50 amp electrical issue

[TXiceman]

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

[time2roll]

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.

[Gene_Ginny]

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

[wa8yxm]

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.

[SoundGuy]

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. 😉

[wolfe10]

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.

[myredracer]

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.

[TXiceman]

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

[wa8yxm]

Have seen this with my very own voltmeters, In my Sticks and Bricks

OPEN or partially open NEUTRAL (Sticks and bricks was partially).

Suspects include the park and everything between the park and your EMS including all plugs, cords, and connections, but I suspect the park the most.

IF you have a plug in volt meter, Plug into the 20 amp outlet on the park box and watch the voltage there, if it's a park problem it will go low/high along with your interior voltage.

[Chris_Bryant]

And test the other 30 amp sites- if they act the same (sag and over volt), the problem is pretty serious, likely due to the flood. If it's just the 50 amp outlet, it's in that outlet or close.

[fairway2002]

Hello

Are all your test points inside RV? Test at pedestal. Same readings you know its the park power.

[Mandalay_Parr]

TXiceman wrote:
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

That's a good idea to have electrician come out. Make sure he understands fully what is going on.
Testing the pedestal voltage under load is the best way.
Another is to completely disconnect that branch circuit from the main panel then OHM out all wires involved. Hi pot would be best. Should be no continuity between the 4 conductors.
keep us posted.
Good thing you had EMS. I use the same one too.
My neighbor had some serious damage once. He didn't have one.

Jerry

Ps. I've troubleshot and repaired underground problems in the past.
You never know what you might find.

[westend]

What the OP describes is an imbalance between the two legs of service that only happens when using the Hughes unit. The statement that he is unable to run an A/C or heat pump without the transformer is more telling than anything else since that should be easily accomplished with good service to the pedestal.

I wouldn't want to sit connected to a service that sagged to 104V under a typical oad. Your EMS is saving your bacon with that situation. My guess is that the campground has a problem with their campground "grid" and I wouldn't be looking for a quick solution to the problem. Sorry for the negative post on my part but you have all the good gear to camp with adequate or typical electric service and that isn't' being provided.

[SoundGuy]

MrWizard wrote:
do you have true 50amp service

or do you mean you have 30+20 ?

are you on a 30amp with adapter and where is the autoformer in this circuit

30a ped > autoformer > EMS is the correct setup

you can not parallel this with a 20amp on the other leg
total imbalance in the circuits will occur

Agree - 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.

[MrWizard]

do you have true 50amp service

or do you mean you have 30+20 ?

are you on a 30amp with adapter and where is the autoformer in this circuit

30a ped > autoformer > EMS is the correct setup

you can not parallel this with a 20amp on the other leg
total imbalance in the circuits will occur