Well if it's July, I must be discussing power issues at the campground . . . Lately, we've been experiencing voltage issues which the Progressive EMS has been seeing and shutting down power until it's happy. Talked again with the campground owner who's listening but skeptical that an issue exists. Last year, he brought in an electrician who found and corrected a lot of loose connections. That took care of the low voltage but the occasional high voltage continued. This past week seems high voltage has been the rule and the system cuts down any time of the day or night. The same electrician came back today saying the power at the pole was fine and wondered if the issue isn't in my trailer electrical. One think he pointed to was the 122V measured at the pole and 128V flashing on my EMS display. Any idea why we'd see higher voltage at the rig compared to the post? This is a 50amp hardwired EMS that has had a Hum since installed in 2015 - it this normal?

Subscribing. Curious about the hum and differing voltages...

Call Progressive. My hard wired 30 A EMS had the same symptoms from day 1. It always displayed 4 volts higher than the actual voltage. They told me how to adjust the unit to read the same as the input voltage. Maybe yours just needs this adjustment or maybe its bad. Can't help with the hum. Hope this helps

One is reading true power and the other is reading apparent power.

AUwing2 wrote:Any idea why we'd see higher voltage at the rig compared to the post? This is a 50amp hardwired EMS that has had a Hum since installed in 2015 - it this normal?That is a poor neutral connection somewhere and an unbalanced load. Really need to verify using same meter in both places.Master electrician knows this straight away.

time2roll wrote:AUwing2 wrote:Any idea why we'd see higher voltage at the rig compared to the post? This is a 50amp hardwired EMS that has had a Hum since installed in 2015 - it this normal?That is a poor neutral connection somewhere and an unbalanced load. Really need to verify using same meter in both places.Master electrician knows this straight away.Agree with this. The EMS is likely reporting the opposite leg from the one measured at the pole. Is there a way for the EMS to display both sides? I'd bet the other side is 122V, making them average 125V.Maybe I'm assuming too much. When you say 50A, I assume you mean your RV has 50A split with a 4-pin plug? If not, disregard the above.

Pole voltage VS EMS Voltage | Good Sam Community

17 Replies

afidel
Explorer II
Jul 14, 2017
Also you really, really want to use an all plastic (or plastic and ceramic) trimpot adjuster of the appropriate size. My worst encounter with electricity was adjusting a trimpot in a Sun LC workstation (like an early iMac, computer and monitor together), screwdriver slipped and hit the fly transformer and I went flying several feet and hit the wall, screwdriver had a chunk taken out where it partially vaporized. You might not get thrown by the innards of the EMS, but worse 240V can make you clench up and with 50A coursing through you it's unlikely you're heart would go undamaged.
wnjj
Explorer II
Jul 14, 2017
AUwing2 wrote:
Thanks - I appreciate the responses and help thinking this thru. I'll call Progressive for a calibration procedure.

I agree there's a poor neutral somewhere that's the culprit. The electrician is a local small town guy and may not be a master. Nice enough guy but a bit defensive of his prior work "cleaning-up" the system. I need to up my skill to help trouble shoot the open / bad neutral.

troubleshooting the source of the issue . . .
If I connect to 20 or 30A, I should see equal voltage on the Progressive display correct? (20A & 30A having a single load that's shared by the 2 loads on my 50A trailer)

Make sure the poor neutral isn't your cord. Measure both legs at the pedistal and then hook up and measure both in your panel.

With a dog bone on 20 or 30A, yes both sides should match or your unit needs calibrated.
WA4HTZ
Explorer
Jul 14, 2017
Sound Guy's picture shows the trim pot very well for his 30 Amp EMS. On my 50 Amp unit there are two identical trim pots. If you look closely at the picture just to the left of the trim pot, you can see where there is a place for the second pot on the circuit board. On my 50, that spot is populated. Oh, and my contactor doesn't hum but it sure makes a heck of a CLUNK when the time delay expires!

Ken
pianotuna
Nomad III
Jul 14, 2017
Thanks for the picture Sound Guy
AUwing2
Explorer
Jul 14, 2017
SoundGuy wrote:

I've not opened a 50 amp version but there would either be a similar dual trim pot or perhaps two separate pots, one for each leg. However, I wouldn't fool with this unless using a calibrated meter, otherwise you'd just be guessing. ;)

Thanks for the picture and advise. Mine in buried behind stairs, panels and the converter so there's no way I'm going in without a calibrated VM and well understood instructions. To my calibrated ear, the hum is no different today than it was a couple years ago when I installed it. Installed a 30A EMS on our previous trailer and never knew it was there - unless it detected something it didn't like of course.
AUwing2
Explorer
Jul 14, 2017
Thanks - I appreciate the responses and help thinking this thru. I'll call Progressive for a calibration procedure.

I agree there's a poor neutral somewhere that's the culprit. The electrician is a local small town guy and may not be a master. Nice enough guy but a bit defensive of his prior work "cleaning-up" the system. I need to up my skill to help trouble shoot the open / bad neutral.

troubleshooting the source of the issue . . .
If I connect to 20 or 30A, I should see equal voltage on the Progressive display correct? (20A & 30A having a single load that's shared by the 2 loads on my 50A trailer)
SoundGuy
Explorer
Jul 14, 2017
neschultz wrote:
My hard wired 30 A EMS had the same symptoms from day 1. It always displayed 4 volts higher than the actual voltage. They told me how to adjust the unit to read the same as the input voltage. Maybe yours just needs this adjustment or maybe its bad. Can't help with the hum.

Hum is merely the contactor (relay) ... carefully cleaning the contacts may reduce hum somewhat but it's nothing to be concerned about. I've located mine under the sofa and recently I've noticed it a little noisier than in the past so one of these days I'll clean those contacts with an eraser to see if that helps.

I calibrated my own EMS-HW30C - blue trim pot as shown on the lower left in this pic.

I've not opened a 50 amp version but there would either be a similar dual trim pot or perhaps two separate pots, one for each leg. However, I wouldn't fool with this unless using a calibrated meter, otherwise you'd just be guessing. ;)
wa8yxm
Explorer III
Jul 14, 2017
There is a possibility that the EMS is "Off" somehow.. Low posibility but still there. Compare readings on the EMS display when another voltmeter.

You said the park had LOW voltage issues.. but they took care of that. now you have HIGH voltage issues.....

Here is how that happened.. The campground's wiring is what I call Anemic, it's not up to carrying the full load of the campers there.. THUS the voltage loss in teh wires causes LOW VOLTAGE when you load it down.

THe park applied to the power company for a higher voltage "Tap" on the transformer.. This means that now under load you get the proper voltage. but when the load goes down your voltage is too HIGH.. It is still the park's fault but to catch it you need a recording voltmeter.. Something the power company can provide. but they may charge.
Second_Chance
Explorer II
Jul 14, 2017
I've never noticed a hum from our P.I. 50 amp hard-wired unit - but it's installed behind the electrical panel in the bottom of the buffet. When the weather got hot this summer, we started having problems with the system cutting out for low voltage (below 104 volts)... always on one leg. This happened at two different parks. Upon investigation, I discovered that both ACs - one 15K, one 13.5K - we on the same leg of the RV 50 amp service. I juggled breakers and put them on separate legs and haven't had a problem since. We've not had high voltage issues, so can't speak to that.

Rob
Old-Biscuit
Explorer III
Jul 13, 2017
Progressive Industries Hardwired EMS/Surge Protectors

Each unit includes a digital display, scrolling continuously through the power source information: Voltage(s), current, frequency, error code, and previous error code (if applicable).

Information for BOTH legs
First L1
Then L2

Voltage measured at power pole.......
Did 'electrician' measure L1 to Ground, L1 to Neutral, L2 to ground, L2 to Neutral, L1 to L2 ???

Or just measure ONE leg and call it good?

Got access to a different 50A source......??
Measure the voltage at receptacle and compare that with your EMS Display