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Old 10-05-2017, 02:24 PM   #1
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Converter going bad when on 50 amp shore, but not 30 amp shore

What would cause a 50 amp converter to behave normally as long as I only plug in to 30 amp power at the pole, but blow every time I use the 50 amp power at the pole?

It's not the converter, because this has happened with multiple converters. I guess I could have gotten 2 bad converters in a row, but seems unlikely.

Here is the history, and why I suspect 50 amp power coming in is at least part of the equation:

I have a Coachmen Freedom Express 292BHDS that is 50 amp. When we first bought it (2 years ago), we took it on it's 1st trip and plugged into 50 AMP shore power. Everything appeared to work fine, but 24 hours later the battery was at 1/3. It wasn't charging the battery. The AC and electrical outlets still worked fine.

A few weeks later we took it on a longer trip, again plugging into 50 amp power, by the end of the 2nd day light were dimming and battery was almost dead. It clearly was not charging the battery. The AC and electrical outlets still worked fine.

We took it in for service and it was declared to be a bad converter and was replaced.

We carried on camping many times, by chance on 30 amp poles, and had no further issues.

We then stayed in an RV resort with 50 amp power, and plugged in to the 50 amp pole. Again, 24 hours later, lights are dimming, converter is toast. The AC and electrical outlets still worked fine.

I use a 50 amp surge protector.

I'm now afraid to plug into 50 amp power even though my rv is set up to do so. I now always use a 50 amp to 30 amp dongle and plug into the 30 amp plug because I don't want to deal with another converter gone bad.

What could be going on in my camper that would cause 50 amp incoming power to kill my converter, but 30 amp incoming power to be fine?
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Old 10-05-2017, 02:41 PM   #2
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The only difference between RV 50 A and 30 A service is that the 50 A has two legs of 50 A, 180 out of phase from each other. I suspect this might be why your newer converter isn't working when on 50 amp service. I think you'll have to carefully inspect how the converter is wired to your breaker panel. Perhaps some leads were changed when the replacement converter was installed. The first one might have truly died, but the replacement works on 30 A but not 50 A, so that's why I'd suspect the wiring when it was installed.

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Old 10-05-2017, 02:43 PM   #3
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Nothing on 50A that would affect converter W/O affecting other 120V AC components

IS the AC Circuit Breaker for converter tripping?

What brand/model is converter?
How is it being determined converter is 'toast'?

Simple 120V AC input and 13.2V DC output.......if lower then 13.2V w/o a load THEN converter is/has failed

Same 120V AC
Like I said...other AC items would be affected also if main power was issue

Both AC Busses would be energized whether on 30A or 50A
50A ...two hot legs ---one to each buss in main panel
30A...jumpered inside adapter so both 50A legs are hot so both busses in main panel would be hot also
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Old 10-05-2017, 02:46 PM   #4
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Nothing ! If it was wired incorrectly it would fail instantly on 50 amp or not work at all on 30 amp..

30 amp and 50 amp service both supply 120 volts to the breaker panel. With 50 amp, 240 volts is avalable but rarely used.

The difference between 30 and 50 amp is the amount of power you can potentenly draw, not how much is going in.

If some of the wiring was crossed, supplying 240 volts to the converter, your dogbone adaptor wouldn't run the converter on 30 amp service.

You have a bad converter or a bad installation of the replacement.
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Old 10-05-2017, 06:30 PM   #5
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I would check the wiring of the converter AC input. It could be that the hot and neutral are reversed. The neutral and ground are handled differently by the 50-30 amp dog bone. It could also be a missing neutral to the converter. Your converter could be only getting a neutral when the dog bone is attached.
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Old 10-05-2017, 06:57 PM   #6
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Here is the wiring of both 30 and 50 amp service. There is no difference in the neutral and ground wiring.

That's not the problem.
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Old 10-07-2017, 04:57 AM   #7
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We had similar issues, had a tech tell me inverter was bad and needed replacing, I wanted to upgrade to a pure sign wave anyway so he changed it out, problem continued, different tech claimed switch was bad and replaced it, problem continued. During this three month ordeal I was usain an external charger to maintain batteries best I could. Had a third tech tell me he needed to tear apart my breaker panel and trace circuits and check system, lots of time (labor $$$) involved, I decided to not do this one, didn't make since to me, everything had been working correct. The only thing I could think of was there was a bit of arching on one leg of 50 amp power cord, looked like an isolated one time arch and not a big deal from looking at the plug plug on the outside. As a final effort, replaced cord and all was and has been good every since. I eventually cut and peeled off the end of the 50 amp cord the plugged into rig. Once I saw all the melting and arching that had occurred under the plug cover I realized or at least hoped that this was my problem. Turns out that this leg of my 50 amp service cord was the leg that fed my inverter and caused the aged batteries to die, and all of my electrical issues as opposed to 3 experienced techs evaluation and diagnosis. I believe that the issues was originally caused by a problematic campground post we were plugged into. I have pics of the cord end to post but have yet to figure out how to post them.
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Old 10-07-2017, 05:40 AM   #8
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The obvious place to start for me would be right at the input to the converter.

Pretty simple input wiring. Lift the wires, label them, and carefully prop them out so you can take voltage measurements. The converter will be safely out of the circuit so using 50 amps would not be an issue.

Take pictures before doing anything of course.

One cannot say "never" or "impossible" to some strange issue occurring. I have been troubleshooting for over 40 years.

The input voltages should not change. You should be able to use the generator as a substitute for the 50 amp shoreline but again, you need to test under all conditions.
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Old 10-07-2017, 06:25 AM   #9
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The converter takes 120 vac from yoru shore power (one leg of a 50 amp system) and makes 12 (well 13.6) DC. out of it.

There is, or rather should be, NOTHING that will cause it to work normally on 30 but "Go bad" on 50.. oh, how do you know it is "Going Bad"?

HOWEVER and open neutral will bother the converter, and several other things.. I have multiple volt meters in my RV.. one on each leg (I have 3 legs,, 50 amp L-1, L-2 and Inverter leg (Normally one of the first two but on occasion..)

A good voltmeter is the Kill-a-watt, it does other things as well
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Old 10-07-2017, 02:07 PM   #10
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If you had an open neutral, you would be replacing the microwave, TV, fridge control and lots of other things.
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Old 10-07-2017, 02:21 PM   #11
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The converter is a WFCO model WF9855. By "going bad" I mean they no longer functioned to charge the battery, as confirmed by the RV techs (grain of salt, I know). This has happened twice, seemingly in conjunction with plugging into a 50 amp source , and has not happened when plugging into a 30 amp source.

I now carry a spare converter with us, but I'd like to know if we have an electrical issue or just bad luck.
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