Grounding Rods - Attached vs. Detatched structure

[pattenp]

Well.. I'm down for the count on this one. Time to move on.

 

[PRH44]

Just ran through this thread. Lots of information being tossed around. Very good points are being made.
There are different avenues to take when determining how to ground or bond a given portion of an electrical system.
I will address the OPs concerns or shall I say my interpretation of his concerns
1) It appears That most of you agree That an additional ground rod at the sub panel is not mandatory. I would agree it is not required in the same structure.
2) Speedy, Aceman, pattenp have all stated this additional ground rod would be allowed by the NEC. I would Agree, You guys please let me know if I am misstating your intent or interpretation. However you need to qualify the intent of the ground rod to determine how it is to be connected to the system. In this question it is assumed you will be installing an "Auxiliary Grounding Electrode" rod allowed by 250.54. This rod must be attached to the EGC (equipment grounding conductor) at the sub panel as the earth cannot be the sole ground return path. Auxiliary ground rods do not fall under the bonding requirements of 250.50 as a supplemental electrode would.
The arrangement in this sub panel would need to be as follows.
The Neutral (also know as the grounded conductor) would be required to be terminated on an insulated neutral bar. No bond screw installed or ground wire and or EGC to be terminated on this bus.
The grounding conductor (EGC-equipment grounding conductor) AKA "ground wire" is to be terminated to the sub panel chassis or approved ground bus.
Should an "auxiliary" ground rod be driven it will be connected to the EGC bus.

3)Now this question, you have experienced damage already. You are doing the right thing by "Bonding" your water pipe to your grounding electrode system.
I prefer and recommend bonding all metal systems in your home to the electrode system as the NEC states. Underground gas pipe is exempt as it is not allowed by the NEC.
Driving Auxiliary Electrode ground rods can create some difference in potential so it is imperative you attach this to the EGC. This will keep all grounding at the same potential. I personally prefer not to do this as I prefer to create a very well bonded grounding electrode system grid through out my home. Then using EGCs size correctly and terminated very soundly keeping it all a one way path to ground. Just my personal preference.
Additional grounds rods such as supplemental need to be bonded together and fall under 250.50 requiring them to be bonded to the grounding electrode system/conductor. The purpose is to lower the over all resistance for your system
Clear as mud??

 

[pattenp]

Right on PRH44. Oh... shoot, I said I was moving on.

 

[Falcon67]

Not intending to kick this too much further down the road but
>Technically because the garage is attached to the house via a carport it’s >considered one structure

Who makes that determination - because local to me, this is not true. I was going to do this to get around boundary issues and the city does not recognize this "trick" as making the two one structure. Other places do, which is why I wanted to do it.

I also think to clarify things that 4 wires to a structure with a ground rod/UFER/whatever that also has no other metallic connection to the main structure will not be in danger of a ground loop because you'd have (per NEC) to have 4 wires, with that ground system tied to the grounded wire from the main panel. Which (ground loop) is what I think Speedy was avoiding saying out loud. I also read where Speedy says "3 or 4 wire" which is not in 2008 up NEC as I read it and has been discussed many times here - only 4 allowed now. Maybe on a farm, coming from the service drop?
Sic: "On unattached structure yes u can run three wires or four but u still have to grd. rods either way."

 

[Docholiday]

Not intending to kick this too much further down the road but
>Technically because the garage is attached to the house via a carport it’s >considered one structure

Who makes that determination - because local to me, this is not true. I was going to do this to get around boundary issues and the city does not recognize this "trick" as making the two one structure. Other places do, which is why I wanted to do it.

I also think to clarify things that 4 wires to a structure with a ground rod/UFER/whatever that also has no other metallic connection to the main structure will not be in danger of a ground loop because you'd have (per NEC) to have 4 wires, with that ground system tied to the grounded wire from the main panel. Which (ground loop) is what I think Speedy was avoiding saying out loud. I also read where Speedy says "3 or 4 wire" which is not in 2008 up NEC as I read it and has been discussed many times here - only 4 allowed now. Maybe on a farm, coming from the service drop?
Sic: "On unattached structure yes u can run three wires or four but u still have to grd. rods either way."

it depends on the jurisdiction how they want to enforce this. Clackmas County for example says either or..Three wire has its advantage on a remote structure.

 

[Speedy Petey]

Not intending to kick this too much further down the road but
>Technically because the garage is attached to the house via a carport it’s >considered one structure

Who makes that determination - because local to me, this is not true. I was going to do this to get around boundary issues and the city does not recognize this "trick" as making the two one structure. Other places do, which is why I wanted to do it.

I also think to clarify things that 4 wires to a structure with a ground rod/UFER/whatever that also has no other metallic connection to the main structure will not be in danger of a ground loop because you'd have (per NEC) to have 4 wires, with that ground system tied to the grounded wire from the main panel. Which (ground loop) is what I think Speedy was avoiding saying out loud. I also read where Speedy says "3 or 4 wire" which is not in 2008 up NEC as I read it and has been discussed many times here - only 4 allowed now. Maybe on a farm, coming from the service drop?
Sic: "On unattached structure yes u can run three wires or four but u still have to grd. rods either way."

Ground loops have nothing to do with AC wiring. That is an electronics thing where loops can cause interference, etc.
Some folks like to apply the term, but in real world construction electric the term is simply not used.

 

[Speedy Petey]

I also read where Speedy says "3 or 4 wire" which is not in 2008 up NEC as I read it and has been discussed many times here - only 4 allowed now. Maybe on a farm, coming from the service drop?
Sic: "On unattached structure yes u can run three wires or four but u still have to grd. rods either way."

Not in this thread, or any other. If I wrote that elsewhere it was with regard to existing installations only.
The "3-wire exception" was removed quite a while ago. I can't think of an area that would still allow it.
What is that quote in bold from?

 

[Speedy Petey]

I also read where Speedy says "3 or 4 wire" which is not in 2008 up NEC as I read it and has been discussed many times here - only 4 allowed now.

Are you referring to this:

I'm sorry, but this is COMPLETELY wrong.

A ground rod does NOT derive a ground such as an equipment ground. A grounding electrode has NOTHING to do with the equipment ground in so far as clearing faults or tripping breakers.

A grounding electrode was always required at a detached structure served by a feeder, regardless if it was an older (allowable under certain circumstances) 3-wire feeder or the typical 4-wire feeder. Again, this feeder had NO relationship to the grounding electrode.

 

[PRH44]

Not intending to kick this too much further down the road but
>Technically because the garage is attached to the house via a carport it’s >considered one structure

Who makes that determination -

That would be the local Authority, if not the same structure a different set of rules will apply. The OP should check this.

 

[Aceman]

Your definitely not in the trade. Your wrong I have said what issue is and yes, your wrong. The reason you don't understand is bc you don't have any background about electrical.

I'm not in the trade, huh?

I guess I lied when I put my occupation in my profile?

The bottom line is, you've been on this site for all of 5 mins and you don't know anyone on here or what their background is.

 

[pattenp]

Damn.. you're an electrician! And all this time I thought you were a beautician.

I'm not in the trade, huh?

I guess I lied when I put my occupation in my profile?

The bottom line is, you've been on this site for all of 5 mins and you don't know anyone on here or what their background is.

 

[Slapshot67]

This was very helpful. Thx to whomever posted.

http://www.selfhelpandmore.com/home...o-dwellings/wiring-a-detached-garage-2002.php

Pictorial Example of a Garage Panel with 3 Or More Circuits 240 Volt 60 Amp, 100 Amp, 200 Amp Branch Circuit with Underground Conductors with an Equipment Grounding Conductor Ran with the Feeder Supplying the Detached Structure

http://www.selfhelpandmore.com/images/home-wiring-usa/accessory/detached-garage/detgar8.jpg

Special Note:*@#$Any detached structure that has an existing non-current carrying metallic path such as water pipes installed between the main structure and the detached structure must have an equipment grounding conductor installed with the feeders installed between the two buildings. Article 250-32-B-1 & 2

Note # 1*@#$–A grounding electrode conductor is the sole connection between the grounding electrode {usually a ground rod}, and the main panel of that structure that grounding electrode serves. The minimum size grounding electrode conductor recognized as a grounding electrode conductor is a # 8 copper for 100 amps or less. Article 250-66 The maximum size grounding electrode conductor required for a made electrode is a # 6 copper for any size service. Article 250-66-A No aluminum conductor may be used for grounding in direct contact with the earth. Article 250-64-A The minimum grounding electrode {made electrode such as a commercially made ground rod} allowed is a ½”factory made grounding electrode that is ½”in diameter X 8’in length Article 250-52.

Note # 2*@#$–A branch circuit is the circuits installed within a structure to serve your luminaries, {light fixtures}, and your switches, and your receptacles.

The garage main panel, if 100 amps is allowed 24 branch circuits to be installed in that panel. If 200 amps is allowed 42 branch circuits in that panel. Article 384-15 This main panel may have a maximum of 6 single pole or 6 double pole breakers installed as a maximum in that panel, without having a main disconnect installed in that panel. The 6 breakers whether single or double pole may act as six main disconnects as allowed serving a structure. Article 225-33 The main disconnect (s) serving this detached garage may be installed either outside and weatherproof Article 225-32 and 373-2 or nearest point of entrance inside and not weatherproof. Article 225-32 and 225-39 and 225-31These main disconnects must be grouped. Article 225-34

Note # 3*@#$–When the detached garage service panel is supplied by a feeder that has an equipment grounding conductor ran from the main structure {usually dwelling} to the detached garage, then the neutral bar, and equipment grounding bar must be kept separated. Article 250-32-B-1 The equipment grounding bar must have a main bonding jumper connecting that equipment grounding bar to the metal of the panel box. Article 250-102-E The neutral bar must be kept isolated from the metal of the panel box and the neutral must be kept separated from the equipment grounding bar. Article 250-32-B-1

Note # 4*@#$- If there is no grounding electrode system serving the detached garage, then you must install a new grounding electrode system as described in Article 250-50. If none of those listed in Article 250-50 is available, then you may use a made electrode as found in Article 250-52. Article 250-50 lists any metal water pipe in direct contact with earth, any rebar in concrete, any grounding rings, and many more as an approved grounding electrode used connected together to make the grounding electrode system. If available, all of those grounding electrodes listed in Article 250-50 must be connected together to make the grounding electrode system.

Remember that if a non current carrying metal path exists between the two buildings connecting the two buildings, then you must install an equipment grounding conductor with the feeder installed, serving that second building from that main building. If this non current carrying metal path exists, then refer to the section explaining how to wire a detached structure with 30 amps maximum and with an equipment grounding conductor ran with the feeders between buildings. If you have a metal water pipe ran underground, but that metal water pipe does not make contact between the two buildings, and if your metal water pipe, located at that detached structure, is in direct contact with earth, then that metal water pipe, and any other grounding method listed in Article 250-50 must be connected together to make that grounding electrode system. If that metal water pipe is installed in direct contact with the earth, but not installed connecting the two buildings, then you must use that metal water pipe in direct contact with earth as part of the grounding electrode system, but you must also supply a supplemental grounding electrode to back up that water pipe in case that metal water pipe is removed at a later date. Article 250-50-A-2Remember, If any metal connection is existing between that main building and that detached garage then you must install that equipment grounding conductor between the two buildings with that feeder and as a part of that feeder installed between the two buildings. Article 250-32-B-1 & 2

Note # 5*@#$–Minimum burial depth in a residential setting must be at least 18”deep unless in rigid or IMC threaded conduit these two conduits must be a minimum of 6”deep, if buried. Table 300-5.

Note # 6*@#$- No part of this feeder from the breaker in the dwelling to the disconnect form in that detached garage may be rated in ampacity that is smaller than the overcurrent device {breaker or fuse} protecting that feeder in the dwelling’s panel. Article 210-19 & 215-2 & 220-3 & 220-10 & 240-3 & 240-6 If you install a 60 amp breaker 240 volt in the dwelling, then you may use a 6/3wGrnd UF copper cable from that dwelling’s panel to that garage disconnect. If you install a 100 amp breaker 240 volt in the dwelling, then you may use a 2 awg four wire URD aluminum cable from that dwelling’s panel to that garage disconnect. Article 338-3 If you install a 200 amp breaker 240 volt in the dwelling, then you may use a 2/0 awg four wire URD aluminum cable from that dwelling’s panel to that garage disconnect. Article 338-3 Approved wiring for underground can be but not limited to Type UF cable or URD cable if direct buried Article 338-3, or Type THWN, or THW, or TW if protected by a conduit. Article 310-13 You may install PVC schedule 40 when underground Article 347-2-G, or schedule 80 when exposed to physical damage Article 347-3-C, or rigid Article 346-3, or IMC conduits Article 345-3. Seal tight may be used for burial if listed for underground use Article 351-4-A-3. Type 2 non metallic seal tight may be used if listed for underground use as direct burial and sunlight resistant. Article 351-23-3 & . 251-22-2Type 2 non metallic seal tight is a seal tight that is as described {A smooth inner surface with integral reinforcement within the conduit wall, designated as Type LFNC-B}. ENT {electrical nonmetallic tubing} is not allowed to be used in direct sunlight or if buried Article 331-4. ENT {electrical nonmetallic tubing} is not allowed to be used in direct sunlight or if buried Article 331-4. If you install the above conductors with a conduit protection then you must install two black wires, one white or gray wire and one green of bare wire. If the conduit is metal the metal the metal conduit may be used instead of the green or bare wire as the equipment grounding conductor. The minimum size conductors are as follows; 60 amp copper = 6 awg or 4 awg aluminum Table 310-16& 240-3-B. 100 amp copper = 4 awg or 2 awg aluminum Table 310-15-B-6. 100 amp copper = 2/0 awg or 4/0 awg aluminum Table 310-15-B-6.

Now there is heavy controversy whether you may use table 310-15-b-6 while installing feeders to a detached residential garage. You should confirm with your local electrical inspector to confirm if you must use table 310-16 or table 310-15-b-6 when installing a feeder between the main dwelling and the detached garage. Table 310-16 calls for the following sizes; 60 amp copper = 6 awg or 4 awg aluminum Table 310-16 & 240-3-B. 100 amp copper = 3 awg or 1 awg aluminum Table 310-16. 200 amp copper = 3/0 awg or 4/0 awg aluminum Table 310-16 & 240-3-B.

Do not use EMT (electrical metallic tubing) in direct contact with earth. Article 331-4-A-5.

Note # 7*@#$–Load side of disconnect serving the branch circuit wiring in the detached garage itself. This service panel installed inside your detached garage is where you start wiring the branch circuits serving the inside of your garage from, normally using nonmetallic sheathed cable. However there are many wiring styles allowed to wire the inside of this detached garage.

 

[Stuart in MN]

This was very helpful. Thx to whomever posted.

http://www.selfhelpandmore.com/home...o-dwellings/wiring-a-detached-garage-2002.php

Don't know if it was me you were referring to, but I've posted that link a few times. One important thing to note is the article is old, and was based on the 2002 edition of the National Electric Code (most parts of the US are up to the 2011 or 2014 NEC today.) As a result, there may have been some things changed since that article was written, but in general it's a good basic reference.

 

[wyliesdiesels]

Damn did i get a chuckle on this thread ESPECIALLY when DOC(who is no longer on this forum) kept yelling FIRE....

I also learned something and will probably learn some more as I finish reading it!

Oh and yeah, that part about Aceman(who is a master electrician) not being in the trade was especially funny!

 

[C96]

I realize this is an old thread and prior to my joining, so, I’m happy that it was resurrected!

A very good debate indeed and a very important one!

Although I believe pattenp had it right from the start, PRH44 pretty much summed it up.

Great job on this one guys

As far as Docholiday and why we haven’t heard from him, well, I’m thinking something like this must have happened to him:

 

[sberry]

Ground loops have nothing to do with AC wiring. That is an electronics thing where loops can cause interference, etc.
Some folks like to apply the term, but in real world construction electric the term is simply not used.

Well they kind of do.

 

[macdabs]

I won't even bring up R-56 Grounding at communications site. Everything is grounded and bonded together that is metal. From the boxes to the A/C grates , fence posts, doors to the frames all grounded.

Mac

 

[wyliesdiesels]

I won't even bring up R-56 Grounding at communications site. Everything is grounded and bonded together that is metal. From the boxes to the A/C grates , fence posts, doors to the frames all grounded.

Mac

Exactly! Im an electrician at a radio shop and we do R-56 grounding for customers EVERY WEEK!

Just started a grounding project last week at an AMR dispatch center! Tons of stuff to ground! Lots of wire used JUST for grounding!