Low voltage help

[Lori]

Hello! I have a question hopefully someone can help me with. I have a neighbor in the campground and his rig is brand new. DVR suites fifth wheel.

the campground pedestal voltage on both legs reads 117  when he has three acs on and fireplace and lights and microwave( we were testing) he was drawing 42 amps approx. the inside of his rig has a progressive 50 amp hardwired ems. It reads wacky. It said 117 on one leg then 106 on another. Then 109 and 106. The outside pedestal is still reading steady at 117. His rig will power off periodically because of the progressive ems ready the low voltage. What could cause this low voltage reading on the ems, when the campground pedestal is providing the correct voltage? I really do not know much about electricity. Could this be something wired incorrectly in his brand new rig??

[Chad Heiser]

How are you reading the voltage on the pedestal?  It needs to be read under load, not just at rest before you plug the trailer in.  The voltage at rest will almost always read normal.  Then once a load is put on it (3 AC's, fireplace, microwave, etc) the voltage can sag if the overall system is not robust enough to handle it.  As the amperage draw goes up, the voltage will go down if the system isn't capable of handling the load.  This is common in older parks or parks with insufficient electrical infrastructure.  It sounds to me as if the EMS in the DRV is doing exactly what it should be doing, cutting power as the voltage drops on the system as a load is applied.

Now if you are measuring the voltage at the pedestal and getting normal readings at the the same time the EMS is reading low voltage (under load), then that is a problem.

Unless you have an EMS, most times you have no idea of low voltage situations.  Even if you measure voltage at the pedestal when you arrive and check that it is wired properly with a quality meter, you probably will not catch a low voltage situation because the low voltage won't occur until a load is applied to the system.  This is why I recommend everyone use an EMS on a modern RV.

[Lori]

Hello, a voltage meter and it was read with the 50 amp plug plugged in. They pulled it out a teeny bit to use probes. Without full load and unplugged i want to say it was 118 or better. This was all at pedestal. The outside receptacle on the rig read 117 along with the camp pedestal. However the ems on inside is reading low? 

[Lori]

The campground has new meters, new receptacles, and new breakers this year. The pedestal has been checked and is wired and working properly. The person owning rig is super concerned because it is brand new and expensive and reading low voltage. 

[Kirk W]

25 minutes ago, Lori said:

Hello, a voltage meter and it was read with the 50 amp plug plugged in. They pulled it out a teeny bit to use probes. Without full load and unplugged i want to say it was 118 or better. This was all at pedestal. The outside receptacle on the rig read 117 along with the camp pedestal. However the ems on inside is reading low? 

If the readings were taken with the very same amount of current draw on both sides, that does indicate a problem somewhere between the points the two readings were taken. After 40+ years in electric service work, I have never seen a power cord cause this, which from what you describe would be about all that is between the two points of measurement.  Of course, this also assumes that the measurements were accurate and the load current was exactly the same for both readings.

27 minutes ago, Lori said:

The person owning rig is super concerned because it is brand new and expensive and reading low voltage. 

1

Without being there to check things myself, I can only guess what is happening. My suspicion is that the load was not the same when the pedestal readings were taken. 

32 minutes ago, Lori said:

The outside receptacle on the rig read 117 along with the camp pedestal. However the ems on inside is reading low? 

I hate to tell you this, but the outside outlet of the RV is supplied by the power passing through the EMS so it is not possible for the readings to be accurate if taken at the same time, or the EMS is not properly wired in the RV.

[Lori]

Thanks!

[Fulltimer51]

The windup reel is also an electric contact point.  As is the transfer switch if generator prepped. Anything is possible in a new rig. I would check the voltages at the circuit breaker panel.