Aluminum Camper Forum

Hi everyone. I'm Mike Sokol, a technology writer for a number of RV publications including RVtravel.com.  You can read my latest RV Electricity column at http://rvtravel.com/whats-all-this-electrical-ground-stuff-about/ and here's my first monthly newsletter at http://rvtravel.com/electricity1/

Feel free to email any questions about RV electrical hookups or safety to mike@noshockzone.org. And I'm glad to answer questions on this forum as well, as long as something sends me a message that my help is needed.

Let's play safe out there...

Mike Sokol

Quote from: charliem on April 29, 2017, 04:17:01 PM

BTW, in the world I come from anything above 0dBm is high power 

How about +4 dBu 

BTW: I might have a sponsor that will allow me do a few seminars about RV electrical safety and hookups at campgrounds on the mid-atlantic coast. Do you guys have any rallies or meets this summer or fall? I'm in Maryland and normally do seminars as far south as SC and as far north as NY. And I go as far west as Ohio and Indiana. Any suggestions?   

Quote from: charliem on April 29, 2017, 01:26:29 PM

Quote from: jmsokol on April 29, 2017, 01:03:03 PM
Actually, every dogbone adapter you see with 15/20 to 50 amp converter plugs does a jumper between the two hot legs on the 50-amp side, and connects it to the single hot leg on the 15/20-amp side.
Mike Sokol
The No~Shock~Zone

Mike,

I know you really didn't mean what you said. A jumper between the two hot legs on the 50A side would be very exciting....for a millisecond or so. The dogbone adapters connect ONE 50A hot to the 15/20/30A socket.

Actually, I did mean what I said, but let's make sure I'm being clear about what I'm saying. On a 15-amp male to 30-amp female adapter there's one-to-one connections between the hot, neutral and ground contacts. That is, Hot-to-Hot, Neutral-to-Neutral, and Ground-to-Ground. On a 30-amp male to 50-amp female adapter there's a slightly different connection setup. While there's a Ground-to-Ground connection and Neutral-to-Neutral connection from the 30-amp male plug to 50-amp female outlet, there's also a Hot-to-Hot-to-Hot connection from the 30-amp male plug to the 50-amp female outlet. That is, both hot legs of the 50-amp outlet are indeed bonded together and connected to the single hot leg of the 30-amp plug. That being the case, a single 20-amp male plug to 50-amp female outlet does have the two hot legs bonded together on the 50-amp outlet side. Of course, you can't bond the two hot legs together on the incoming power side as that would be a spectacular short as you noted.

I think why there's confusion is that I'm an EE and always talk about power from the source to the load. That is, I start on the end that plugs into the pedestal or home outlet and finish with the end you plug your RV into. So while I will call something a 15 to 30 amp dog-bone adapter, I have noticed that a lot of RV owners talk about adapters the opposite way. That is, you'll call the same thing a 30 to 15 amp adapter to plug your 30-amp RV into a 15-amp outlet in your home. Hard for me to get out of that habit after 50 years of going from power source to load.

Also note that it's hard for me to call any of this an outlet. In the NEC it's referred to as a receptacle, NOT an outlet, even though outlet makes more sense.

So please sound out if what I'm saying is confusing. I'm trying to be as exact as I can while still using as much layman slang as possible. If you need more clarification you'll need to wait until I get back from Paris next week. I have a bunch of diagrams on my home computer I can post later.

Quote from: FastEddieB on April 29, 2017, 08:46:07 AM
That would also energize both sides of the 50A breaker. If I went this way I could either disconnect the hot leads out from the 50A breaker or just leave the 50A breaker off and mark it INOP. I had already thought about marking the 30A outlet "20A SERVICE ONLY".

Actually, every dogbone adapter you see with 15/20 to 50 amp converter plugs does a jumper between the two hot legs on the 50-amp side, and connects it to the single hot leg on the 15/20-amp side. So you can make the jumper yourself and save someone from needing an adapter. Same for the 30-amp outlet adapters. Of course, you'll still have only 20 amps available, but if you go over the limit the circuit breaker will trip, so no big deal.

QuoteI forgot to check the gauge of the cable in the underground run. From the photo, it looks to me like the runs to the outlets in the cover is 12GA, and the cable coming into the box is clearly larger - 10 GA? I will check next time up.

If it's 10 gauge that's great since that will reduce the voltage drop on 125 of wire significantly. In fact I generally oversize the wire gauge on any run that's going to be over 100 ft, and even for 50 ft runs.

QuoteAs an aside, I also painted the ground wire a much brighter green to avoid possible confusion.

Just be as obvious as you can be. We generally use green PCV electrical tape.

Mike Sokol
The No~Shock~Zone

Quote from: FastEddieB on April 21, 2017, 08:36:38 AM
2) It appears as though the 30A outlet will be "hot" if I throw the breaker. I know more than a 30A draw will pop the breaker at the temp pole, but otherwise is it feasible to just plug my 30A cable into that? I'm hoping the gauge of the wire and relatively short (125') run may allow us to run the air conditioning. If not we can always power up our generator in the heat of the day.

Yes, the way this is wired will allow the 30-amp outlet to be powered up, but only with 20 amperes of current available. That's not dangerous and not even a code violation as long as you make it with a +20-amp service" sticker in some locations. The upstream 20-amp circuit breaker will protect the 12-gauge wire run from over-current, so that's perfectly safe. However, 125 ft of wire is a really long run (code calculations are based on 100 ft), so it's doubtful you'll be able to start an air conditioner on that circuit. You'll want to listen carefully when starting the HVAC to make sure it's not going into locked-rotor mode (humming but not starting up) since you can destroy an HVAC compressor pretty quickly with undervoltage.

Mike Sokol
No~Shock~Zone