Electrical help needed! Lost 50 amp shore power. Is it the power cord?

[Cate&Rob]

TedS Ted, More than likely the transformer feeding the campground is going bad. I remember a while back a discussion of neural measuring the current, at one campground the neutral showed the full current of the camper when on 50A service, at the next it did not. This means that someone probably wired the Pedestal with both legs on the same Hot which would show 0 Volts between the 2 hot legs. No harm to most campers as they run everything on 120V.

This would appear to be OK . . . until the neutral in the RV or the cord becomes overloaded. Each of the hot legs and the neutral are sized to carry 50A. This only works if L1 and L2 are out of phase (a divided 240V feed). If L1 and L2 are on the same phase, the neutral would be required to carry twice the current. If this were the situation, L1 to L2 would show 0 volts, but either L1 or L2 to neutral would show 120 volts. Going back to the original post L1 to neutral showed 120V but L2 to neutral showed 0 (actually 3) volts. I don't think L1 to L2 was ever measured to confirm. Since the cord turned out to be OK, the cause is most likely a bad breaker in that post. If all posts on that line showed the same problem, this could have been a problem with the larger breaker at the panel, or the transformer.

Rob

[TedS]

Connecting both legs from the transformer would make a big spark. The voltage between the two legs is 240v. Perhaps only one transformer leg was wired to both terminals of the pedestal double 50 amp breaker. That would cause all current to flow through the neutral, but only one 120v leg of the transformer and 0v L1 to L2 at the receptacle. An unbalanced feed.

[Jlawles2]

TedS Ted, More than likely the transformer feeding the campground is going bad. I remember a while back a discussion of neural measuring the current, at one campground the neutral showed the full current of the camper when on 50A service, at the next it did not. This means that someone probably wired the Pedestal with both legs on the same Hot which would show 0 Volts between the 2 hot legs. No harm to most campers as they run everything on 120V.

[TedS]

Jlawles2 , see the diagram in post #21.

[Jlawles2]

I would be suspect of something at the transformer causing L2 to drop out like that. If it was a distribution issue, it most likely would be there at all times.

Remember a transformer takes high voltage and lowers it to 120 V. Single leg of HV makes 2 legs of 120V.

Also note, in a properly designed system the L1 and L2 should be balanced. This is simply accomplished by putting all of phase A on L1 in odd number sites and phase B on L1 in the even numbered sites.

Even though campers use a 240V receptical on the 50A, it's possible that one overly sized Phase is brought into the pedestal and split into L1 and L2.

[bertschb]

Thought I'd give you guys an update. We spent the last two days at a park in Salt Lake City with very low voltage but the 50 amp cord worked both days. We arrived at a new park today called Willow Winds near Zion. I checked the voltage when we arrived this afternoon and it was 117/117. So nice to see voltage over 110 after the last week of poor electrical service at other parks.

At this point I think the problem I shared in my first post in this thread was due to the power at the pedestal. My 50 amp cord has worked fine since I left that park. We are staying here for a week then moving again to several other parks in July. If I don't experience any further electrical problems by the end of this month, I'll give my power cord a clean bill of health.

Thank you all for your comments. And by the way, if you're reading this thread and haven't purchased an EMS yet, get one now! You will eventually stay at a park with lousy power and it could save the electronics in your RV.

[ncitro]

I've never seen a pedestal opened up but I've always assumed that a 59/30/20 pedestal was fed with one feed, in parallel with a couple other sites upstream and downstream, all fed by some kind of main breaker panel, with that branch fed by a (hopefully) appropriately sized breaker. If that's the case, and all the 30 amp outlets are fed by the same phase(let's assume L1), then I could see the voltage being imbalanced at his 50 amp connection. A large drop on L1 from a bunch of 30 amp rigs running their A/C. Obviously does not explain it dropping to zero (or near zero), but I know I've seen campgrounds where one phase drops below 104 and trips my EMS where the other phase was happy at 120V all day long.

[Cate&Rob]

bertschb

This is pointing to the problem being in the previous park electrical supply system . . .

Rob

[bertschb]

He swapped the entire cord, he didn't just add an adapter.

Correct Howard. I have the factory 50 amp cord as well as a 30 amp cord with a 30 to 50 amp adapter. The 30 amp cord was plugged into a separate 30 amp outlet on the pedestal and worked for two afternoons/evenings with no problems.

To recap today- We arrived at this new park today at around 1:00PM MT. Voltage at this park is known to be low based on reviews from other guests. The weather conditions are similar to the last couple of days in Idaho. Low 90's and the afternoon sun is directly on the power cord.

I plugged in the 50 amp cord and these are my readings so far:

Monday June 28th
1:00PM L1-107v L2-110v
2:15PM L1-108v L2-110v
5:00PM L1-106v L2-113v <------ My EMS cuts power at 104
6:30PM L1-110v L2-111v
8:30PM L1-110v L2-114v

50 amp cord worked fine all day and night

Tuesday June 29th
6:00AM L1-119v L2-121v
2:00PM L1-107v L2-111v
2:30PM - Lost power for a split second. EMS showed PE4 error (low voltage on L1)
4:00PM L1-108v L2-107v

[howson]

Misread his original post (again). He swapped the entire cord, he didn't just add an adapter. That implies there was a separate 30A connector on the pedestal. So there's a few variables still in play -- different cord and different outlet on the pedestal.

[TedS]

The 30 amp post outlet uses one of the two 120v legs at the post. If L1 is the same as 30 amp line, then the L2 in the post could have the problem. Or the 50 amp breaker on the post could be bad.
You are correct about the adapter connecting the one 30 amp hot to the two 50 amp hots.

[howson]

The 30 amp connection that worked may have been on the park leg that was not the problem leg.

That's the interesting part of this discussion I've been trying to wrap my head around. The 30A adapter ties the two legs together, right, as shown in pic below? (Graphic below from RV.Net forum.)



Since @bertsch had success with this adapter, the bad leg must have been "open" somewhere.

The conclusions are still the same--park has an issue (somewhere from the output of the transformer to the output of the pedestal) or Brian has a bad cord or receptacle on his trailer. If either of the two latter are the issue, we'll find out soon enough. The cord (or trailer) won't get better all by itself.

Howard

[TedS]

The 30 amp connection that worked may have been on the park leg that was not the problem leg.

[Canyonlight]

Thanks Brian bertschb and Rob Cate&Rob for your responses. Most of you here know that I did not even play an electrician on TV. Heck, they wouldn't even let me read the script ! I have basic understanding but have learned so much from many of you here who are really well versed.

It is just interesting that a trending number of posts regarding electrical challenges here on this forum an elsewhere have been showing up the last several days particularly in the VERY hot west of the Rockies area from Canada to the South Pole. Coincidence or could there be some strange things going on impacting various electrical systems in the RVs.

Extreme and persistent hot or cold conditions conditions can do some strange and potentially damaging things. Thank goodness for our electrical well versed folks here to help diagnose and correct challenges !

Dan

[Cate&Rob]

bertschb Canyonlight

The situation with L1/L2 @ 107V/110V is indicative of park system overload. Both legs drop more-or-less together until one trips the 104V EMS threshold. This is the classic "brown out".

The situation that Brian encountered at the previous park with one leg normal and one leg gone indicates a wiring problem. The park?, or the power cord?, or the trailer? If it doesn't re-appear, it was the park. If it does, it is likely the cord since using the 30A cord solved the problem.

Rob