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Old 06-04-2013, 09:46 PM   #15
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This is Not a True Statement

Quote:
Originally Posted by adonh View Post
As I understand it, A 50 amp RV power source through a 50 amp RV power cord is designed to provide 2 lines of 110 volt power to a designated 50 amp RV.

.
You may be confused with 220 volts.
A 50 amp receptacle has three wires: a neutral, a hot, and a ground.
Just like your 30 amp receptacle.
Just like your 15 amp receptacle.

15, 30, and 50 are all 120 volt AC.
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Old 06-04-2013, 09:52 PM   #16
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Quote:
Originally Posted by Alumaholic View Post
You may be confused with 220 volts.
A 50 amp receptacle has three wires: a neutral, a hot, and a ground.
Just like your 30 amp receptacle.
Just like your 15 amp receptacle.

15, 30, and 50 are all 120 volt AC.
Actually, a 50 amp RV service is 240 VAC, has four wires, 2 legs hot at 120 VAC, one neutral wire, and one ground wire.

Inside the RV breaker panel, it is wired and used as two different 120 VAC circuits, and nothing in the conventional RV like an Airstream, runs on 240 VAC. I understand some of the larger motorhomes do have some 240 VAC appliances.
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Old 06-04-2013, 10:21 PM   #17
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Quote:
Originally Posted by Alumaholic View Post
You may be confused with 220 volts.
A 50 amp receptacle has three wires: a neutral, a hot, and a ground.
Just like your 30 amp receptacle.
Just like your 15 amp receptacle.

15, 30, and 50 are all 120 volt AC.
Depends on what you are talking about. I have never seen a 50 amp 120v outlet in a campground.
The 50 amp 4 wire outlet that the campground provides is 240v.
The 30 amp 3 wire outlet that the campground provides is 120v.
When you connect the adapter (adapting the 50 amp outlet so that your 30 amp chord will work) you plug your 30 amp rated 120v plug in to one leg (hot wire) of that 240v 50 amp outlet. The amperage of the campground's circuit is not changed by the adapter, except it is limited by the smaller 30 amp rated wire in your trailer's electric chord. The voltage is not changed, you only use a portion of it. So through an adapter you are feeding your trailer with a 50 amp 120v circuit. This is no problem as long as your trailer's 30 amp main breaker functions properly.
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Old 06-04-2013, 11:11 PM   #18
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Steve H and Warn have a grasp on this voltage thing. I am aware that it can be confusing but look at it this way and it will be easier to understand. In the 50 amp receptacle there are 2 prongs that have 120 volts but are opposite polarity, so if they are supplied to 240 volt equipment they provide the necessary 240 volts. In this case the neutral (white) is not energized. When only 120 volts are needed as in an airstream only one of the power legs is used and the neutral completes the circuit back to the source. The ground (green) is only there incase of a fault and should never be energized under normal conditions. In 50 amp RV's though 240 volts are available it is not supplied to any 240 volt equipment but each leg of the power providing 120 volts each feed two separate bus bars and each bus provides 120 volts for the equipment. When using a 50 amp to 30 amp adapter you connect to only one of the hot legs of the 50 amp supply thus bringing your chord in contact with only 120 volts. It is safe.
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Old 06-05-2013, 12:10 AM   #19
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ok i'm confused. i thought that campground 50 amp plugs provided two 25 amp/120 volt hot wires, one neutral and one ground.

do the adapters in fact use one of the hots thereby providing 25 amps or do they combine the two hots and provide 50 amps?
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Old 06-05-2013, 12:24 AM   #20
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Originally Posted by markdoane View Post
I doubt this description is right. The cord itself should be 3-wires, one of which is the ground.

Which begs the question posed by the original poster. If you plug a 10 gauge cord, rated for 30 amps, into a receptacle rated 50 amps, you are exceeding the rating of the cord.

This will normally be OK, because if the amps exceed the 30 amp rating the 30 amp main breaker in the trailer should trip.

However, the cable itself is not protected. If there is a high resistance short or loose connection within the plug, dogbone adapter, or cable itself it could overheat.

Risk is low, but you you inspect the cord and adapter each time you use it and discard if it shows any sign of overheating.
Markdoane: As a safety manager, I applaud your post, pointing out the potential of the cable overheating.

I'm a relative newbie, but every place I have stayed with 50 amp service has also had a 30 amp plug. MY moho had the 50 amp option from the factory but I end up plugged into 30 amps in many places that don't have 50 service, but have not had a problem yet. I have not used, nor will I try to run both a/c's on 30 amps, would probably pop the breaker. Almost anything else is okay.

The other issue is power quality: rv parks are reported to have "flaky" power and many people recommend surge/sag protectors. If voltage goes low with your a/c running the low voltage could damage the a/c unit, and a sudden surge could burn out any electronics that are plugged in, like a microwave, radio, computer, etc.
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Old 06-05-2013, 05:54 AM   #21
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Unless the adapter has 30 amp fuses then it is not only a bad idea to use it but violates numerous Nat Electrical Code sections. The circuit breaker in this case is a 50 amp breaker, with a cord rated at 30 amps. The circuit breaker will not trip until 50 amps is exceeded, A previous poster pointed out that the trailers main would prevent damage to the trailer, this is true, but the trailers main breaker is downstream of the un-protected cord. If an adapter is on the market that has internal fuses then go for it, otherwise Bad Idea.
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Old 06-05-2013, 05:59 AM   #22
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ok i'm confused. i thought that campground 50 amp plugs provided two 25 amp/120 volt hot wires, one neutral and one ground.

do the adapters in fact use one of the hots thereby providing 25 amps or do they combine the two hots and provide 50 amps?
Ricky, the 50 amp receptacle provides two 50 amp legs, for a total of 100 amps at 120v. The power cord is #6 AWG - 3 wires plus ground.

The adapter uses just one of the hot legs, and is capable of 50 amps. The 50 amps is limited to 30 amps only by the main breaker in your trailer.
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Old 06-05-2013, 07:10 AM   #23
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Originally Posted by Hodum View Post
In the 50 amp receptacle there are 2 prongs that have 120 volts but are opposite polarity, so if they are supplied to 240 volt equipment they provide the necessary 240 volts. In this case the neutral (white) is not energized. When only 120 volts are needed as in an airstream only one of the power legs is used and the neutral completes the circuit back to the source. The ground (green) is only there incase of a fault and should never be energized under normal conditions. In 50 amp RV's though 240 volts are available it is not supplied to any 240 volt equipment but each leg of the power providing 120 volts each feed two separate bus bars and each bus provides 120 volts for the equipment. When using a 50 amp to 30 amp adapter you connect to only one of the hot legs of the 50 amp supply thus bringing your chord in contact with only 120 volts. It is safe.
This is accurate, folks, and the best description I've read here. I did not want to get into explaining how the two 120 VAC legs make a 240 VAC circuit, did not want to use the word polarity, or especially the word phase, (really more accurate because we are talking about AC)because that brings up a whole other argument.

Anyway, Hodum's description is accurate.
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Old 06-05-2013, 07:17 AM   #24
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ok, thanks Mark.
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Old 06-05-2013, 07:56 AM   #25
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Thank you all. I should have studied my physics in college more extensively!
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Old 06-05-2013, 11:14 AM   #26
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Another thing to consider when using the adapters: I have seen the 30 amp (120v) single pole breakers that are GFCI. Not all of them, but some. I have never seen a 50 amp two pole (240v) breaker. When you use those adapters in wet weather be cautious how you place your trailer cord. If the connection point is in a puddle or the chord is wet and you walk through the puddle or touch the chord, it could be shocking!

Is there an adapter with a GFCI built in?
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Old 06-06-2013, 10:57 AM   #27
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There are some RV boxes that are equipped with 50 amp 240 volt double pole GFCI breakers. I have had one for several years. They are more expensive but GFCI is the safest thing going whether single pole or double pole. They are designed to detect the slightest amount of current flow going to ground for any reason and trip the breaker immediately. In case there is a short circuit to the metal of your trailer the ground wire should carry the current back to the breaker box and the breaker would trip from an overload condition. In case the ground wire had lost connection for any reason the trailer would be setting as a electrical death trap waiting for someone connected to the ground to touch it. However if there is GFCI protection it will sense the fault as soon as someone touches the trailer and trip the breaker before damage is done. GFCI measures the amount of current (in 1/1000's of an amp) that is being supplied by the hot leg and balances it against the current returning on the neutral leg and trips the breaker when the slightest imbalance occurs. Safety is paramount.
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