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Direct Link To This Post Topic: 50 or 30 amp
    Posted: 26 Jan 2019 at 7:56am
Originally posted by furpod

Power isn't "pushed" through wiring, it is pulled. So unless a bad or dead short happens somewhere between the post and the campers power distribution box, no issues. And if it does, as soon as it pulls more than 50A, which it will, the breaker at the post will trip.

There probably are people who run the air conditioner, the microwave, a hair dryer, a coffee maker, an electric heater and a few other things all at once, but I've never tripped a 30 amp breaker at the post.  Has anyone else?

It seems highly unlikely that short (sorry) of a fault in the power cord it would be likely that a 50 amp breaker would ever trip when used on a 30 amp trailer.  The 30 amp box in the trailer, with it's 30 amp main and 10 and 15 amp circuits, is going to protect from most stupidity or shorts in your hair dryer.

I'm not saying there aren't ways to screw up.  I've never had to use a 50 amp circuit.  If I did I guess I'd want an adapter that only let one leg of the current into the cable from the post to the Pod.

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Direct Link To This Post Posted: 26 Jan 2019 at 7:39am
In looking back through a couple years of RVIA data.. I can't find a single instance of a fire, or damage caused by,a camper being hooked to a higher, or lower rated, outlet. There are several reports of damage and fires from a poorly connected hookup, Some are user error, some are just worn/corroded connections.

The 30A circuit breaker is going to protect the camper itself. What is *theoretically* in danger is the umbilical cord itself, but again, I can't find any reports of an actual, undamaged, proper RV power cord failing.

Power isn't "pushed" through wiring, it is pulled. So unless a bad or dead short happens somewhere between the post and the campers power distribution box, no issues. And if it does, as soon as it pulls more than 50A, which it will, the breaker at the post will trip.

But again, I can find no reports of either happening. At least that have been covered by a RVIA report.
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Direct Link To This Post Posted: 26 Jan 2019 at 4:33am
Well I misread the specs on the EMS I was looking at last night when I wrote the last post. I thought I saw overcurrent protection as one of its features but it was only a current indicator. i was looking at the Progressive Industries EMS PT30X.

In looking further just now I wasn't able to find any that provide overcurrent protection, meaning that none appear to both monitor the current flow through the device AND disconnect if that exceeds the rating. Too bad because it seems like it would be an easy feature to add at least in models that are already monitoring current. 

So, I will rephrase:

No, an RV EMS will not protect you from the overcurrent risk resulting from connecting a 30A RV electrical system to a 50A pedestal. It protects from several other conditions that are worthwhile to monitor but not that one. 

If anyone knows of an EMS that does have an overcurrent disconnect feature please let us know. 


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Direct Link To This Post Posted: 25 Jan 2019 at 9:08pm
Depends if you're using a 50A EMS or a 30A EMS. 

The 50A EMS won't protect you from excess current flowing into your trailer's 30A power cord, connector and internal conductors in the event of a 50A fault in that circuit, because the EMS is going to think that 50A is a normal current. Might go 20 years like that and never have a problem, but the risk is there the whole time. 

if you're using a 30A EMS directly after the 50 to 30A dogbone that would protect you. 




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Direct Link To This Post Posted: 25 Jan 2019 at 3:05pm
Most places I ever camp have a 50, 30, and 20 amp plug in on the power post. I have used the 50 amp more than i've used the 30 amp, because the 30 amp doesn't always fit right. I have a nice adaptor that works great. I (gulp) assume..... that my EMS would protect me if there were any problems with volts or amps. I have a progressive hard wired system. I always run shore power into the power receptacle, and I always run a 20 amp extension cord from the 20 amp plug in, to a power 20 amp power strip for the outside electronics, like the ice maker, or occasional crock pot power. I've never had a power issue in 2 1/2 years

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Direct Link To This Post Posted: 24 Jan 2019 at 11:16pm
If you encounter a campground that only has 50A connections, chances are that the campground office will have 50 to 30A adapters that the office will loan you. That happened to us when we stayed at an RV park in West Yellowstone, Montana. That has been the only time so far that we have encountered that situation.
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Direct Link To This Post Posted: 24 Jan 2019 at 9:21pm
Great info guys. I was thinking of getting a 50 to 30 amp dog bone. But now don't think I will.
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Direct Link To This Post Posted: 24 Jan 2019 at 5:57pm
Thank you all for your information. 
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Direct Link To This Post Posted: 24 Jan 2019 at 5:32pm
The issue with connecting to  a 120V system using one of the two hots from a 240V split phase service is there but it is readily solvable (the dogbones terminate one of the two hot leads internally), and the 50A 2 pole breaker will trip if either leg individually exceeds that rating.  

The real concern is that you are connecting a 50A service to an electrical system designed for only 30A. That creates a fire risk and is an NEC code violation. The connector on your trailer says not to do it. Lots of people do it anyway, up to each individual to assess this risk and decide for themselves. 

BTW, current electrical code requires pedestals with 50A service to also have 30A  and 15A service, but until the campgrounds update their electrical systems you won't necessarily find this. 


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Direct Link To This Post Posted: 24 Jan 2019 at 2:12pm
Originally posted by offgrid

The main caveat with using a 50 to 30 amp adapter is safety. Some of us are ok with it, some are not, and FR doesn’t recommend it. There is a long thread on that issue on this forum you could search for and reach your own conclusions.
The main issue being that a 50 amp connection is split phase. IOW, it has two hot leads. To convert it to 30 amp, you only pull one of the hots, and leave the other one unterminated. So that leaves a couple of issues. One is that the unterminated lead must be protected from touching anything that it shouldn't. Two being the 2-pole breaker is only sensing current on one of the hots (instead of both of them). Just something to be aware of.
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