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Old 06-11-2013, 11:09 AM   #29
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Okay, so do the individual 120 AC ground wires in receptacles, attach to the frame/skin?
No.

The body/frame/skin is used for a ground for 12 v., not 120 v. There are usually 3 wires for 120: hot (black), common (white) and bare or green (ground). Sometimes other colors are used, especially in residential or commercial uses, but mostly it goes this way. The ground for 120 goes back to the pedestal.

If you grounded 120 v. to the trailer, a short could make touching it very interesting. What a way to wake up!

By the way, common is sometimes misidentified as ground, but it is not.

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Old 06-11-2013, 12:17 PM   #30
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Thanks,
So then the ground wires in the receptacles just get wired in series. Correct?
Also I see conflicting ideas on grounding the 120 volt distribution/breaker box. By this thread I am realizing that there is no 120 ground on the trailer, just rely on the shore power ground.
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Old 06-11-2013, 12:55 PM   #31
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Thanks,
So then the ground wires in the receptacles just get wired in series. Correct?

Tony
No again. I only think of that distinction when talking about light bulbs and batteries in series or parallel.

Each conductor is wired to a receptacle and continues to the next one (unless it is the last, of course). Each conductor is either connected together with a pigtail to the receptacle, or the receptacle links it all together. If the receptacle fails and the wires all attach to it, depending how that was done, you may or may not lose the rest of the circuit, but probably won't.

Series and parallel circuits are confusing— Series and parallel circuits - Wikipedia, the free encyclopedia

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Old 06-12-2013, 09:19 AM   #32
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I think I've got it straight in my head now. Any pictures perchance?
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Old 02-02-2014, 11:01 AM   #33
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Revisiting this thread. I used metal boxes on my 120 circuit. If the ground wire touches the box (a likely occurrence) am I in trouble? Should I have used the original Bakelite boxes and or plastic?
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Old 02-02-2014, 11:27 AM   #34
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The ground wire (copper or green) must be attached to the metal boxes using some type of connector designed for this type of connection. This is a safety issue.

If you would have used plastic boxes (non conducting), it would not have been necessary to attach the ground.
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Old 02-02-2014, 11:57 AM   #35
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That is the way I set it up but that then makes it grouded to the skin which a previous poster said was a danger.
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Old 02-02-2014, 12:50 PM   #36
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Ground wire getting hot?????

The skin of the coach SHOULD be grounded to the earth ground provided by the power company. There are three wires in the 120 volt AC 30 amp Circuit providing power to the coach.
Black=Hot (obviously not connected to earth ground)
White= Neutral (NOT connected or bonded to earth ground inside the coach)
Copper or Green=Earth Ground (connected or bonded to the Earth Ground Plane provided by the Utility Company and in some if not all systems by a ground rod driven deep into the earth) This wire in most cases is attached to the frame or skin of the coach close to where the power panel is located.
Larger coaches may be wired for 240 volt and will have an additional hot leg. Usually Red.
The Earth ground system on your coach is a different animal than the Common/Ground system. While they BOTH are connected to the skin/frame of the coach.
Earth ground is for SAFETY on the 120 volt AC side of the system.
Common/Ground is the RETURN side of the 12 volt DC system. Most, if not all 12 volt devices have only 1 wire for the POSITIVE side of the circuit. The negative side is connected thru the skin/frame of the coach. Thus the reason for the negative terminal of the battery to be connected in some way to the skin/frame of the coach.
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Old 02-02-2014, 02:01 PM   #37
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The ground wire is grounded to the ground terminal on the outlets. In doing that, the screws that attach the outlet to the box, ground the outlet to the box. If the box is metal, it in turn grounds it to the shell. The white wire must not be grounded in the breaker box, but must be on it's own buss with the rest of the white wires. Then connected to the white wire in the shore power cord. If the white wire is grounded in the trailer breaker box, like in house power, the ground fault breakers will not work in the trailer.
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Old 02-02-2014, 02:28 PM   #38
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There are no 240 volt coaches!
50 amp service is simply 2 110 volt feeds..... they share a bonded or common neutral and a ground.
Wired as follows... 2 hot wires
A neutral 2x the awg as the x and y hot and a ground.
Technically should you remove the common neutral you will introduce 240 volts to the coach... destroying any 110 volt devices.

30 amp service is a hot a neutral (common) and a ground.
The ground is bonded to the shell the hot (black) goes to all hot sides and neutral (white) goes to the neutral sides.
The real danger here I'd if the hot and neutral legs ate reversed the metal shell of the Airstream becomes energised. Should you have wet feet and are standing on grass dirt or anything wet and touch the shell.... poof you are dead as you just completed a hot path to earth and took 110-120 volts and 30+ direct amps through the heart muscle
All your 110 receptacles news to be grounded to your breaker box then box to the service entrance cable to plug. You can also ground each plug to the shell but shances are you are using wire with a ground.... and it always best to have everything pointed to a common ground point.
If your ground wire is getting hot you have a leak somewhere seeking ground. This is a potential safety hazard
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Old 02-02-2014, 04:52 PM   #39
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That is the way I set it up but that then makes it grouded to the skin which a previous poster said was a danger.
You will have to educate yourself, then sort through the posts and figure our who knows what they are talking about and who does not. There are some of both in this thread.
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Old 02-02-2014, 06:04 PM   #40
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All modern AS products are shell grounded to the ground wire which goes directly to your power source.

Make no mistake the shell is bonded to ground.
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Old 02-08-2014, 06:02 PM   #41
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There was a question about using a metal box to replace a plastic one. They use the plastic ones because it saves labor—no need to ground to the box saves seconds. I think the plastic ones are cheaper too. I prefer metal because I'm used to them and know their quirks, but either can work fine.

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Old 02-08-2014, 08:48 PM   #42
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Ground wire getting hot?????

Here is my take on A/C wiring in a travel trailer. If all old work is done according to customary color standards, every device will have a black "hot" wire, a white common "neutral" and a green or bare safety ground.

The safety ground will connect to the trailer frame and body, and EVERY piece of conductive material that might be exposed to either the neutral OR the hot wire should be grounded.

All three, hot, neutral, and ground, should be totally isolated from the other with the safety being provided by the ground wire from the shore power, generator, or inverter providing the power.

The problem with a trailer is that either the hot wire or the common might be capable of electrocuting a person under certain circumstances if a trailer is not grounded properly. This ground can provided either through a properly wired shore ground in a plug, or via a copper ground stake driven into the earth.

Back a few decades ago, the third safety wire was not universal in all residential power, which will explain why early trailers had a ground lug provision so people might not get electrocuted.
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