Ok, I have the #2 4 wire stranded copper ran from house underground to barn. 2 hot leads to breaker at sub, whats next? Can anyone give me some details or laymans term diagrams. I know the electricians balk at me doing this myself but, I have a few days off and I like doing it. Yes it will get inspected. Ground rod is in place. How do I hook up grounds and neutral to meet code.
Thank you, I appreciate it! LMC
Replies
Not only will my post give you a reply to up yoour questions' chance of being read by someone who knows, but it will give me a chance to test my knowledge. You see, all I know I learned here at the UTBT.
Connect the Return Neutral Conductor wire (white) to the neutral buss, (the one that is insulated from the box case,) bond the neutral buss to ground.
Then connect the Equipment Grounding Conductor wire (green) to the equipment ground buss (the one that is mounted to the box without insulating standoffs) and also connect the equipment grounding buss to the ground rod.
Wait until my test gets graded before you do this (|:>)
SamT
There are three kinds of people: Predaters, Prey, and Paladins. For the life of me, I can't see why Prey feels safer from predators by disarming and emasculating Paladins.
You were close Sam,The neutral bus should not be bonded to the ground bus in a sub-panel. The neutral and ground should only be bonded in one place (generally back at the main panel).Jerry
You guys are good, Still more info Though!!!
Thanks again, LMC
I was thinking because this was a different building 100' away from the main Main.
Does that make a difference?SamT
There are three kinds of people: Predaters, Prey, and Paladins. For the life of me, I can't see why Prey feels safer from predators by disarming and emasculating Paladins.
Nope, no difference.Here's a good link on the subject and should answer all of Lou's questions.http://www.selfhelpandmore.com/homewiringusa/2002/accessory/detgarage/index.htmJerry
Jerry's right and I might add that the neutral buss must be isolated from the panel. usually it has a plastic or rubber piece under it.
Orbs
If there is no other metal paths between buildings then you can run 3 wires and bond the neutral, just like a serice entrance.But if you have run 4 wires, which he did, then you need to have isolated neutral and ground buses.But what was not mentioned was that how you provide a ground and neutral bus. Some panels have a single bus and you remove the bonding screw/strap. Then you need to insall a separate ground bus kits.Some others have one of each and come with a jumper or strap between them. In that case all you have to do is remove the jumper.In any case ground electrodes need to installed..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
If there is no other metal paths between buildings then you can run 3 wires and bond the neutral, just like a serice entrance.
But if you have run 4 wires, which he did, then you need to have isolated neutral and ground buses.
I knew there was something I didn't know.SamT
There are three kinds of people: Predaters, Prey, and Paladins. For the life of me, I can't see why Prey feels safer from predators by disarming and emasculating Paladins.
In any case ground electrodes need to installed
Noticed the plural use of electrodes.
You make a good point. There should be two grounding electrodes (ground rods). The first as close to the panel as possible and the second within 6' of the first. Both connected to the ground bus of the panel by an unbroken piece of #4 Cu. wire. In some places #6 is allowed.
Dave
"the second within 6' of the first."
You left out a key word: the second electrode should NOT be within 6' of the first. (NEC 250.56) (In fact, they function better when they are farther apart, as the FPN states).
"In any case ground electrodes need to installedNoticed the plural use of electrodes."Actually I was going to use ground electrode(s). But decided that was a whole other issue.Which I will briefly hit here. Depending on the type of electrodes used you can get by with one.If you have a Ufer ground (and being a new building he might) then you MUST use it as part of a ground electrode system.If you have an underground metallic water pipe in the building that underground portion is at least 10 ft long then it MUST be used as part of the ground electrode systems. However, a water pipe is not allowed to be the only ground electrode. So if you have that you need a secondary electrode(s).There is something in the code about metal framed buildings ('Bulter Buildings') but I dont't know the details. So if that is what he has more research is needed.There are several other types of ground electrodes, but most common is ground rod(s).The code requires that IF ground rod is used as a ground electrode then it must be tested for 25 ohms or less resistance or less 2 ground rods used (with at least a 6ft? spaceing). But the equipment for doing that is not common so in most cases 2 are being used in most cases.But if he has a ufer ground, that by itself is all that he needs..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Are you sure it is <i>within</i> 6 feet? I always understood that they had to be at <i>minimum</i> six feet apart - otherwise, you basically have one electrode.
In fact Taunton's "Wiring a House" (Rex Caldwell?) recommends that they be no closer than the lenght of the rods. This allows better disipation of the electricity into the earth.
When I hooked up my service installed 3 10' ground rods & they were each at least 12' apart - the inspector had no problems with it.
Bill, heres what i have
1- #2 stranded copper 4 pair
2- ran in conduit to house. when in crawl space I will have to go to ser cable, there is no way to bring conduit right to panel in house(jambed up rim joist, fireplace, etc.)
3- Installed ground rod at the detached structure
4- sub panel has two bus bars with a jumper (I remove-right?)
5- when i hook up my circuits neutrals go to neutral bus and grounds to grounded bus?(correct?)
6-Do i bond the ground bus?
7- what happens at the service side?
By the way, what made you go into the field. I see your into arts and entertainment as an accupation.
Thanks for the help, Lou
Edited 4/10/2007 6:07 am ET by loucarabasi
Edited 4/10/2007 6:08 am ET by loucarabasi
"By the way, what made you go into the field. I see your into arts and entertainment as an accupation."Well if you really believe what is in the profile you would not be listing to me. And right click on the picture and select View Image. My background is electrical ENGINEERING, although it was all in electronics and controls. My electrical experience as been as DIY, reading the code and other books and now doing a little handyman work being semi-retired."4- sub panel has two bus bars with a jumper (I remove-right?)5- when i hook up my circuits neutrals go to neutral bus and grounds to grounded bus?(correct?)6-Do i bond the ground bus?"It depends on the exact details of your panel.If you have one bus that is directly screwd to the panel then it is bonded and ground bus. The other bus should be attached to an insulating mount.I think that some might have two isolated buses with a two piece stape that bonds in the middle. If you have that type of system then you leave the one strap from the bus to the case."7- what happens at the service side?"First, if you have not already done it ID the wires. Often these wires are all black. Get some green and white tape to ID the ground and neutral wires. You can also mark one of the hots red, but unless you have a surplus of red tape it isn't worth it. You can swap them.The two hots land on the feeder breaker.The neutral lands on the neutral bus and the ground lands on the ground bus. You might need to get lugs for your bus if you are out of big holes.If this panel is also the service disconnect (which is most common) then the ground bus and neutral bus are the same. .
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
If there is no other metal paths between buildings then you can run 3 wires and bond the neutral, just like a serice entrance.
Please cite a code section for this statement - I can't find anything in NEC that would allow that, and I have never seen it done.
Not to highjack the thread, but a realted question . . . .I am also installing a 100A subpanel in an ATTACHED garage. The ground and neutral busses will be isolated from one another with the ground bonded to the panel enclosure and the neutral isolated from the panel enclosure. My understanding is since the garage is attached, I DO NOT need a separate set of grounding electrodes. It is also my understanding that separate grounding electrodes are only required if the subpanel is in a detached building. Is my understaning correct? I would hate to run 4 wires and get it all connected only to find that I need to run some #6 and pound in some electrodes. (which coincidentally would only be 4 feet from the existing service entrance.)And does anyone know what size AL conductors I would need to run for 100A service. I know I would need #4 Cu but will most likely run AL. I think table 310 shows #6 but can't remember.
"I DO NOT need a separate set of grounding electrodes. It is also my understanding that separate grounding electrodes are only required if the subpanel is in a detached building. Is my understaning correct?"That is correct.Just to clarify for eveyone as this is often a confusing area.I am simplifiying it some what, butBasically the equipment grounding conductor (aka, The Ground wire) is used to protect against fault currents if the hot shorts to a metal case or to other metal in the house (most commonly water pipes).The ground electrode system (Ground Rods, underground metalic water pipes, etc) is used to protect against lightning strikes or induced surges in the external feeder wires."And does anyone know what size AL conductors I would need to run for 100A service. I know I would need #4 Cu but will most likely run AL. I think table 310 shows #6 but can't remember."You are way off in the sizes.First table 310-15(b)(6) can't be used. That is limited to feeders that supply residential loads. What you have is sub-set of those loads and thus does not have the diversity.For 100 amps if you are runing a 75C wire (or better) (individual THNN wire or SE cable) and if connections at each end is rated 75 then you can use #3 CU or #1 AL.Otherwise (and this includes NM cable) you need to use the 50C column and is #2 CU or 1/0 AL.IF this is just a shop 100 amps is a lot, typcially 60 is more than enough. But if this also feeds some house loads (stove, hot tub, AC) then you might need it..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 4/10/2007 10:08 am by BillHartmann
The sub will feed the garage and a new laundry with electric dryer. And who knows what the future holds? Maybe a hot tub or mig welder. I know 100A is a lot, but figured it's easier to put it in now than upgrade later. I also plan to relocate several circuits to this box (like my well pump and refrigerator) and use it with a transfer switch for generator backup. That way I can keep water flowing and fridge and freezer running. I really don't need the capacity as much as the space. A big 100A box should provide all the capacity and space I may need in the future. Current 200A main panel is full. Thanks for the clarification on the wire size. I will double check the charts to see where I went astray.
I see that you migtht need the the larger feed.But, just as an aside, I often recommend 100 amp panels for workshops, but to feed them with 60 amp circuits.100 amp panels are common (ie; cheap) and in general have many for slots than 60-80 panels..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"250.32 Buildings or Structures Supplied by Feeder(s) or Branch Circuit(s)
(A) Grounding Electrode Building(s) or structure(s) supplied by feeder(s) or branch
circuit(s) shall have a grounding electrode or grounding electrode system installed in
accordance with 250.50. The grounding electrode conductor(s) shall be connected in
accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the
grounding electrode(s) required in 250.50 shall be installed."..."(2) Grounded Conductor Where (1) an equipment grounding conductor is not run with
the supply to the building or structure, (2) there are no continuous metallic paths bonded
to the grounding system in each building or structure involved, and (3) ground-fault
protection of equipment has not been installed on the supply side of the feeder(s), the
grounded conductor run with the supply to the building or structure shall be connected to
the building or structure disconnecting means 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. The size of the grounded conductor shall not be smaller than the
larger of either of the following:
(1) That required by 220.61
(2) That required by 250.122"And from the 2005 NEC Handbook."Similar to the provisions of 250.30(A)(3), the requirement in 250.32(B)(2) eliminates
the creation of parallel paths for normal neutral current on grounding conductors, metal
raceways, metal piping, and other metal structures. In the 1999 and previous editions
of the Code, the grounding electrode conductor and equipment grounding conductors
were permitted to be connected to the grounded conductor at a separate building or
structure. This multiple-location grounding arrangement could provide parallel paths
for neutral current along the electrical system and along other continuous metallic
piping and mechanical systems as well. Connection of the grounded conductor to a
grounding electrode system at a separate building or structure is permitted only if these
parallel paths are not created and if there is no common ground-fault protection of
equipment provided at the service where the feeder or branch circuit originates.
Where the grounded conductor is used as part of the ground-fault current return circuit,
it is required to be sized no less than that required by 250.122 for equipment grounding
conductors, but it also has to be sized to carry the maximum unbalanced load, as
specified in 220.61.
Like the grounded service conductor, a branch-circuit or feeder grounded conductor
used in the application permitted by 250.32(B)(2) is a circuit conductor for normal
neutral current and is also the circuit conductor used to create an effective ground-fault
current return path. Therefore, it is necessary to size the grounded conductor in this
application based on which of those two functions requires the larger conductor. Of
course there is no prohibition on installing a full-size grounded (neutral) conductor,
thus ensuring compliance with both 250.122 and 220.61.".
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
> If there is no other metal paths between buildings then you can run
> 3 wires and bond the neutral, just like a serice entrance.No, you can't. The way the inspector explained it to me, the safety ground wire on your cable is smaller than the neutral conductor. If you bond the neutral and ground busses in the subpanel and the neutral conductor (or its connections) goes bad, all of the sub-panel circuits will continue to work, using the safety ground wire as the neutral conductor. This is considered an unsafe condition.You have to have independent neutral and ground lines all the way back to the main panel. With the Square-D sub panel I used in my shop, this is done by adding a ground buss, removing the green screw that connects the neutral buss to the case, and using a supply cable with three conductors and a ground.George Patterson, Patterson Handyman Service
"> If there is no other metal paths between buildings then you can run
> 3 wires and bond the neutral, just like a serice entrance.No, you can't. The way the inspector explained it to me, the safety ground wire on your cable is smaller than the neutral conductor. If you bond the neutral and ground busses in the subpanel and the neutral conductor (or its connections) goes bad, all of the sub-panel circuits will continue to work, using the safety ground wire as the neutral conductor. This is considered an unsafe condition."If you only run 3 wires then you don't have an equipement grounding conductor between the main panel and the detached building.This is the same as service entrance and is just as safe or unsafe as a service entrance with a 3 wire drop from the POCO. Actually it is a little safer, as in general, the connects are not in the weather like a POCO drop.Here is the code.http://forums.taunton.com/tp-breaktime/messages?msg=88378.18.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
> If you only run 3 wires then you don't have an equipement grounding
> conductor between the main panel and the detached building.Well, according to the local inspector and the electrician who ran the service to the house across the street, that won't pass in New Jersey. You need 4 wires, one of which is a ground. That's true even if the distance between the subpanel and the main panel is only a few inches.George Patterson, Patterson Handyman Service
"You need 4 wires, one of which is a ground. That's true even if the distance between the subpanel and the main panel is only a few inches."Now that is important. It is not a detached building. One of the bases of the codes is that any metal in a building should be at the same potential. And to guarantee it you need a EGC that does not normally carry current.But a detached building is different. And the NEC does allow 3 wire feeder, if there is no other metallic paths.But the thing to realize that there is no such thing as a National Electrical Code, other than in name only. Nor is theere an Internation Building Code. The only code that affects any area is whatever is adopted by that communities legistation. Typically references a specific model code, plus local amendments. So you need to know what those are to find out what the "real code" is in your area.For example I have seen several local amendments that don't require AFCI's. And I have heard that Washington state amendments don't allow for the 3 wire feeders to detached buildings..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
> And the NEC does allow 3 wire feeder, if there is no other metallic
> paths.As I recall, earlier in this thread there were several recommendations to bury the cable in metallic conduit.George Patterson, Patterson Handyman Service
Well, according to the local inspector and the electrician who ran the service to the house across the street, that won't pass in New Jersey.
That's true in a lot of places. I can see how BH wants to "read that into" the code, and I think you could make a reasonable argument to support his view, but that is not how the code is commonly interpreted, in my experience, and it would not pass inspection in a lot of places.
This is the adoptions and amendments to the codes for NJ.The electrical starts on page 21.http://www.state.nj.us/dca/codes/code_assist_internet/barrier_free/pdf/model_codes_tech_amend_2_20_07.pdfThere are no amendments for ground, bonding, feeders, overload protection or anything else that is being discussed here..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
When the inspector says it won't pass, it really doesn't matter what the book says.George Patterson, Patterson Handyman Service
I think you are both right.Bill is saying that you can bond nuetral and ground on a detached building with 3 wire service. You are saying you cannot bond nuetral and ground on a detached building with 4 wire service.Too many grounds and nuetrals and electrodes and busses.A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.
What Bill says in regard to a separate building makes complete sense electrically and he can back it up with code. It may be one of those "it's just the way it's always been done around here" things.Not an electrician, just pretending to be one,
Jerry
Bill is right ! That is a very common practice where we build. If the building is detached and there are no other (any kind) of metal conductors between the buildings, then you can treat the outbuilding as a normal service entrance.
We have had four different inspectors in the last 15 years and they all use that method without question. In fact the last one told a friend of mine specifically that he didn't need to run the grounding wire between the buildings and explained why.
Bill, my heads a spinnin!!! Why don't you just come over and do it!!! I'll Fly you in
Thanks Lou