50 amp wireing - Montana Owners Club

daneboy · 03-27-2006, 05:37 AM

How is the 50 amp cord wired? I don't understan how the wireing goes from 3 wires with a 30 amp adapter to the 4 wire 50 amp cord? The 50 amp plug appears to have a ground, neutral & 2 hot legs but it's not 220.

What I'm planning on doing is, installing a small Honda generator in the front compartment and running a #10 cord under belly to the rear 50 amp trailer recptical. I'm not sure how to wire the plug. Would I just leave one hot leg unused? Your help is appreciated.
Jerry

cs413 · 03-27-2006, 06:58 AM

The 50 amp plug is 220-240 volts when the wiring is run from a TWO POLE breaker, which is two seperate circuits. One hot leg runs the 2nd a/c unit and the other hot leg runs the rest of the trailer.(Per Keystone) The legs are seperated in the electrical panel in the trailer. The 30-50 amp plugs adapt to each other internally in the plug, which is probably why they are so darn expensive. Somewhere on the forum are some good diagrams
showing all the plugs.
Curt

rvfirefighter · 03-27-2006, 07:17 AM

The difference is the 30 amp plug has a jumper that runs over to the other hot leg of the 50 amp plug. Thats why the 30 has 3 wires and a 50 amp has 4 wires.

jpbcny · 03-27-2006, 07:21 AM

If you plan a permanent install, I would suggest incorporating a Tranfer Switch for safety reasons. Here is a Link to a PDF download: TRANSFER SWITCH

JP

daneboy · 03-27-2006, 08:34 AM

Quote:

quote:Originally posted by cs413

The 50 amp plug is 220-240 volts when the wiring is run from a TWO POLE breaker, which is two seperate circuits. One hot leg runs the 2nd a/c unit and the other hot leg runs the rest of the trailer.(Per Keystone) The legs are seperated in the electrical panel in the trailer. The 30-50 amp plugs adapt to each other internally in the plug, which is probably why they are so darn expensive. Somewhere on the forum are some good diagrams
showing all the plugs.
Curt

daneboy · 03-27-2006, 08:40 AM

Thanks for the info. I'll try to find the diagram. I just want to use the generator while boondocking, so no transfer switch is necessary. It's a real pain to break out the heavy 50 amp cord then add two adapters so it can be pluged into a 15/20 amp outlet or generator.
Thanks,
Jerry

Broome101 · 03-27-2006, 09:07 AM

http://www.myrv.us/Pgs/RV/50amp.htm, try this link for diagram.

jpbcny · 03-27-2006, 10:05 AM

Quote:

quote:Originally posted by daneboy

Thanks for the info. I'll try to find the diagram. I just want to use the generator while boondocking, so no transfer switch is necessary. It's a real pain to break out the heavy 50 amp cord then add two adapters so it can be pluged into a 15/20 amp outlet or generator.
Thanks,
Jerry

Easier to use one of these short 30 AMP adapters than fighting those 50 AMP cords...

They're sold at Campers World, and a lot of other RV Parts Suppliers

Garin1 · 03-27-2006, 05:17 PM

There is not a jumper in the thirty to fifty adapter. If there were there would be a direct short and the breaker would trip. The adapter brings one of the 50 amp hot legs to a dead position so all you end up with is one hot,one neutral and one ground at 30 amps.

jpbcny · 03-28-2006, 12:11 AM

Quote:

quote:Originally posted by Garin1

There is not a jumper in the thirty to fifty adapter. If there were there would be a direct short and the breaker would trip. The adapter brings one of the 50 amp hot legs to a dead position so all you end up with is one hot,one neutral and one ground at 30 amps.

The 30 AMP to 50 AMP adapter that I have pictured below, is jumpered from the single 30 AMP Hot Leg to BOTH of the 50 AMP Hot Legs, sharing the one 30 AMP Feed to both Buss Bars in the RV Power Center. I don't have a second A/C, but there are several circuits on each Buss Bar, and all work while plugged into the 30 AMP Adapter. I have "Rang-Out" the adapter with a Meter, and I can assure you it is jumpered to BOTH Hot Legs.

JP

daneboy · 03-28-2006, 04:25 AM

JP,
Thanks, I haven't seen the short jumper pictured before. That's my solution and I'm going to buy one. Then we won't need to drag out the monster cord every time.
Jerry

JH Sechelt · 03-28-2006, 03:06 PM

Hi Jerry,

Here is what we ended up doing.
We purchased a 25 foot 30 amp extension cord and a 50 amp marinco female connector. I cut the female end off of the extension cord and put the 50 amp connetor on. You have to add a jumper wire from the Hot ( black wire connector) to the (red wire connector) in the 50 amp plug. If you don't add the jumper only half of the circuits work in your trailer.
It does the same thing as pluging the 50 amp to 30 amp adaptor to your 50 amp monster cord. in that case the jumper is in the 50 to 30 amp adaptor. It seems to work great here in our driveway, and You don't have to man handle the 50 amp monster cord or use a bunch of adaptors.

Take care
John & Dawn

Garin1 · 03-28-2006, 07:46 PM

Jp, I stand corrected on the wiring of the adapter. It raises the hackles on the back of my neck though to realize that with this setup there is such a great potential for damage. Correct me If I am wrong again but, if you are supplying power from one leg of a thirty amp plug to TWO legs of a fifty amp rv the potential for overload is very high. Not everyone is alert to how easy it is to overload a circuit. I call this the checkbook mentality,IE: I still have checks,I must have money. Should someone attempt to use the full power of the rv with this setup there could be serious damage (should the park breaker not trip).

jpbcny · 03-28-2006, 10:57 PM

Quote:

quote:Originally posted by Garin1

Jp, I stand corrected on the wiring of the adapter. It raises the hackles on the back of my neck though to realize that with this setup there is such a great potential for damage. Correct me If I am wrong again but, if you are supplying power from one leg of a thirty amp plug to TWO legs of a fifty amp rv the potential for overload is very high. Not everyone is alert to how easy it is to overload a circuit. I call this the checkbook mentality,IE: I still have checks,I must have money. Should someone attempt to use the full power of the rv with this setup there could be serious damage (should the park breaker not trip).

You will only be able to get 30 AMPS Max between the two circuits, its no different than staying in a CG with only 30 AMP Service. Obviously if you try to Run everything possible in the RV, that you can with 50 AMP Service you will be tripping the 30 AMP Breaker (unless in a rare situation it is defective).These adapters are for when you don't want to pull out the 50 AMP cord, either because there is only 30 AMP Service available, or you don't need to run 2 A/Cs, or an A/C and washer/dryer at the same time. In my personal situation, 30 AMPs is sufficient for my RV as I don't have a 2nd A/C, or a washer/dryer, or any other add on appliances. It's just a way to be able to run anything in your RV, whether the are on either circuit (Just not all at the same time).

JP

rvfirefighter · 03-29-2006, 12:17 AM

Wiring a long 30 amp extension cord for a 50 amp plug is using a smaller wire than in than 50 amp cord. This will create more heat in the wire and more heat and damage to the appliances if you try to run too much stuff off 30 amp service. It is no different than a 30 to 50 amp pigtail, just longer.
The only time, as some have stated, you need 50 amp service is when you try to run 2nd A/C, Washer and Dryer, Hairdryer, Electric Heater, Electric Hotwater, etc. at the same time.

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