Interesting electrical problem

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BinaryBob

BinaryBob

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Spent one night at a state park campground near Rockford, IL yesterday. The 30 amp breaker at the post tripped. I found a maintenance guy who said they would check it out. two guys came and replaced the GFI at the post. Still tripped.
The older guy: "These are expensive breakers that are sensitive. You need to check your manuals and figure out what's wrong in your rig"

The younger guy (out of earshot of the older guy): "This happens a lot with newer rigs. Doesn't seem to happen with the older ones. The wiring is very old and we've had a lot of rain lately."

My control panel read, "Wiring error. Neutral = ground"

I'm currently at a very nice 50 amp campground having no problems at all.
It appears their post wiring was kaput. Out of curiosity, can any of you electrical gurus explain this error message?
 
GFCI breakers trip when there's any difference at all between the currents in the hot line going out to the trailer and the neutral line returning from it, on the theory the missing current may be going to ground by shocking a person.  It doesn't take much (4-5 milliamps or 4-5 1/000 of an amp)  to unbalance the currents and trip a GFCI breaker.

Wet weather can create leakage paths by dampening dust in an outlet and making it conductive.  There's no reason why "new rigs" should trip a GFCI any sooner than an older rig, unless the manufacturer goofed and connected ground and neutral inside the power panel.  You do this at the main panel, in this case the campground's main distrubution panel.  Panels located elsewhere including in the RV are subpanels and should keep ground and neutral seperate.

The reason the GFCI doesn't trip on a 50 amp connection is 50 amp outlets aren't GFCI protected.

 
Thanks Lou.
I was at a 30 amp site a month ago with no problems. I do use a surge protector at the post.
If I read you correctly, this was a problem at the post and not in my MH ?
 
"The reason the GFCI doesn't trip on a 50 amp connection is 50 amp outlets aren't GFCI protected".
Diamond Lakes Regional park campground in Augusta, Ga has gfcis on 20, 30, and 50 amp. I stayed there for a week last year on 50 amp gfci and had no problems.
 
I've heard that the Corp of Engineers is now installing 50A GFCI's in their parks. Maybe even retrofitting the older ones.  50A GFCI breakers are now generally available (at about 3x the price of non-GFCI).
 
Some of the EMS units will trip 50 amp breakers due to the surge protection devices leaking current from hot to neutral..  Mine did as there was a campground we stayed at when heading to Portland OR with the 50 amp GCFI breakers.  When we installed the 50 amp service the electrician would not install the GCFI as he said we would trip it as he had done at his house.
Just  word of caution.
 
This looks like a good place  to jump in with my recent interesting electrical issue. We were at the Napa county fairground RV park. Paved roads, concrete sites, and 30/50 amp electrical hook ups. We were hearing a single "beep" our first night and couldn't locate the reason. It was about 2230 hours and it would only beep about once every 5 minutes or so. 

My sharp ear wife figured out from the bedroom that the microwave was beeping.  And then when I walked in to talk to her, the transfer switch clunked.  Then we figured out that the power was being taken off line by the Surge Guard.  My electrical volt meter had shown a pretty low line 1 voltage all day of about 109-106 volts.  There were many other rigs, many of them 30 amp power. 

So I went outside to  check the Surge Guard and when monitoring the readout, a code flashed that translated to high voltage on line 2.  Sure enough as I was watching, line 2 was at 132 volts, then bumped to 133 volts and the Surge Guard took it off line. 

Now this was at 2230 on Labor Day weekend and the chance of getting a service guy to our county campground was slim to none. So I took a shot and pulled out my line switcher pig tail and plugged it in. I was hoping that if I could put some draw on the line maybe it wouldn't go up so far. 

Sure enough when the surge guard reconnected it was showing 120 volts on both lines.  It stayed that way for the rest of the weekend, and then I left Tuesday morning. I have never experienced this before, this was a first for me.  Can anyone come up with a logical reason for behavior like that? 
 
The only thing that will cause a HIGH reading on one side of a 120/240 volt circuit is a "soft neutral" that's not anchoring the midpoint of the 50 amp circuits to 0 volts.  Having simultaneous low voltage on the other half (109 volts) confirms the neutral isn't doing it's job.

Since the condition cleared when you removed the plug and inserted another one tends to show the second plug made a better connection than the first.  There might have been a bit of dirt and corrosion that moving the plugs in and out kicked out of the way, or maybe the prong angled a bit differently on the second plug to make a better connection, who knows.

If the soft neutral was caused by wiring further upstream, such as the 30 amp rigs pulling more current from one leg than the other, the problem wouldn't have cleared when you inserted the second plug.  The unbalanced voltage would have just swapped legs.
 
So the "soft neutral" is just a loose wire somewhere in the circuit?
Click to expand...
Loose, corroded, partially broken, or just plain disconnected. Anything that inhibits the neutral from carrying all the amps flowing in the combined L1/L2 circuit.

On the RV side, common problems that cause neutral wire issues are a broken neutral connection at the shore plug or a loose or corroded neutral wire connection at the auto-transfer switch.

On the park side, the most common problems are right at the pedestal, e.g. broken neutrals and corroded connections. A "surge guard" or EMS will detect a totally broken (disconnected) neutral on the pedestal, but typically misses one where there is heavy corrosion or a partial connection.  The neutral is good enough to pass a quick voltage or continuity check but fails when the amp load gets higher.
 
Thanks for the clarification Gary. At this point I am betting it was on the pedestal. Since I have been on 50 amp pedestal's both before and after Napa and the problem has vanished. 
 
Lou Schneider said:
GFCI breakers trip when there's any difference at all between the currents in the hot line going out to the trailer and the neutral line returning from it, on the theory the missing current may be going to ground by shocking a person.  It doesn't take much (4-5 milliamps or 4-5 1/000 of an amp)  to unbalance the currents and trip a GFCI breaker.

Wet weather can create leakage paths by dampening dust in an outlet and making it conductive.  There's no reason why "new rigs" should trip a GFCI any sooner than an older rig, unless the manufacturer goofed and connected ground and neutral inside the power panel.  You do this at the main panel, in this case the campground's main distrubution panel.  Panels located elsewhere including in the RV are subpanels and should keep ground and neutral seperate.

The reason the GFCI doesn't trip on a 50 amp connection is 50 amp outlets aren't GFCI protected.

The 30 amp should not be GFI protected either.
Click to expand...
 
Gary RV_Wizard said:
I've heard that the Corp of Engineers is now installing 50A GFCI's in their parks. Maybe even retrofitting the older ones.  50A GFCI breakers are now generally available (at about 3x the price of non-GFCI).
Click to expand...

Let the headaches begin.
 
There is no technical reason why 30A and 50A outlets are typically not GFCI-protected.  Strictly a cost vs benefit decision.  In the RV world, those outlets are feeding subpanels which do have GFCI branch circuits where appropriate, so the likelihood of short circuit danger is tiny. Not zero, but less than a wall outlet that mostly services consumer-grade gadgets and beat-up old extension cords.
 
I have seen 30 amp GFCI in fact been plugged into 'em

50 amps.. I kind of wonder since you have two Hots and a neutral you need so do some rather fancy math to tell if there is an imbalance

"Does L1-L2=N?" type math.  That's going to add cost and cost reliability.

 
50 amps.. I kind of wonder since you have two Hots and a neutral you need so do some rather fancy math to tell if there is an imbalance
Click to expand...
Not really fancy - it's just the algebraic sum of the L1 + L2 currents. It does take two current sensors rather than one, though. Maybe why [so far] they only make 50A GFCIs as breakers.
https://www.homedepot.com/p/Square-D-Homeline-50-Amp-2-Pole-GFCI-Circuit-Breaker-HOM250GFICP/100169582

I have seen a 30A/240v GFCI packaged as a portable unit.

https://www.gordonelectricsupply.com/p/Cooper-Gfi23M144-30A-240V-Man-Gfci/6046285
 
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