To ground or not to ground...

1. NO you need 4 conductors from the service 300 feet away. (hot, hot, neutral & GROUND) 2. YES the only place that neutrals and grounds are tied together is at the service. 3. Supplemental grounding is fine as long as the grounding conductor is sized for the service. Your situation a #4 would work.
"There are no continuous metallic paths bonded to the grounding system in both boxes, therefore there are no parallel neutral paths running between them. " I have not the foggiest idea what you mean by this.

in article S1n_d.256721$0u.189666@fed1read04, SQLit at snipped-for-privacy@cox.net wrote on 3/17/05 3:56 PM:
There is no 4th conductor. Essientially, what I have is a "mobile home" setup. The service drop is designed for a mobile home and it feeds the subpanel with the two HOTS and NEUTRAL.
If my neutral and ground are isolated in the subpanel, wouldn't I HAVE to have a supplemental ground there for bonding my plumbing, satellite, telephone etc.?

in article S1n_d.256721$0u.189666@fed1read04, SQLit at snipped-for-privacy@cox.net wrote on 3/17/05 3:56 PM:
For my situation reference:
Which states that this is an acceptable wiring practice under the given conditions.

Sorry, but you're screwed. You must absolutely have 4 wires. If the neutral gound link were not present in the meter base, that would make the meter base the code violation instead of your 3 wire circuit.. Both the grounded and grounding conductor must have separate continuity paths back to the initial ground
Unless someone can point me to a code exception for trailers.

Yes. Yes. Yes.
My lake cabin is located aproximately 300 feet from my service drop. At the meter I have a 200 AMP main service panel with disconnect. It is grounded to an 8' copper rod in the ground. The Neutral buss and ground are bonded in case.
From this box I am running a three wire feeder (two 4/0 ungrounded hots and one 2/0 neutral) to a 200 AMP subpanel on the cabin itself.
There are no continous metallic paths bonded to the grounding system in both boxes, therefore there are no parallel neutral paths running between them.
The lake cabin has interior copper plumbing attached to a PVC water main.
Questions:
1. Do I need a secondary grounding rod at the cabin 2. If so, do I isolate the neutral from the ground in the subpanel? 2. Do I need to bond the plumbing to the neutral buss or the ground in the subpanel?
Thanks in advance.

Actually i believe there is a provision in the NEC that requires you to have a second earth grounding means at the other panel since both buildings are not connected in any other shape or form other than your subpanel feeders. {bonding a must for gas & water pipes if so connected}
How much Electrical energy does your trailer need? do you have any 220vac appliances in it ?
If not: Rather than dig up and place another Ground Plate or Rod ~ change one of the Hot underground conductors = attach it to your Neutral Bus on Both Panels., transfer also the smaller gage conductor to your Ground Bonding Buss on both Panels., and bond every outlet device or box throughout the trailer or it would all be for naught.
I don't know if this method is all up to code (you'd onlt have 110VAC/100A) but it is better than a free range of 2Hot & 1 Neutral with no ground path at the offset location.
NOTE: If the offset is a permanent Post Installation (where you plug your RV into) it behooves you to add an additional earth ground for that subpanel., this is not an appliance we're talking about but an albeit separate building or structure. It should have an adequate earth ground.
Also Note: I have not researched Trailer Park Installations for you.
* That webpage on the matter can be quite elusive if you do not determine your specific situation };-)
Roy ~ E.E.Technician

Yes. Yes. Yes.
aproximately 300 feet from my service drop. =A0 At the meter I have a 200 AMP main service panel with disconnect. It is grounded to an 8' copper rod in the ground. =A0 The Neutral buss and ground are bonded in case. From this box I am running a three wire feeder (two 4/0 ungrounded hots and one 2/0 neutral) to a 200 AMP subpanel on the cabin itself. There are no continous metallic paths bonded to the grounding system in both boxes, therefore there are no parallel neutral paths running between them. The lake cabin has interior copper plumbing attached to a PVC water main. Questions: 1. Do I need a secondary grounding rod at the cabin 2. If so, do I isolate the neutral from the ground in the subpanel? 2. Do I need to bond the plumbing to the neutral buss or the ground in the subpanel? Thanks in advance.
by all means just isolate the neutral from the ground buss and add your earth/bonding. it's not much of a science anymore };-) you just need the bonding ground and you cannot have continuity between the two busses.

My replies are in line.
tar> My lake cabin is located aproximately 300 feet from my service drop. At If the building is supplied with electricity by anything except a single branch circuit it must have a grounding electrode system. That's right. No matter how many or few conductors are in the feeder or multiple branch circuits there must be a grounding electrode system at each building! In the case of a 120/240 volt feeder run on three conductors you must not isolate the neutral buss from the panel enclosure cabinet. The neutral Buss must be bonded to the cabinet and the grounding electrode conductor must be terminated to the neutral buss bar. If you isolated the neutral conductor from the enclosure cabinet you would be using the earth as the grounding electrode conductor which the code specifically forbids. Yes both plumbing systems must be bonded to the bonded neutral buss bar but since the underground piping is nonmetallic you can bond both piping systems to the building disconnecting means enclosure at the closest convenient point on the two piping systems. The conductor used for bonding need only be as large as the Equipment Grounding Conductor that the code has identified for the Over Current Protective Device that is protecting the feeder to the building. Your welcome -- Tom H

CAUTION: You must not make a ground circuit connection (to neutral) ~ (nor jumper) at the load side (or Subpanel)., Only at the Service Panel as suggested if Art. 250 applies ~ Art.250.24(A)(5) =AEoy

quoted from link ...." Section 250-24(a), Two or More Buildings or Structures ......"
......" With the 1999 edition, the NEC no longer requires one to reground the neutral conductor at the second building."..................
I must have missed the other building. I was sure he said a service feeding one building. The service is not considered a building.

The NEC covering the answer below is 250.32. This was cited in a reference by tarin in another post: You want a low resistance path from the grounded outlets, plumbing, etc. at the cabin to the neutral, so shorts from the hot to a grounded object will have a high current and trip the breaker. It is permissible to run a ground wire from the service panel at the meter and not bond the neutral and ground at the cabin, but this would produce a higher fault resistance.

1. The stated question is for a cabin, not a trailer 2. If you don't know if your method is up to code why do you post it?

in article d1f53o$gnd$ snipped-for-privacy@news.chatlink.com, Bud at snipped-for-privacy@isp.com wrote on 3/18/05 11:44 AM:
not bond the neutral and ground at the cabin, but this would produce a higher fault resistance.
Run the ground wire from the service panel to a grounding electrode OR to the subpanel??

From: snipped-for-privacy@isp.com (Bud) 1. The stated question is for a cabin, not a trailer 2. If you don't know if your method is up to code why do you post it?
Answer: because it's a practical safe soltion.The OP mentioned it was more of a Traler than a Cabin.
Roy Q.T. wrote: Actually i believe there is a provision in the NEC that requires you to have a second earth grounding means at the other panel since both buildings are not connected in any other shape or form other than your subpanel feeders. {bonding a must for gas & water pipes if so connected} How much Electrical energy does your trailer need? do you have any 220vac appliances in it ?
* If not: Rather than dig up and place another Ground Plate or Rod ~ change one of the Hot underground conductors = attach it to your Neutral Bus on Both Panels., transfer also the smaller gage conductor to your Ground Bonding Buss on both Panels., and bond every outlet device or box throughout the trailer or it would all be for naught. I don't know if this method is all up to code (you'd only have 110VAC/100A) but it is better than a free range of 2Hot & 1 Neutral with no ground path at the offset location. NOTE: If the offset is a permanent Post Installation (where you plug your RV into) it behooves you to add an additional earth ground for that subpanel., this is not an appliance we're talking about but an albeit separate building or structure. It should have an adequate earth ground. Also Note: I have not researched Trailer Park Installations for you. * That webpage on the matter can be quite elusive if you do not determine your specific situation };-) Roy ~ E.E.Technician

in article snipped-for-privacy@storefull-3255.bay.webtv.net, Roy Q.T. at snipped-for-privacy@webtv.net wrote on 3/18/05 2:03 PM:
IT IS A CABIN NOT A TRAILER.
I've run my own cable because the electric company wanted me to cut a 20' easement of trees to put up poles and run the electric service.
I opted to have my meter base on a pole (similar to a mobile home setup) with a 200 AMP service box that is being used as the meter base and disconnect. It is grounded to a copper rod sunk 8' deep into the earth.
From that service box(on the pole) I've run two 4/0 HOT conductors and one 2/0 neutral underground. I have not run a separate grounding conductor.
On the cabin, there is another 200 AMP service box. At the moment only the to hots and the neutral are connected to it (The power is not one by the way)
My question was: Do I ground the service panel on the cabin and if so do I isolate the ground from the neutral.
I'm clear on the fact that I require a secondary ground, what I'm not clear on is wheather or not I isolate it from the ground.
Also, I'm guessing I will have to use a much larger conductor than a #6 for the ground. Do I use the same size throughout the grounding system?
Randy Tarin

| I've run my own cable because the electric company wanted me to cut a 20' | easement of trees to put up poles and run the electric service.
Those bastards! Always wanting to cut down trees.
| I opted to have my meter base on a pole (similar to a mobile home setup) | with a 200 AMP service box that is being used as the meter base and | disconnect. It is grounded to a copper rod sunk 8' deep into the earth. | | From that service box(on the pole) I've run two 4/0 HOT conductors and one | 2/0 neutral underground. I have not run a separate grounding conductor.
That lack of separate grounding conductor will make it more difficult.
| On the cabin, there is another 200 AMP service box. At the moment only the | to hots and the neutral are connected to it (The power is not one by the | way) | | My question was: Do I ground the service panel on the cabin and if so do I | isolate the ground from the neutral.
This would be similar to a building to building feed. In this case the pole is the main location, and the cabin is the subfeed location. If you had fed this with the extra ground wire, you would need to keep the neutral and ground separate. But since there is no ground wire, you need to drive a couple grounding electrodes, ground a new grounding wire to them, and bond the neutral to that.
But, there is one more issue. Any other metallic runs of anything, be it water pipe, cable TV, or telephone, must stay AWAY from that pole. Any current imbalance on the neutral will attempt do flow in parallel over anything grounded at both ends near each point the power is grounded.
| I'm clear on the fact that I require a secondary ground, what I'm not clear | on is wheather or not I isolate it from the ground.
You need to ground the neutral at both ends due to lack of grounding wire in order to protect against extreme voltages induced by weather.
But that said, I also know this is not that great a protection. By grounding the neutral on each end, it will ground out these voltage differences. But the hot wires are still poorly protected by that.
An alternative that I feel is safer, although more expensive, is to use a transformer to derive a neutral at the cabin, and just power it with the two hots only. Then the 3rd wire can be used as a true ground (but do not connect it to the neutral supplied by the power company in this case). This could be an auto-transformer, which would provide a DC path to ground for any static charge buildup.
| Also, I'm guessing I will have to use a much larger conductor than a #6 for | the ground. Do I use the same size throughout the grounding system?
It's best to have the grounding wire be the same size as current conductors anywhere they are. The code allows smaller grounding wire in certain cases, but you should be fine with the same size everywhere.

Roy Check the code definition of a feeder. What we have here is a three wire circuit between a yard pole mounted service and a separate structure many feet away. The conductors between the service equipment are an "outside feeder." They are therefore governed by ARTICLE 225 Outside Branch Circuits and Feeders of the US NEC. Outside feeders can be run in two different configurations. One is with an isolated Grounded Current Carrying Conductor (neutral) and a separate Equipment Grounding Conductor (EGC). The other is with a bonded neutral and no separate EGC. The second method is what the OP has already in place. There is simply no requirement in the code for feeder conductors run outside of buildings to contain an EGC in the absence of parallel conductive paths between the two points.
The more important point is what difference it would make electrically. In the absence of an Over Current Protective Device (OCPD) at the yard pole no one would be the least bit concerned about the absence of an EGC in the feeder to the building. How does the presence of a Service Disconnect and OCPD change the situation. If the OP would go down to home depot and buy a two hundred dollar plastic shed and assemble it over the Yard pole equipment no one would have any doubt that the three wire feeder was permitted because that shed would be a building and we would have a service in one building supplying another without parallel metallic pathways between them. What someone will have to do is explain how the absence of a shed or generator or guard shack at the yard pole makes any difference in the instant case. Indeed the absence of a building at the yard pole makes it far less likely that a metallic pathway will be installed later thus making the three wire feeder problematic.
If I were in the OPs position and someone tried to make me change the feeder I would pull the fused switch or breaker of of the yard pole and convert the feeder to an underground set of service entry conductors thus ending the quarrel right there. -- Tom H

in article 6rJ_d.14466$ snipped-for-privacy@newsread2.news.atl.earthlink.net, HorneTD at snipped-for-privacy@mindspring.com wrote on 3/18/05 5:24 PM:
Tom,
I'm the OP.
From your explaination, it sounds like I'm good to go.
I found this explaination online:
The following are key points for this installation:
1. The subpanel is located in or on a building or structure supplied from a separate building or structure.
2. The subpanel is supplied by a three-wire feeder (two ungrounded [hot] conductors and one grounded [neutral] conductor). An equipment grounding conductor is not run with the feeder.
3. There are no continuous metallic paths bonded to the grounding system in both buildings or structures involved (no parallel neutral paths, i.e., water pipes, gas pipes, metal raceways, and so forth).
4. Ground-fault protection of equipment has not been installed on the common AC service.
5. The neutral bus is bonded to the subpanel equipment grounding bus and enclosure (like the service equipment) and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded.
6. A grounding electrode system is required (just as it is for the service equipment), and the grounding electrode is connected to the neutral bus by a grounding electrode conductor sized according to Table 250.66 and based on the largest ungrounded (hot) conductor of the feeder. (Again, note the change from the 1999 NEC, where Table 250-122 was referenced.)
7. Water and gas pipes are required to be bonded to the neutral bus. See Sections 250.104(A)(3) and (B) for the bonding conductor size.

Correct. If the power company give you three wires you must use all three wires. If they give you four, you must use four.
Sorry, but you're screwed. You must absolutely have 4 wires. If the neutral gound link were not present in the meter base, that would make the meter base the code violation instead of your 3 wire circuit.. Both the grounded and grounding conductor must have separate continuity paths back to the initial ground
Unless someone can point me to a code exception for trailers.