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

[Cate&Rob]

bertschb

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

Rob

[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.

[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.

[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.

[TedS]

Jlawles2 , see the diagram in post #21.

[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]

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.

[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