This is going to sound like a dumb question to most of you, but I know almost nothing about electricity. My 85 Regal is a 30 amp coach. The main cord to shore power has three wires, black, white, and light green. There is no bare copper ground wire. Which is power,which is neutral, which is ground? Any idea of what size they are? I'm running a line from the 50 amp box the Regal is plugged into (using a 50 to 30 cord) about 85 feet and am trying to figure out how to do it and what size wire I need. I have a 30 amp receptacle and box to use once I get to the new location and was just going to use half of the 50 amp box. It's actually wired with 2 30amp breakers directly from the main 200 amp panel in the house. Should I use 8-2 with ground like the guy at Lowe's said? Or something else+

Black is hot; white is neutral; green is ground. Typically, #12 wire for 20 amps; #10 wire for 30 amps; #8 for 40, and #6 for 50 amps.
Distance factors into wire size, and 85 feet is on the far limits; I'd use #8 for a 30 amp service, esp since cost of wire is not much more.
"50 amp" service typically has two 120v "wires" which is 220v together; either one is, of course, 120v; a 50 amp service will use a single neutral and a single ground wire with the two hot wires. The two 30-amp breakers in your box is technically a 60-amp service. Your 30 amp adapter is bypassing one of the two hot wires coming from the box.
Use one of the two 30 amp breakers; use #8, and two-#8-w/ground is okay, but I'd use all three #8 if it's readily available. Direct burial wire is probably available, and is a good solution if you're going underground.
It's not a dumb question; electricity is simple to the experienced, but difficult -and perhaps deadly- to the novice.

Jim, what electric devices are you going to operate when plugged in to your new box?

I would set it up for 50 amp service as long as you are doing it. You next unit may be wired for 50 amp. I mean you may change motor homes sometime in the future.

It is easier to plug a 30 amp into a 50 vs. tring to run a 50 amp coach on a 30amp circuit.

"I would set it up for 50 amp service as long as you are doing it."

50 amp service requires: #6 wire (significant more cost); a 4th (red) wire; 50 amp receptacle; possibly a larger box; and you must change the two single-pole 30 amp breakers for one double-pole {or a linked pair} 50 amp breaker @ $60. Even if you don't have a safety problem the city will zap you (pun!) if they notice it. Other than that, it is a good idea; the days of 30 amp coach service are dead.

Bill, I'm just going to plug the Regal into it. We just finished a building to house it and keep it our of the weather but it 85' away from the house. We would love to convert our 30 amp service to 50 amps so we could run both air conditioners at the same time without running the generator, but changing to 50 amps seems pretty expensive, new boxes, new transfer switch, etc. At my age and income level, this will probably be our last motor home.

quote:

Originally posted by humbojb:
We would love to convert our 30 amp service to 50 amps so we could run both air conditioners at the same time without running the generator, but changing to 50 amps seems pretty expensive, new boxes, new transfer switch, etc.

There is a device or two on the market that will cycle your air conditioners alternately, so that only one runs at a time. I made my own a while back when I had a 30 amp coach.

It will not provide any more BTUs of cooling, but will make the Barth more evenly cooled.

bill, where would I look for one of the switching devices you mentioned?

Thanks for all the info. I ran 8-3 plus ground to a 30 amp receptacle. I had planned to use one of the three #8 wires for ground but it was too big to fit into the ground terminal along with the grounding wire for the box. So I used the bare copper wire for ground. All seems to work fine. Plugged the Barth in and my volt meter measures 123 volts. I am curious about the amps. But my volt meter says don't try to measure anything more than 20 amps. Is there another way to see if I'm getting 30 amps all the way to the motor home?

quote:

Originally posted by humbojb:
Plugged the Barth in and my volt meter measures 123 volts. I am curious about the amps. But my volt meter says don't try to measure anything more than 20 amps. Is there another way to see if I'm getting 30 amps all the way to the motor home?

Harbor Freight sells a clamp on ammeter that reads AC amp draw. It is often on sale. However, if you are showing an honest 123 volts with either the air conditioner or microwave operating, you are fine. The rule of thumb is to have less than a 5% voltage drop from source to coach. 8 wire gives you a good margin.

I just now saw your query on the two air conditioner on one 30 amp device. I can't remember where I saw it, but a dealer should know something. I made mine out of a timer that controlled two circuits. Turned off one air cond and turned on the other one every few minute. The timer I had was light duty, so I used it to control relays to switch the heavy current. A slow-turning motor could use cams to operate two microswitches, too. I measured the bleed down time of the compressors to set the time. Air conditioners do not like to start against a pressure head. I used a clamp on ammeter for this, but observing voltage drop would do it, too.