110V electric short

[BroncoAl]

I have an electrical problem. I have a short in my trailer in the 110V system. The other day my son went out to the trailer which I keep plugged in the house to look for something. He was in his bare feet and when he touched the handle to a storage compartment he got a slight shock. I turned off both receptacles for the wall outlets and have figured out that is where the short is. I unplugged the trailer for now. How do I go about measuring the current on the outside of the trailer so I don't have to use my kid as a guinea pig? Where should I look first to resolve the problem?

[vermilye]

Correct. The bonding should take place at the home or campground service entrance, not in the trailer's panel.

[Seattle_Lion]

Actually, don't you mean that the trailer should have the same ground as the electric panel? If the trailer was wired correctly, I would expect that the ground (green) from the shore power line would go to the frame of the trailer. I would also assume that the neutral (white) would NOT be grounded in the trailer. As I understand it, the neutral should only be grounded at the main breaker panel to avoid any ground/neutral current loops.

[vermilye]

Seattle Lion wrote:

smkettner wrote:
Still, get the outlet tester. Still could be reverse polarity as there is no neutral ground bond in the RV.

If there is no neutral/ground bond in the RV, then GFI's wouldn't work. I think neutral in the camper should be connected at the power center to the incoming ground (not earth, the green ground wire on the 30 amp cord). A problem with this conductor going into your camper will let all AC "float", which can be hazardous if some stuff in the camper is not using polarized plugs. A quick way to test this is to look for voltage between neutral (white) and ground (green) at various points in your power chain.

This issue is one reason why it is important to check shore AC before plugging in.

It is important that there is no neutral/ground bond in the trailer. Again, the only place the neutral should be bonded to the ground is at the campground service entrance. While some metered pedestals are treated as a service entrance and the bond is at the pedestal, it should never be bonded in the trailer.

Why? If you bond the neutral to the trailer's ground you have a parallel circuit. The neutral current will split, part on the neutral wire & the remainder on the ground wire. Since the ground is (or should be) bonded to the trailer's frame, and in the campground, all the metal in buildings, water & gas plumbing, etc they are now carrying part of the neutral current. Believe it or not, you could receive a shock disconnecting your water hose from the campground connection if you have a ground/neutral bond in the trailer!

As to a GFCI, it does not need a ground to work properly. A GFI or GFCI monitors the current in the hot wire & the neutral. If they differ by more than 5ma, it shuts the circuit down. Usually the fault that causes the difference is to ground, but if it was to another hot or a different neutral it would still shut down. Code allows a GFCI receptacle to be used to replace an old 2 wire receptacle without connecting the ground pin connection - it still provides fault to ground protection (see Article 250.130(C) of the 2011 NEC).

Lastly, in a properly wired system there can & usually will be a small voltage between the neutral & hot. The neutral will be carrying current. If it is, there must be a voltage drop across the length of the neutral wire (Ohm's law). Since the ground is not carrying current, even though they are both connected to the same point at the service entrance, at the load end there can (and under load, should) be a difference.

[Seattle_Lion]

smkettner wrote:
Still, get the outlet tester. Still could be reverse polarity as there is no neutral ground bond in the RV.

If there is no neutral/ground bond in the RV, then GFI's wouldn't work. I think neutral in the camper should be connected at the power center to the incoming ground (not earth, the green ground wire on the 30 amp cord). A problem with this conductor going into your camper will let all AC "float", which can be hazardous if some stuff in the camper is not using polarized plugs. A quick way to test this is to look for voltage between neutral (white) and ground (green) at various points in your power chain.

This issue is one reason why it is important to check shore AC before plugging in.

[Nvr2loud]

vermilye wrote:

Nvr2loud wrote:

JesLookin wrote:

Nvr2loud wrote:

24rules wrote:
I agree but if the trailer is properly grounded there would be no stray voltage to be felt since the frame is part of the ground

I just did some work on a melted neutral bar in my trailer and discovered that there is no ground to frame on the 120 volt side, only on the 12 volt side. The ground from shore power goes to the grounding bar and all the outlets ground wires go to that bar. The bar is isolated and there is no ground wire to frame anywhere that I can find, is this unusual? I can clearly see where the 12 volt ground goes to frame.

There should not be a connection between the neutral & ground in your trailer. The neutral & ground should be connected at the campground power supply. The trailer is an accessory plugged into the campground power. Just as there is no connection between ground & neutral for any appliance you plug in at home, such as heater, etc...

I know that already, my question was about the ground wire from shore power, in my trailer that ground wire DOES NOT connect to the trailer frame at any spot. The shore ground wire (120 VAC on 30 amp connection) simply goes to a ground bar and that bar is isolated from the trailer frame. My concern is creating a ground through a person from the trailer to ground.

Check in your converter. If it is wired to code, there should be a #6 wire connecting the converter ground to the trailer frame.

You can use an ohm meter to check - it there really is no connection between the ground buss & the trailer frame, there should be. Without one, you have a shock hazard waiting to happen.

I know there isn't a connection, I just thought there should be one and wondered if I'm right or not. It is already strange to me that the neutral and the ground are not bonded together in a trailer, so therefore I thought perhaps there was some reason to avoid the 120 volt grounds from bonding to the trailer frame (since it is the 12 volt ground already)

[Nvr2loud]

john&bet wrote:

Nvr2loud wrote:

john&bet wrote:

wittmeba wrote:
john&bet,

Not trying to argue but who put the label on your problem as a "short"? I think the term "short" is used when describing an electrical condition that may not be fully understood or easy to explain.

I would agree with BB_TX as a short is a condition where a line is directly touching a neutral or ground. That almost (if not always) should trip a breaker. It is different than a situation where the line and neutral are swapped (happens with 2 wire extension cords) which is likely what the OP has indicated.

This condition seems to appear weekly or more on this forum.

The plugin tester is $5.00 at Walmart.

I did. I have a $300. tester and know how to use it. This is what makes trouble shooting hard from a distance. Have a good day.

I don't care if you have a $300.00 tester and 'know how to use it' you still did not have a short.

There was a dead short between the to hot wires of a 50 amp service in the romex in the trailer that tripped a 50 amp 2 pole pedestal c/b and would not trip a 30 amp shore c/b plain and simple that is a short. That does not take a meter to find. You just have to start digging into the trailer. Enough said. Thank you and have a good day.

Now I agree with you....

You stated in your first post that you could have a short without tripping a circuit breaker or fuse... You are actually tripping a circuit breaker at the pedestal. You failed to identify that fact until this post. The short between the two 'hot' wires of a 240volt 50 amp service connection would instantly trip or fry a breaker, and that is exactly what you had happen. I disagreed completely until you stated where the short was and the tripping of the pedestal breaker.

[john_bet]

Nvr2loud wrote:

john&bet wrote:

wittmeba wrote:
john&bet,

Not trying to argue but who put the label on your problem as a "short"? I think the term "short" is used when describing an electrical condition that may not be fully understood or easy to explain.

I would agree with BB_TX as a short is a condition where a line is directly touching a neutral or ground. That almost (if not always) should trip a breaker. It is different than a situation where the line and neutral are swapped (happens with 2 wire extension cords) which is likely what the OP has indicated.

This condition seems to appear weekly or more on this forum.

The plugin tester is $5.00 at Walmart.

I did. I have a $300. tester and know how to use it. This is what makes trouble shooting hard from a distance. Have a good day.

I don't care if you have a $300.00 tester and 'know how to use it' you still did not have a short.

There was a dead short between the to hot wires of a 50 amp service in the romex in the trailer that tripped a 50 amp 2 pole pedestal c/b and would not trip a 30 amp shore c/b plain and simple that is a short. That does not take a meter to find. You just have to start digging into the trailer. Enough said. Thank you and have a good day.

[vermilye]

Nvr2loud wrote:

JesLookin wrote:

Nvr2loud wrote:

24rules wrote:
I agree but if the trailer is properly grounded there would be no stray voltage to be felt since the frame is part of the ground

I just did some work on a melted neutral bar in my trailer and discovered that there is no ground to frame on the 120 volt side, only on the 12 volt side. The ground from shore power goes to the grounding bar and all the outlets ground wires go to that bar. The bar is isolated and there is no ground wire to frame anywhere that I can find, is this unusual? I can clearly see where the 12 volt ground goes to frame.

There should not be a connection between the neutral & ground in your trailer. The neutral & ground should be connected at the campground power supply. The trailer is an accessory plugged into the campground power. Just as there is no connection between ground & neutral for any appliance you plug in at home, such as heater, etc...

I know that already, my question was about the ground wire from shore power, in my trailer that ground wire DOES NOT connect to the trailer frame at any spot. The shore ground wire (120 VAC on 30 amp connection) simply goes to a ground bar and that bar is isolated from the trailer frame. My concern is creating a ground through a person from the trailer to ground.

Check in your converter. If it is wired to code, there should be a #6 wire connecting the converter ground to the trailer frame.

You can use an ohm meter to check - it there really is no connection between the ground buss & the trailer frame, there should be. Without one, you have a shock hazard waiting to happen.

[Nvr2loud]

john&bet wrote:

wittmeba wrote:
john&bet,

Not trying to argue but who put the label on your problem as a "short"? I think the term "short" is used when describing an electrical condition that may not be fully understood or easy to explain.

I would agree with BB_TX as a short is a condition where a line is directly touching a neutral or ground. That almost (if not always) should trip a breaker. It is different than a situation where the line and neutral are swapped (happens with 2 wire extension cords) which is likely what the OP has indicated.

This condition seems to appear weekly or more on this forum.

The plugin tester is $5.00 at Walmart.

I did. I have a $300. tester and know how to use it. This is what makes trouble shooting hard from a distance. Have a good day.

I don't care if you have a $300.00 tester and 'know how to use it' you still did not have a short.

[Nvr2loud]

JesLookin wrote:

Nvr2loud wrote:

24rules wrote:
I agree but if the trailer is properly grounded there would be no stray voltage to be felt since the frame is part of the ground

I just did some work on a melted neutral bar in my trailer and discovered that there is no ground to frame on the 120 volt side, only on the 12 volt side. The ground from shore power goes to the grounding bar and all the outlets ground wires go to that bar. The bar is isolated and there is no ground wire to frame anywhere that I can find, is this unusual? I can clearly see where the 12 volt ground goes to frame.

There should not be a connection between the neutral & ground in your trailer. The neutral & ground should be connected at the campground power supply. The trailer is an accessory plugged into the campground power. Just as there is no connection between ground & neutral for any appliance you plug in at home, such as heater, etc...

I know that already, my question was about the ground wire from shore power, in my trailer that ground wire DOES NOT connect to the trailer frame at any spot. The shore ground wire (120 VAC on 30 amp connection) simply goes to a ground bar and that bar is isolated from the trailer frame. My concern is creating a ground through a person from the trailer to ground.

[vermilye]

BroncoAl wrote:
It's plugged into a 20A GFI breaker on the front porch with an adapter to the 30A cord. How do I go about trouble shooting the problem if there is no obvious problem?

If it doesn't trip a GFCI & you are no longer getting a shock from the trailer I wouldn't worry about it. It could be a very high resistance fault, for example capacitive coupling, etc that doesn't produce enough current to cause a problem. If you still want to chase it down, measure the ground current while switching off each breaker.

[john_bet]

wittmeba wrote:
john&bet,

Not trying to argue but who put the label on your problem as a "short"? I think the term "short" is used when describing an electrical condition that may not be fully understood or easy to explain.

I would agree with BB_TX as a short is a condition where a line is directly touching a neutral or ground. That almost (if not always) should trip a breaker. It is different than a situation where the line and neutral are swapped (happens with 2 wire extension cords) which is likely what the OP has indicated.

This condition seems to appear weekly or more on this forum.

The plugin tester is $5.00 at Walmart.

I did. I have a $300. tester and know how to use it. This is what makes trouble shooting hard from a distance. Have a good day.

[JesLookin]

Nvr2loud wrote:

24rules wrote:
I agree but if the trailer is properly grounded there would be no stray voltage to be felt since the frame is part of the ground

I just did some work on a melted neutral bar in my trailer and discovered that there is no ground to frame on the 120 volt side, only on the 12 volt side. The ground from shore power goes to the grounding bar and all the outlets ground wires go to that bar. The bar is isolated and there is no ground wire to frame anywhere that I can find, is this unusual? I can clearly see where the 12 volt ground goes to frame.

There should not be a connection between the neutral & ground in your trailer. The neutral & ground should be connected at the campground power supply. The trailer is an accessory plugged into the campground power. Just as there is no connection between ground & neutral for any appliance you plug in at home, such as heater, etc...

[Nvr2loud]

24rules wrote:
I agree but if the trailer is properly grounded there would be no stray voltage to be felt since the frame is part of the ground

I just did some work on a melted neutral bar in my trailer and discovered that there is no ground to frame on the 120 volt side, only on the 12 volt side. The ground from shore power goes to the grounding bar and all the outlets ground wires go to that bar. The bar is isolated and there is no ground wire to frame anywhere that I can find, is this unusual? I can clearly see where the 12 volt ground goes to frame.