I have a strange issue going on with the power. I have a 50 amp RV with a Progressive Industries EMS and also a Hughes Auto Transformer when needed.As long as the campground does not have many campers (this is on the 30 amp loop, but we have "50 amp" service), we do OK to a point and I have to use the Auto Transformer so that we can run the heat pumps or A/C. We are southwest of Houston, so we get really mixed weather.Now the problem. Without the Auto Transformer, L1 will drop voltage as low as 104 volts which shuts down the EMS. When L1 leg goes low, L2 goes high to about 127 volts with no or a very small load on L2. The EMS drops the trailer off line with L1 low voltage. If I put the Auto Transformer on line, L1 will drop with a 20 amp load and it will boost the voltage on L1 to keep the voltage up. Then L2 will go high and the EMS will take the trailer off line on high voltage on L2.With no or 3 or 4 amp load, both legs will read 121 volts. Add some load and the voltage drops like a rock. I had the park check the pedestal and everything is OK there. I checked all of the connections in the RV and all is tight.The park flooded twice last year and the electrical was under water for 2 or 3 weeks. They closed the park and pulled the guts in all of the panels and replaced them after the water went down.I am at a loss to solve the problem and the park is no help. We are hosting here until the end of March but maybe forced to leave early if they can not get us dependable power. The trailer has a 22 cubic foot residential refrigerator, washer drier, dishwasher and two heat pumps. All appliances are pulling normal amps when at voltage.Any ideas to pass along would be appreciated.Ken

Sounds like it might be an underground problem with the neutral.

Jerry, that is my thinking since they do not know the condition from the flood. They do not have any way to high pot test the wiring. Trying to get the state park to get an electrician out to check it.Ken

TXiceman wrote:this is on the 30 amp loop, but we have "50 amp" serviceWhat does this mean? Is the pedestal 30a? I assume autoformer, EMS and RV are 50 amp.Or as host do you have 50a and the rest are 30?There is only L1 with 30a service so the L1 vs L2 seems confusing unless that is just your RV.Are you using adapters?Otherwise yes whenever voltage climbs it is pointing to a bad neutral.Could check voltages at all boxes in the loop to possibly determine where the issue starts. Or you may end up back at the main panel.

do you have true 50amp serviceor do you mean you have 30+20 ?are you on a 30amp with adapter and where is the autoformer in this circuit30a ped > autoformer > EMS is the correct setupyou can not parallel this with a 20amp on the other legtotal imbalance in the circuits will occur

MrWizard wrote:do you have true 50amp serviceor do you mean you have 30+20 ?are you on a 30amp with adapter and where is the autoformer in this circuit30a ped > autoformer > EMS is the correct setupyou can not parallel this with a 20amp on the other legtotal imbalance in the circuits will occurAgree - in a situation like this accuracy is critical as one can't sort out a problem if isn't clearly described and therefore understood. That aside, since the OP is using a Progressive Industries EMS I'd suggest he call them to see if there's anything they can offer to help sort this out.

50 amp electrical issue | Good Sam Community

TXiceman
Explorer II
Feb 10, 2017
It is a 50 amp site with a 50 amp plug only. The two host sites are 50 amp and the rest of the camping loop is 30 amp.

All the trailer connections and connections in the pedestal are tight. The problem has to be prior to the pedestal.

Ken
myredracer
Explorer II
Feb 10, 2017
When voltage goes down, it's usually due to resistance in the feeder wiring to the pedestal. If so, you'd expect voltage to drop in both 120 volt legs (with same amount of load). What is the line to line voltage measuring? If only one leg is dropping, perhaps you have a poor connection at the shore power to pedestal, maybe dirty plug blades, receptacle in poor shape or bad connection inside the pedestal? But that wouldn't explain voltage rise on one leg. I would suspect a bad neutral connection somewhere. It would be interesting to see what happens if you swapped the hot-hot connections in your RV's panel - if a neutral issue, I would expect a similar rise/drop on the 120 volt legs. The pedestal (by code) should have a 20 amp recept. Maybe check that. If on a loop feeder with other 30 ampers on it, perhaps check voltage there also?

Don't know if this is of help or not.

Getting down to 104 volts is not good.
wolfe10
Explorer
Feb 10, 2017
As several have posted, if one hot's voltage goes up and the other goes down, an open or compromised neutral is the suspect.

The neutral serves as the "reference point" for voltage. Without it, voltage on 50 amp service (i.e. two hots) can range from extremely low to extremely high.
SoundGuy
Explorer
Feb 10, 2017
TXiceman wrote:
It is a 50 amp site with a 50 amp plug only. The two host sites are 50 amp and the rest of the camping loop is 30 amp.

All the trailer connections and connections in the pedestal are tight. The problem has to be prior to the pedestal.

Although you said you have a Progressive Industries EMS you haven't told us which version so I'll take a guess that it's a hard wire EMS-HW50C 'cause if it were a portable version EMS-PT50C the obvious solution would be to forget the rig entirely for the moment and plug the EMS directly into the campsite service to see what you have. That would clearly indicate whether this is a site service issue and not related to your particular rig. Even though I'm running a hard wire EMS-HW30C I wired mine into my trailer using standard 30 amp connectors so in a situation like yours I too could remove it from the trailer in seconds and use it at the post to see what I had. Might be something you'd want to consider for the future. ;)
wa8yxm
Explorer III
Feb 10, 2017
Ok let me do the technical bit, As I said I HAVE SEEN THIS in personal life.
The power is supplied by a 240 volt center tapped transformer.. 120-0-120 or 240 volts across the entire winding.

Now, let's say you have your A/Cs on, and lets, just for chatting sake say the FRONT A/C is on L-1 and the rear on L-2 Other loads are either also balanced or off.. Current flows between L-1 and L-2.. since the two legs are evenly balanced NO CURRENT AT ALL flows in the neutral. Voltages remain 120-0-120.

Now let's assume one of the A/C's shuts off,,, or if it was off the compressor starts. Suddenly that leg is carrying a lot less/more current.

Now the neutral carries the DIFFERENCE between L-1 and L-2 and you basically do not notice much in the way of voltage changes.

Next we do the same thing but with an OPEN neutral.. Now the Neutral can not carry current.

Thus the apparent "Tap" moves.. ONE leg goes UP in voltage, while the other goes down, the total L-1 to L-2 does not change, but the "Zero point" moves so instead of 120-120 you may well have 150-90 or the other way around. NOT A GOOD THING.

Blew a bunch of light bulbs in my house, and reset the coputer (on the low side) till I got 'em out to look at it.. I had two problems.. (Safety ground was not that great either) They fixed the ground and that tamed it.. Then they fixed the neutral and that eliminated it.
Gene_Ginny
Explorer
Feb 11, 2017
TXiceman wrote:
... Without the Auto Transformer, L1 will drop voltage as low as 104 volts which shuts down the EMS. When L1 leg goes low, L2 goes high to about 127 volts with no or a very small load on L2. ...
Open or high resistance neutral.

See above post by wa8yxm
time2roll
Nomad
Feb 11, 2017
TXiceman wrote:
It is a 50 amp site with a 50 amp plug only. The two host sites are 50 amp and the rest of the camping loop is 30 amp.

All the trailer connections and connections in the pedestal are tight. The problem has to be prior to the pedestal.

Ken
Tight may not matter if there is corrosion. Need to measure voltage down the line next time you have a cut in power.

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