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Old 10-25-2012, 01:15 PM   #15
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Every electrical box I have seen has both the neutral and ground hooked to the same bus inside the breaker box. There is no other way to do it if you use a standard box. You do need separate neutral and ground wires leading away from the box to the various circuits in the trailer. There should also be a ground between the box and the trailer. It is not a bad idea to have a separate ground stake outside the trailer as well.

I think AS turned a standard box on my trailer into a 120V box by backfeeding through a 30 AMP breaker and then jumpering the two hot rails together so both sets of breakers work.

Perry
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Old 10-25-2012, 01:39 PM   #16
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Every electrical box I have seen has both the neutral and ground hooked to the same bus inside the breaker box.
Perry
This is untrue. The only electrical box where the gound and neutral are bonded is the MAIN SERVICE PANEL, not a subpanel. Subpanels always have separate ground and neutral. Most of the panels you buy at Home Depot or Lowes have a removable bonding connection between the ground and neutral bus.

You're supposed to read the directions and understand whether you are installing a main panel or a subpanel. If it's a subpanel, you need to buy a grounding bus and install it in the panel. There are always holes and a location for the ground bar.

The main panel in a trailer is really a subpanel, and via the power cord plugs into an outlet. The box where you plug in the power cord is the main panel and that is where the ground and neutral are bonded.

Any other method is incorrect and unsafe. Please if you don't understand the rules, call a professional.
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Old 10-25-2012, 01:50 PM   #17
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This is untrue. The only electrical box where the gound and neutral are bonded is the MAIN SERVICE PANEL, not a subpanel. Subpanels always have separate ground and neutral. Most of the panels you buy at Home Depot or Lowes have a removable bonding connection between the ground and neutral bus.

You're supposed to read the directions and understand whether you are installing a main panel or a subpanel. If it's a subpanel, you need to buy a grounding bus and install it in the panel. There are always holes and a location for the ground bar.

The main panel in a trailer is really a subpanel, and via the power cord plugs into an outlet. The box where you plug in the power cord is the main panel and that is where the ground and neutral are bonded.

Any other method is incorrect and unsafe. Please if you don't understand the rules, call a professional.
X2 X2... Well said!

This is an easy fix, just get the neutral busbar that can be isolated from the metal panel and you will be done.
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Old 10-25-2012, 01:50 PM   #18
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Typically a box you get a places like Home Depot is set up to use as a Main Distribution Box. Not as a Sub Panel.
The panel in your trailer is considered a Sub Panel.
Depending on the use there is a long green screw called a Bonding Screw that is used to BOND the neutral buss to the cabinet. In the case of a Main Panel, this screw would be inserted thru a hole in the neutral buss and screwed into the chassis or metal box. These panels have provisions for a ground buss as well, which by the method of mounting bonds the ground buss to the cabinet or metal box.
In the case if a Sub panel, the neutral is not bonded.
There are a number if sights on the web that give specifics on RV wiring. Both the 120 volt side as well as the 12 volt side.
Don't confuse the AC ground circuit with the DC ground circuit. They are 2 different animals.
The AC ground is for SAFETY.
The DC ground is a method used to save wire. Where the chassis of the trailer is used for the return path on most DC circuits. It was mislabeled years ago in the Auto industry and has carried over to the RV industry. It should have been labeled "Common", since it is the negative side of the DC circuits and is "Common" to all DC components in the RV. There are typically no switching devices on the Common side of the circuit.
I would strongly recommend that you do your homework on this subject. If not totally competent about what you are doing. Hire someone who is. Your LIFE could depend on it.
There is a web site: dasplace.net/RVWiring/wiring.hotmail
Check it out.
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Old 10-25-2012, 01:57 PM   #19
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Here is another web site. With better info: www.myrv.us/electric/
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Old 10-25-2012, 02:22 PM   #20
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Ok so why is it unsafe for the neutral and ground to be connected in a sub panel?

Here is a link I found on what the problem is.

http://inspectapedia.com/electric/El...utral_Lost.htm

I need to look at my shop wiring. Looks like I need to separate the blocks and also put in a ground stake.

Perry
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Old 10-25-2012, 02:32 PM   #21
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You don't understand the basics of electrical safety. Please stop before you burn down your trailer.
Also, you should have bought a box with mains breakers, not a mains lug box. You are in way over your head.
YOU ARE WIRING AN RV.........NOT A HOUSE! There Are distinct differences tags you should be aware of before you proceed!!!!!!!!
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Old 10-25-2012, 02:42 PM   #22
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I think it would help if we talk about why what he did is wrong and educate everyone in the process. I am learning things as well. We all start out at incompetence and move up from there. Why not propose an an alternate schematic as well. I am going to do what he is attempting to do and I want to understand why one way is right and the other is wrong. If you know why something is the way it is then you are more likely to do it right the next time. Let's help him fix it right.

Perry
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Old 10-25-2012, 03:15 PM   #23
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Perry,

The problem with bonding the neutral and ground together in the trailer electrical panel is that it can lead to stray voltage on the shell.

A condition inherent to 120/240v wiring is "unbalanced load," that is, the situation where the load on the two "hot" legs isn't equal. Under these conditions, current flows in the neutral leg, equal in magnitude to the difference between the current flow in each of the hot legs. With RVs a similar situation results when a 30a-to-50a "dogbone" is used, because then the neutral leg carries the sum of the current flow in each of the hot legs (since they're in phase and not really two different legs as would be the case when plugged into a 120/240v, 50a shore power receptacle).

The large current flow in the neutral results in there being some voltage drop between the bonding point and the trailer electrical panel. This can be several volts. If the neutral is bonded to the trailer frame, then a person might get a shock from contacting the trailer frame and the ground at the same time.

While the ground connection does help with this in practice it will carry part of the neutral current and therefore have some amount of voltage drop itself. Ultimately this can create stray voltage for others in the campground.

It is a common fallacy that the neutral and ground wires are interchangeable among DIY electricians. Perhaps this is because, as late as 1980, ranges and dryers were typically grounded through the "neutral" conductor -- the continuation of an emergency measure adopted in 1943 to address the copper shortage during WWII. Or perhaps it is because, in farm and home wiring, ground conductors were undersized until about 1970, so that many electricians would use a neutral wire instead for grounding because it was larger.

In any case, the practice is dangerous, and should be avoided.

As an aside, the U.S. practice of bonding at both the transformer and the service entrance panel poses its own set of problems. A few countries omit one of the bonding points.
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Old 10-25-2012, 03:20 PM   #24
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Every electrical box I have seen has both the neutral and ground hooked to the same bus inside the breaker box. There is no other way to do it if you use a standard box.
Most breaker boxes intended for residential use only come with a neutral bus but accept a ground bar that is purchased separately. Most big-box home improvement stores sell ground bars for the breaker boxes they carry.
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Old 10-25-2012, 03:24 PM   #25
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Ok so why is it unsafe for the neutral and ground to be connected in a sub panel?

Here is a link I found on what the problem is.

Electric system neutral wire loss leads to shocked homeowner

I need to look at my shop wiring. Looks like I need to separate the blocks and also put in a ground stake.
It depends.

If your shop is fed from the electrical panel in the house, you should have a four-wire feeder. I believe that under most codes the ground stake is then optional although that may vary regionally or depending on year of construction.

If your shop is fed from its own meter, then the neutral should be bonded, and you need a ground stake or some other grounding electrode.
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Old 10-25-2012, 03:27 PM   #26
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Why would I need two breakers? There is a 50 amp breaker right outside. The original box that I replaced did not have a main breaker either.
In general a main breaker is not required on a sub-panel if there are six or fewer breaker handles in the panel.

I don't believe that a main breaker is important, safety wise, in this situation.
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Old 10-25-2012, 03:30 PM   #27
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I haven't used a 50 amp service at a campground, but I think you will find that only half of your panel will be hot. Since I believe it is wired thru a single breaker and not a double pole breaker, which is typically how the 240 volt wiring is done in your home.
The neutral and ground should not be connected together. The neutral should not be bonded to the trailer body. Only the ground should be bonded to the trailer body.
TG

It's supposed to be wired as a 240/120v circuit with a double pole breaker, and it usually is, and in most areas that's the way the code says it has to be.

I have heard of various dodgy wiring approaches, such as feeding both sides of a 50a receptacle from a single pole breaker, but have never encountered them in my travels.
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Old 10-25-2012, 03:53 PM   #28
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Well, yesterday I thought I was doing OK. The electrical system was done and the next "to do" was being started. I put up a photo to show the new electrical system and my friend TOP sent a note to recheck the ground/neutral connection. Sure enough I had fallen into the same trap of using a standard Circuit breaker box and that suckered me into connecting the neutral and ground to a common buss in that box. This discussion sums it all up...I have the new buss installed. So far not shocked.
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