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Old 03-30-2016, 09:53 AM   #11
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I'm no electrician, but tying the two out-of-phase hot legs together seems wrong to me. Can someone help me wrap my head around this?
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Old 03-30-2016, 09:54 AM   #12
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Third Bama's post. See the diagram because a picture is worth more than a thousand words in this case. http://www.forestriverforums.com/forums/attachment.php?attachmentid=88430&d=1442072654

If you are not familiar with electrical wiring please consult with an electrician. Incorrect wiring can damage the RV and create a deadly shock hazard.

A standard 20 amp and 30amp female outlet has one hot (120V Black), one neutral (White), and one ground (Green). Verify this at the outlet with volt meter before proceeding. See the linked diagram above for the correct meter readings.

A 50 amp RV service has 2 separate hots (one Black 120v, one Red 120v), 1 neutral (white), and 1 ground (Green). The 2 hot feeds are 2 completely separate 120volt currents in the RV. The RV is not 240volts. The black side typically feeds everything but the second AC and a washer/dryer if so equipped. These are typically wired to the red hot side.

To go from 20 amp or 30amp to 50 amp, in the 50 amp female plug connect the ground wire (green) to the "G" terminal, neutral (white) wire to the "W" terminal, and the hot (Black) wire and to the "Y" terminal, then make a jumper from the "Y" terminal to the "X" terminal. After wiring, check with a voltage meter (reference the diagram) before connecting to the RV.

If you are not familiar with electrical wiring please consult with an electrician. Incorrect wiring can damage the RV and create a deadly shock hazard.
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Old 03-30-2016, 10:03 AM   #13
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Originally Posted by DadOfTwo View Post
I'm no electrician, but tying the two out-of-phase hot legs together seems wrong to me. Can someone help me wrap my head around this?

The 2 hots legs are not out of phase. An RV service is not a 240 volt service. It is 2 completely separate 120volt feeds. The 2 hot legs in the plug can be connected together. This is what an adapter does.
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Old 03-30-2016, 11:30 AM   #14
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I'm no electrician, but tying the two out-of-phase hot legs together seems wrong to me. Can someone help me wrap my head around this?
It's not tying 2 phases together it's putting a single phase on both 120 volt leg inputs to the camper. The camper doesn't care as both individual 120 volt busses will have 120 volts on it. Phasing is not utilized by anything in the camper. Yes, if plugged directly to a 50 amp receptacle without an adapter there will one phase on one bus and another phase on the other bus. There will be 50 amps of power to each of those busses. When a 50 to 30 amp adapter is used there will be 30 amps total to both buses.
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Old 03-30-2016, 11:36 AM   #15
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Quote:
Originally Posted by DadOfTwo View Post
I'm no electrician, but tying the two out-of-phase hot legs together seems wrong to me. Can someone help me wrap my head around this?
Quote:
Originally Posted by bubbles View Post
It's not tying 2 phases together it's putting a single phase on both 120 volt leg inputs to the camper. The camper doesn't care as both individual 120 volt busses will have 120 volts on it. Phasing is not utilized by anything in the camper. Yes, if plugged directly to a 50 amp receptacle without an adapter there will one phase on one bus and another phase on the other bus. There will be 50 amps of power to each of those busses. When a 50 to 30 amp adapter is used there will be 30 amps total to both buses.
This picture may also help show how bubbles and others are using a jumper to share the 30 amps between both the L1 and L2 in their adapter.

The wiring schematic for the the 50 amp female to 30 amp male adapter is the one on the far right:

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Old 03-30-2016, 12:34 PM   #16
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Quote:
Originally Posted by bubbles View Post
It's not tying 2 phases together it's putting a single phase on both 120 volt leg inputs to the camper. The camper doesn't care as both individual 120 volt busses will have 120 volts on it. Phasing is not utilized by anything in the camper. Yes, if plugged directly to a 50 amp receptacle without an adapter there will one phase on one bus and another phase on the other bus. There will be 50 amps of power to each of those busses. When a 50 to 30 amp adapter is used there will be 30 amps total to both buses.
120/240 Single phase IS NOT TWO phases! Single phase three wire systems are also known as an Edison system, split-phase or center-tapped neutral. This is the most common residential service in North America. Line 1 to neutral and Line 2 to neutral are used to power 120 volt lighting and plug loads. Line 1 to Line 2 is used to power 240 volt single phase loads.
Yes, the two high legs are 180 degrees out of phase with respect to one another and one might consider this as two phases. But whether you run a motor off 120 volts or 240 volts, it is still a single phase motor. As an electrician I have met electricians that don't understand this!
BTW When you are obtaining your power from a 120vac 30amp receptacle, using the adapter to supply your 50 amp service, you are supply power to both side from one 30 amp circuit.
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Old 03-30-2016, 05:18 PM   #17
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Is the 50 amp wiring on RVs split phase 240 volts?

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I'm no electrician, but tying the two out-of-phase hot legs together seems wrong to me. Can someone help me wrap my head around this?
I'm just as confused as you are, DadOfTwo. I guess we are both used to wiring homes, which have 240 volt split phase circuits. There are two hot sides with 240 volts between them and each has 120 volts to the common neutral. (The neutral never carries more current than either hot side alone, and if you are drawing the same current from both hot sides, no current is carried by the neutral.)

Given that 50 amp RV service has 4 wires, I have always assumed an RV is wired like our houses. Split phase would give you 50 amps times 240 volts or 12,000 watts.

If you have split phase 240 volts, tying the two hot sides together, as proposed by others, will either blow the circuit breaker or blow up the wire if the circuit breaker fails. In other words, this is a bad idea.

The wiring that others are describing would share the neutral line between two separate hot circuits, and hence be limited to the 50 amp capacity of that neutral line. In other words, it would only produce 50 x 120 or 6,000 watts. That seems pretty odd, given that a lot of RVs have 10,000 watt generators – that means they would have more generator power than shore power.

The safe way to do this, which would work safely with both wiring systems, is to hook one of the hot sides (either blade on the side, red or black) and the neutral (blade in the middle, white) of the 50 amp circuit to the hot (black) and neutral (white), respectively, of the 30 amp circuit. This will give 30 amps safely and not blow fuses.

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Old 03-30-2016, 05:29 PM   #18
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Gordon, you are not tying together the L1 and L2 hot lines coming FROM the service when using the adapter. You are only using the L1, and then jumping/sharing it over to the L2 going INTO the RV.

There is no L2 line coming out of a 30 amp service. See the schematic on post #15.

---------------------------------------------------

On a 50 amp split phase service, there are two lines with a common shared neutral that come FROM the service INTO the RV. However the bus inside the RV stays separate, with the 120 volt L1 providing power to certain things, and then the 120 volt L2 providing power to others. The do share a common neutral, but the load balances between the L1 and L2 sides, with the only the indifference being carried by the neutral.

Since the RV has a 50 amp double pole breaker that ties basically two 50 amp breakers together (100 amp total), then if one side (either the L1 or the L2), or the common neutral carries more than 50 amps, it trips both side together so the neutral can't burn up.

This allows the L1 to provide 6000 watts and also the L2 to provide 6000 watts...for a total of 12000 watts.

Hold on and I will get you a link to explain it better.
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Old 03-30-2016, 05:35 PM   #19
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This link explains it better:

Electrical Tutorial - Chapter 3 - 30 Amp versus 50 Amp
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Old 03-30-2016, 05:46 PM   #20
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Here is a diagram of the circuit panel inside a 50 amp RV, so you can see how the L1 and L2 provide power:

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