are potentially dangerous and even lethal. If you haven't got one, go order one today because you just never know...

FWIW, CGs are something else when it comes to electrical. I've seen so many pedestals and panels in CGs that are in frightening condition and even some exposed wires that should even be condemned in some cases. Then you've got non-licensed untrained people doing electrical work that just don't know what they're doing.
  • 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.
  • An EMS also monitors the voltage level and will shut off if it either goes too high or too low.

    In a packed campground, if everybody's air conditioners are running full blast, it's not unusual to see the voltage drop to below 105 volts. This can damage equipment, as can voltages above 128 volts, which is not high enough for a surge guard to notice and deal with.

    High voltages are much rarer than low voltages, but can happen under some circumstances. I once measured 142 volts on an outlet powering some equipment I was trying to troubleshoot on my job, before I retired.
  • 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?
  • it saved your RV

    I think i would have used a different subject line

    "three weekends in a row, EMS saved my RV"
  • X2.

    I will absolutely not plug in anywhere without my PT50X inline first. And this includes my home base where I have had two high voltage issues over the years - both power company related.