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Old 11-03-2011, 04:52 PM   #1
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Electrical...the more I try to understand it, the more confused I become

I have what appears to be a 30 amp electrical outlet on the side of my home that I want to use to keep my RV charged up.

Looking at my home's breaker box, every 30 amp breaker I have is 2 pole. When I put a meter on the outlet's black and ground, I get a reading of 125v. Black and white also reads 125v. White and ground reads zero.

I was told by an electrician I know that the above readings indicate a single pole breaker. Then I go to this page RV Electric under the link to "outlet testing". According to this, my readings indicate 2 pole, and is considered "RV friendly".

RV 30 amp service is supposed to be single pole, no?

Someone or something I'm reading is incorrect. What can y'all add to this state of confusion I appear to be in?

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Old 11-03-2011, 05:00 PM   #2
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30A service is 120v with a single pole breaker as there is only one hot line.

A 2 pole breaker is used for 240v service.

Do both terminals of the 30A two pole breaker have wires connected to them?

You need to verify what is actually wired.

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Old 11-03-2011, 05:07 PM   #3
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Good to ask before proceeding.....if you go to the section on 30A service, you'll see it specifies a single 30A breaker. And the explanation for how both ends of the connection are wired, if you plan on checking. I would.

Note: If you do not feel completely comfortable opening up and working in a hot breaker panel. Don't. Find someone who does.

Find the breaker assocaiated with the this outlet and mark it. I'd keep it switched Off when not in use since it is outside.

I usually check anything I personally have not installed for correct wiring and tightness of terminations. Loose connections can heat up and cause problems.

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Old 11-03-2011, 05:14 PM   #4
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There is 30 amp 220 outlet, and there is 30 amp 110 outlet they are not the same configuration. A dryer outlet is a 30 amp 220. An RV uses a 30 amp 110. That means a hot lead going to one phase of your house hold 2 phase power and a single breaker. In 30 amp 110 volt rv recepticle there is 1 hot lead typically black, one neutral should be white, and one ground either green or a bare. All is the same on 220 except you also have a red wire oposite phaze from the black and a 2 pole breaker.
Check the wire size at the outlet. Is it 10 gauge wire or 6 gauge wire and how many conductiors do you have? You may have to trace out the wires to find out what's happening. I've seen some really goofy electrical stuff in my years as a custom home builder.
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Old 11-03-2011, 05:55 PM   #5
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I think the wording on that website is confusing. He's referring to 30 amp (one hot lead) as 2-pole, and he refers to 50 amp (two hot leads) as three pole.

So, normally, a 30 amp RV wired socket would only have one single pole breaker. If you don't have any single pole 30 amp breakers, it's possible that used to be a 240v AC outlet and the wiring has been changed (but not the breaker). Start turning off breakers until you figure out which one is feeding that outlet, then see if you can figure out where the other half of the breaker is going to. You might even want to open up the outlet box (with the breaker off) and see if there's an extra wire in there not going to anything. Or take the cover off the breaker box and see if that extra wire is going to the neutral bar.

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Old 11-03-2011, 06:14 PM   #6
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If it is a 2 pole breaker, it is 240 volts. You will read, 120 v on either side to the ground, but hot to hot is 240 v.

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Old 11-03-2011, 06:39 PM   #7
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Your readings indicate a single pole circuit. It may be wired to a 15 or 20 amp breaker. As the other folks have said, I'd first figure out which breaker it's on, and turn it off. Then you can find out if there is anything else on the circuit, and you can open up the outlet and see what size wire was used. If the wire size is sufficient, and its the only outlet on the circuit, you can check the connections, and replace the 15A or 20A with a single phase 30A one for your RV.
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Old 11-03-2011, 06:52 PM   #8
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Something you are reading is indeed incorrect... however The voltage readings you are seeing do indicate "RV SAFE"

Recommendation.. Open the main breaker box inside the RV, turn off ALL breakers, epically the mains.

now plug in to that outlet.. Measure the voltage between the Main breaker's screw (IT WILL BE HOT) and the white wire bus. Should be in the 120-125 range plus or minus a bit
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Old 11-03-2011, 07:37 PM   #9
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You are trying to convert a older (pre-1996) appliance outlet to RV operation.
Read the Appliance Service section of his site which addresses part of this confusion. He actually is using the corrrect context and you will see this in other documentation also.
Nema Plug and Receptacle configurations
NEMA Plug & Receptacle Configurations Reference Chart (Straight Blade)
It's the reference point that is creating the confusion. "2 Pole" in the NEMA context relates to North-South (Hot & Nuetral) pole windings at the generating source.

From his Appliance section:

Converting the OLD APPLIANCE (10-30 or 10-50) service to a 30-amp 120-volt 2 pole 3 wire RV service is simple. Remove the Double pole breaker and replace it with a Single pole 30-amp breaker. This service requires 3 wires 1 Black (Hot lead) 1 White (Neutral) and 1 Ground. One of the hot wires will have to be made into a Ground wire. Remove the insulation or use green tape to identify it for future reference. Install a TT-30R receptacle and its ready to go.

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Old 11-04-2011, 03:45 AM   #10
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Super info in these replies. Thanks so much! We are headed out for the weekend, but I will get back on this next week.

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