RV Adapter Plug

[LandShark]

When using a 50 to 30 amp adapter, how many amps are available at the plug?

 

[RustyJC]

Theoretically, 50 amps are available from 1 leg of the power pedestal's 50 amp receptacle (remember, 50 amp service has 2 legs of 120VAC 50 amp power available), but under normal circumstances you can never draw more than 30 amps without tripping the main 30 amp breaker in the RV. That main breaker in the RV provides your current limiting protection. The only risk would be if you developed a high resistance short in the power cord such that the current increased to almost 50 amps through the adapter and power cord but never went above 30 amps in the RV - in that case, neither breaker would trip. The risk of that happening, however, is minimal.

Rusty

 

[LandShark]

Rusty:
Thanks for the info. I didn't realize that each leg on a 50 amp rv plug would be 50 amps: I was thinking 25 on each leg.
I ended up building a 50 to 30 adapter which can have either hot leg supply the line for my trailer. The reason for doing this is that my 30 amp service at the rv park I'm staying in, has only 118 volts and it drops to about 106 with the ac and coffee pot on. I measured the legs on the available 50 amp service and got 118 on one side and 125 on the other. The 50 to 30 amp commercial adapter I have of course uses the 118 leg.

Haven't had a chance to test the new adapter because it's been raining all week.

 

[RustyJC]

HERE is a full explanation of 50 amp RV service.

Rusty

 

[Bill Stockard]

I carry a 50-amp to 30-amp adapter in my Lance truck camper that is equipped with a 30-amp electrical cord. Over the years, I've found that some RV parks have badly burned contacts in their 30-amp service receptacle from RVers overloading the circuit and/or lack of proper maintenance. I've found the 50-amp receptacle, if available, is usually in much better condition. I use my 50 to 30-amp adapter in these situations and don't chance burning the contacts in my camper's power cord from the poor connection.

Bill

 

[Bob4x4]

It's a bit scary when you start reading about all the different faults in rv parks that are either poorly maintained or designed

 

[Bill Stockard]

It's a bit scary when you start reading about all the different faults in rv parks that are either poorly maintained or designed

... and that's why I check the receptacle before plugging in my RV.

Bill

 

[jeepit]

... and that's why I check the receptacle before plugging in my RV.

Bill

Good advise Bill!
Thanks for the heads up!

 

[Darmeisner]

LandShark



Rusty:
Thanks for the info. I didn't realize that each leg on a 50 amp rv plug would be 50 amps: I was thinking 25 on each leg.
I ended up building a 50 to 30 adapter which can have either hot leg supply the line for my trailer. The reason for doing this is that my 30 amp service at the rv park I'm staying in, has only 118 volts and it drops to about 106 with the ac and coffee pot on. I measured the legs on the available 50 amp service and got 118 on one side and 125 on the other. The 50 to 30 amp commercial adapter I have of course uses the 118 leg.

Haven't had a chance to test the new adapter because it's been raining all week.

For others wanting to do the same thing, but don't have the facilities to make that adapter:

ParkPower by Marinco 169AYRV RV Electrical Power Adapter (Double 30-Amp, 125-Volt to 50-Amp Straight Blade) (on Amazon)

Not cheap, but it will do that job or allow 2 30 amp RV's to share a 50 amp receptacle.

Dar

 

[LandShark]

Finally got to try my new adapter. It works as I had hoped; I now have about 8 volts more in the RV. My hope is that the AC (which runs continuously in FL these days) will last a bit longer.

Dar: That Marinco 169AYRV is a nice piece and a good option for most. The $100+ price is a bit much though.

 

[Bill Stockard]

Finally got to try my new adapter. It works as I had hoped; I now have about 8 volts more in the RV. My hope is that the AC (which runs continuously in FL these days) will last a bit longer.

Dar: That Marinco 169AYRV is a nice piece and a good option for most. The $100+ price is a bit much though.

The RV park probably wired the electric hookups on the cheap by connecting several RV pads on the same circuit coming from the park's main circuit breaker box with several RVs running on the same 120 volt leg of the 240 volt circuit.

Bill

 

[Road Dog]

Why is that on the cheap? I would suspect that many RVs use a 50-30 adapter and end up using the same leg of the 120/240 system.

 

[RustyJC]

Bill stated that the campground owner wired his pedestals "on the cheap" and pulled only 1 leg of the 120/240 volt center tap neutral service to handle the hot legs of the 30 and 20 amp receptacles on multiple pedestals. Good practice would be to balance the loads by wiring half of the pedestals on L1 and half on L2 for the 30 and 20 amp service, or if 50 amp service is present at each pedestal, alternate using L1 and L2 when wiring the 30 and 20 amp receptacles at each pedestal. You shouldn't wind up with ALL your 30 amp receptacles on 1 leg, or the results reported by the OP will occur - the voltage will be pulled down on the leg that's handling all the 30 amp demand.

The owner at the storage lot where we keep our RV did the same thing on a different application. We have 30 amp receptacles in our covered storage bays, and they work just fine. He has a 50 amp receptacle on the wall of his shop adjacent to the wash rack, however, and BOTH hot legs of the 50 amp receptacle are wired to the same hot leg. Besides risking overloading the neutral conductor on the shore power cord, our RV's power management system doesn't see 240VAC across the 2 hot legs and defaults to 30 amp service (as it should) when the RV is plugged into this 50 amp receptacle.

Rusty

 

[SnoKing]

Just remember if you have full 50 amp service that it the neutral goes away, you burn up everything in the trailer/MH. Friend here is a 7K and claiming replacing things that burned up in his MH and a $70 per night park in California. If I had 50 service I would have a good smart isolation transformer!

 

[mwilson]

This has been a very interesting thread and I have learned from it. I never investigated the 50 amp service before and did not realize that it was a basic 220/240 volt feed as far as wiring goes. Only the outlet differs.
I've done a bunch of wiring over the years as a Time - Life (that's what our local electrician calls me) DIY type electrician, just never tangled with a 50 amp RV service.

Had to learn some three phase as well to keep this joint running over the years.

Mike.

 

[RustyJC]

Just remember if you have full 50 amp service that it the neutral goes away, you burn up everything in the trailer/MH. Friend here is a 7K and claiming replacing things that burned up in his MH and a $70 per night park in California. If I had 50 service I would have a good smart isolation transformer!

That's why I'm glad our Mobile Suites has a permanent, hard-wired Progressive Industries power protection system looking at the incoming power to the RV's power distribution center (breaker panel). It will detect a floating or dropped neutral and shut off incoming power to the RV within milliseconds; if that condition exists when the shore power cord is initially plugged in to the pedestal, it will never clear its start-up diagnostic and will not admit power to the rig, but instead will just flash the appropriate error code.

Our daughter and son-in-law were using a plug-in power protection system at the pedestal last year when their RV's shore power cord lost a neutral conductor. I still remember that phone call from the daughter asking what could cause smoke to come out of the microwave when they hooked up at a new campsite! It cost their insurance company over $7,000 to replace all the 120VAC appliances that were fried when hit with 240VAC. Their plug-in power protection system couldn't see the missing neutral since the fault was on its output, not input, side.

Needless to say, they added a Progressive Industries power protection system like ours while the repairs were being made.

 

[Road Dog]

Bill stated that the campground owner wired his pedestals "on the cheap" and pulled only 1 leg of the 120/240 volt center tap neutral service to handle the hot legs of the 30 and 20 amp receptacles on multiple pedestals. Good practice would be to balance the loads by wiring half of the pedestals on L1 and half on L2 for the 30 and 20 amp service, or if 50 amp service is present at each pedestal, alternate using L1 and L2 when wiring the 30 and 20 amp receptacles at each pedestal. You shouldn't wind up with ALL your 30 amp receptacles on 1 leg, or the results reported by the OP will occur - the voltage will be pulled down on the leg that's handling all the 30 amp demand.
Rusty

You're completely right about how it should be wired but the OP was asking about an adapter so I assume there's a single 50A plug and no 30A. Adding more plugs means adding more breakers to the panel. If there's a single 50A then L1 and L2 could be flipped on alternating panels (if that's even allowed) so that 50-30 adapters would use different legs.

 

[RustyJC]

... but the OP was asking about an adapter so I assume there's a single 50A plug and no 30A.

Well, that's a possibility, but many RVers will plug their 30 amp RV into the 50 amp receptacle (using an adapter, of course) if the 30 amp receptacle has burned contacts or other wear and tear from age and overuse. In many campgrounds, the 30 amp receptacle sees a lot more use than the 50 amp.

L1 and L2 are interchangeable on the 50 amp receptacle hot leg terminals, so if I were wiring a campground, I'd probably do just what you suggest and alternate the 50 amp receptacle hot leg wiring.

Rusty

 

[Bill Stockard]

After we built our new home in northeast Texas, I built a long level concrete RV pad with full hookups for friends and relatives to park their RV when visiting us. Along with water and sewer connections, I installed a 30-amp and a 50-amp RV electric receptacle box In the attached photo, the box on the left is a 50-amp connection and on the right is a 30-amp. I wired the 50-amp with 4-gauge and the 30-amp with 8-gauge wiring in separate conduit and on separate circuits. In addition to being wired with a ground back to the main circuit breaker, each of the RV outlets are grounded to earth with a ground rod at the post. The main circuit breaker box is about 30 feet away and mounted on the service entrance meter pole.

Bill

 

[mwilson]

Looks like a good way to wind up with squatters...............Especially after the winter that we are just finishing...:-laf