Frame Ground/Chassis Wire - Page 3 - Fiberglass RV


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Old 04-28-2013, 10:56 AM   #29
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Originally Posted by felix2 View Post
Keep in mind that with 120V, there is a difference between a grounded neutral, and an equipment grounding conductor (EGC). A neutral is the return path of the electrical circuit, which is earthed at the neutral bus (which also carries the circuit ground conductor); the purpose of an EGC is to ground the equipment/housing/junction box. You would not mix the neutral and EGC. The EGC merely provides an earthing means for the device's housing, in case it should somehow become energized.

Isn't electrical fun?
To add more "fun" the equipment ground does not have to be "earthed". For example, when powering a trailer from a Honda inverter generator, you still have an equipment ground (it is the metal frame of the generator) but no earth connection. In fact, you also have no bond of the neutral to the earth. While completely safe, that can present a problem for EMS systems or most surge guards such as the Progressive EMS-HW30C Surge Protector that I have on my trailer. They will assume there is an open ground because of the method the manufacturer used to detect the ground connection. A 3 lamp tester will also show a fault.

One of the ground conductor's primary purposes is to trip a fuse or breaker if there is a fault to any metal in the home (or RV). This is the reason for bonding the frame & other metal to the ground conductor.
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Old 04-28-2013, 11:21 AM   #30
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The primary purpose of the equipment grounding conductor is to assure a low impedance path to ground and facilitate the tripping of the overcurrent device as quickly as possible The equipment grounding conductor is not designed to be a current carrying conductor except under certain select conditions (Fault) In certain instances the code requires metallic raceways as well as an equipment grounding conductor to assure a low impedance path "redundant" (Coronary Care Units) . Secondly bonding and grounding are not the same term . Swimming pool equipment is bonded but not necessarily grounded .Rebar ,railings ,ladders drains etc are bonded . The grounding of your trailer frame limits the voltage to ground for safety reasons.. The biggest problem I have seen is when people use grounded and grounding as meaning the same thing "THEY ARE NOT" They use equipment grounds as current carrying conductors or neutral conductors as equipment grounding conductor or my favorite "Just tie all the neutrals together they all go to the same spot in the breaker panel (See festoon lighting in the NEC)
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Old 04-28-2013, 12:27 PM   #31
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The primary purpose of the equipment grounding conductor is to assure a low impedance path to ground and facilitate the tripping of the overcurrent device as quickly as possible The equipment grounding conductor is not designed to be a current carrying conductor except under certain select conditions (Fault) In certain instances the code requires metallic raceways as well as an equipment grounding conductor to assure a low impedance path "redundant" (Coronary Care Units) . Secondly bonding and grounding are not the same term . Swimming pool equipment is bonded but not necessarily grounded .Rebar ,railings ,ladders drains etc are bonded . The grounding of your trailer frame limits the voltage to ground for safety reasons.. The biggest problem I have seen is when people use grounded and grounding as meaning the same thing "THEY ARE NOT" They use equipment grounds as current carrying conductors or neutral conductors as equipment grounding conductor or my favorite "Just tie all the neutrals together they all go to the same spot in the breaker panel (See festoon lighting in the NEC)
I don't believe the first paragraph is exactly correct. Safety grounding was required long before GFI devices were invented. The purpose of the safety ground is keep the ground (earth) at the same electrical potential as any metal on the electrical device. Thus eliminating shock hazards.
GFI (Ground Fault Interrupt) measures the current differential between the hot and neutral lines, If they aren't the same the hot connection is removed. Safety ground and GFI are entirely separate.

Use of safety ground (including trailer frames) for current carrying conductors is not a good idea.

I'm not sure what your statement about tying all the neutrals together means. I'm guessing that somebody is including safety ground with neutral. In that case, tying safety ground to neutral in any location other than at the distribution panel is asking for trouble in the form of shock hazards.
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Old 04-28-2013, 03:55 PM   #32
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Tripping an over current protective device has nothing to do with GFCIs. Steve is correct - if a hot side connection or insulation faults to any metal that is accessible, it is critical that there is a low impedance path that will force the tripping of the breaker or fuse, weather or not there is a GFCI protecting the circuit. The Equipment Ground Conductor (the bare or green non current carrying wire) is there for that purpose.

Prior to the 1960's wiring was 2 wire - a hot & neutral. During the early 60's a undersized ground wire was added & used to protect the metal boxes, but not carried through to the receptacle. The purpose was to protect users from a shock from the metal receptacle covers by tripping the circuit's fuse or breaker if there was a fault to the metal box.

I believe it was the 1965 code that required a full sized ground (for 15 & 20 amp circuits). Grounding (3 pole) receptacles were required with the 1975 code, although they were available before that time and often installed. My code history notes are on loan, so I may be off a code or two.
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Old 04-28-2013, 04:32 PM   #33
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Thanks Jon for reading what I wrote

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Originally Posted by Jon Vermilye View Post
Tripping an over current protective device has nothing to do with GFCIs. Steve is correct - if a hot side connection or insulation faults to any metal that is accessible, it is critical that there is a low impedance path that will force the tripping of the breaker or fuse, weather or not there is a GFCI protecting the circuit. The Equipment Ground Conductor (the bare or green non current carrying wire) is there for that purpose.

Prior to the 1960's wiring was 2 wire - a hot & neutral. During the early 60's a undersized ground wire was added & used to protect the metal boxes, but not carried through to the receptacle. The purpose was to protect users from a shock from the metal receptacle covers by tripping the circuit's fuse or breaker if there was a fault to the metal box.

I believe it was the 1965 code that required a full sized ground (for 15 & 20 amp circuits). Grounding (3 pole) receptacles were required with the 1975 code, although they were available before that time and often installed. My code history notes are on loan, so I may be off a code or two.
Jon I think you are correct when I started day school we were using the 1965 NEC and romex was required to have a full size equipment ground . Previously 14-2 romex had a # 16 equipment grounding conductor which often suffered mechanical damage and the loss of ground . Secondly as you stated a GFCI is not an overcurrent device nor is it designed to be used as one (. Take a short piece of wire and short out a GFCI receptacle ,(Hot to Neutral) the fuse or breaker trips not the GFCI) .Lastly often time people without a understanding of electricity will find a junction box with two or more circuits and do not keep the neutrals separate ( There all white so just splice them all together method) causing parallel neutral conductors or you can shut off a breaker to the circuit you are working on and discover there is neutral current from another circuit. An open neutral is just as deadly as a Hot conductor. The old neutral (grounded conductor) rule is pick it up first ,lay it down last I know grounded outlets were required in 1971 and the GFCI requirements started around 1973
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Old 04-28-2013, 04:49 PM   #34
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Originally Posted by Jon Vermilye View Post
Tripping an over current protective device has nothing to do with GFCIs. Steve is correct - if a hot side connection or insulation faults to any metal that is accessible, it is critical that there is a low impedance path that will force the tripping of the breaker or fuse, weather or not there is a GFCI protecting the circuit. The Equipment Ground Conductor (the bare or green non current carrying wire) is there for that purpose.

Prior to the 1960's wiring was 2 wire - a hot & neutral. During the early 60's a undersized ground wire was added & used to protect the metal boxes, but not carried through to the receptacle. The purpose was to protect users from a shock from the metal receptacle covers by tripping the circuit's fuse or breaker if there was a fault to the metal box.

I believe it was the 1965 code that required a full sized ground (for 15 & 20 amp circuits). Grounding (3 pole) receptacles were required with the 1975 code, although they were available before that time and often installed. My code history notes are on loan, so I may be off a code or two.

Tripping a circuit breaker or blowing a fuse has nothing to do with 3 wire ground. The third wire is there to keep the metal, whether it outlet box or the side of your toaster, at the same potential as the earth. You CANNOT increase the speed at which an over current device trips without changing the over current device.
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Old 04-28-2013, 04:59 PM   #35
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Yes it does. If there was no ground wire, a fault to a metal receptacle box would make the box live to a near by ground or the neutral. A metal cover attached to the strap of the receptacle would make the cover at the same potential as the box. Again, this would be a shock hazard. The purpose of the ground wire is to cause a large amount of fault current that will trip the fuse or breaker.

There are examples where the ground is not at the earth potential - I mentioned a Honda inverter generator as an example in a previous post, In fact, there are examples here that point out some advantages on not grounding.

I suggest spending some time reading Article 250 in the NEC and at the Grounding vs Bonding section of the Mike Holt forum.
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Old 04-28-2013, 05:44 PM   #36
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I'm with Jon on this one, hot to case opens the breaker. Also, you don't want anything you can touch carrying current. (I think Steve mentioned that). If it is, then there can be a voltage present. Raz
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