I have recently installed 100A service to my detached garage from a 100A breaker in my main (house) service panel (underground 3-wire without grounding conductor). The sub-panel in the garage does NOT have it's own main disconnect. The sub- panel does have it's own ground bar. The article on the website says to bond the neutral bar with the grounding bar (in the garage sub-panel). Another wiring reference I have says it "must NOT be bonded ...... if the switch is used as a panelboard on the load side of a service".

Should I bond or not bond?

Thanks!

re: Detached Garage sub-panel	Warren Goodrich	1:21 pm sunday september 9, 2001

You seem to be looking at this panel in that detached structure as a sub panel. This panel in that detached structure can not be a sub panel the way that you wired it. You said you ran three conductors without an equipment grounding conductor. Any subpanel must have an equipment grounding conductor ran with the feeder. Therefore you have a main service rated panel requiring a main breaker. There is an exception to having one main disconnect and that is if you have a maximum circuit panel of 6 breakers. You may then use the six branch circuit breakers as 6 main disconnects serving that one building.

Now if you had run an equipment grounding conductor between the two buildings with the feeder to that second building and you had a breaker in that first building then the AHJ can rule that you have safe switching allowing no main breaker located at that second building but using the breaker in the first structure serving that second structure as the main disconnect for that second structure.

We may have and I do invite other opinions to be posted as replies to this subject. There is an on going difference of opinions on this subject. I would like a variety of thoughts as replies if we can get them.

The following reply by me will be copies of the NEC sections that apply to support my interpretation. Have fun getting confused as you read the rules of law.

Hope this helps

Wg

re: Detached Garage sub-panel	Warren Goodrich	1:25 pm sunday september 9, 2001

I also forgot to mention that with you running only three wires and not including an equipment grounding coductor with that feeder to that detached structure served by a common service from the main structure. You must install a new grounding electrode system [commonly a ground rod] at the second structure.

Sorry forgot to make the clear on the first reply.

Wg

re: Detached Garage sub-panel	Warren Goodrich	1:29 pm sunday september 9, 2001

The following are copies of Code sections that apply to your questions.

225-31. Disconnecting Means Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.

225-32. Location The disconnecting means shall be installed either inside or outside of the building or structure served or where the conductors pass through the building or structure. The disconnecting means shall be at a readily accessible location nearest the point of entrance of the conductors. For the purposes of this section, the requirements in Section 230-6 shall be permitted to be utilized.

Exception No. 1: For installations under single management, where documented safe switching procedures are established and maintained for disconnection, the disconnecting means shall be permitted to be located elsewhere on the premises.

225-33. Maximum Number of Disconnects

(a) General. The disconnecting means for each supply permitted by Section 225-30 shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be no more than six disconnects per supply grouped in any one location.

250-32. Two or More Buildings or Structures Supplied from a Common Service

(a) Grounding Electrode. Where two or more buildings or structures are supplied from a common ac service by a feeder(s) or branch circuit(s), the grounding electrode(s) required in Part C of this article at each building or structure shall be connected in the manner specified in (b) or (c). Where there are no existing grounding electrodes, the grounding electrode(s) required in Part C of this article shall be installed.

Exception: A grounding electrode at separate buildings or structures shall not be required where only one branch circuit supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the noncurrent-carrying parts of all equipment.

(b) Grounded Systems. For a grounded system at the separate building or structure, the connection to the grounding electrode and grounding or bonding of equipment, structures, or frames required to be grounded or bonded shall comply with either (1) or (2).

(1) Equipment Grounding Conductor. An equipment grounding conductor as described in Section 250-118 shall be run with the supply conductors and connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).

(2) Grounded Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, and (2) there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and (3) ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit 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.

(c) Ungrounded Systems. The grounding electrode(s) shall be connected to the building or structure disconnecting means. (d) Disconnecting Means Located in Separate Building or Structure on the Same Premises. Where one or more disconnecting means supply one or more additional buildings or structures under single management, and where these disconnecting means are located remote from those buildings or structures in accordance with the provisions of Section 225-32, Exception Nos. 1 and 2, all of the following conditions shall be met.

1. The connection of the grounded circuit conductor to the grounding electrode at a separate building or structure shall not be made.

2. An equipment grounding conductor for grounding any noncurrent- carrying equipment, interior metal piping systems, and building or structural metal frames is run with the circuit conductors to a separate building or structure and bonded to existing grounding electrode(s) required in Part C of this article, or, where there are no existing electrodes, the grounding electrode(s) required in Part C of this article shall be installed where a separate building or structure is supplied by more than one branch circuit.

3. Bonding the equipment grounding conductor to the grounding electrode at a separate building or structure shall be made in a junction box, panelboard, or similar enclosure located immediately inside or outside the separate building or structure.

(e) Agricultural Buildings or Structures. Where livestock is housed, any portion of the equipment grounding conductor run underground to the building or structure disconnecting means shall be insulated or covered copper.

FPN: See Section 547-8 for special grounding requirements for agricultural buildings.

(f) Grounding Conductor. The size of the grounding conductor to the grounding electrode(s) shall not be less than given in Table 250-122, and shall not be required to be larger than the largest ungrounded supply conductor. The installation shall comply with Part C of this article.

Have fun with your interpretation

Wg

re: Detached Garage sub-panel	Reuben	4:07 pm sunday september 9, 2001

Thanks for the response.

I have indeed installed a separate ground rod for the garage panel. Lets say my panel has only 6 circuits. Should I bond the neutral bar to the ground bar? I'm not as interested in interpreting the code as I am in having a safe electrical system.

Thanks again.

re: Detached Garage sub-panel	Warren Goodrich	5:57 pm sunday september 9, 2001

Yes you must marry any main panel in a detached garage that has a common service fed from the main structure as long as you did not run a fourth equipement grounding conductor with the feeder. If your ran a fourth wire then you would have to separate the neutral and grounding bars in that panel located in that detached structure.

You said you did not run an equipment grounding conductor with the feeder, therefore you must marry the neutral bar and the grounding bar as one entity in that detached garage panel.

I understand you don't want to worry about interpretation as to the NEC code requirements. However you must interpret it or have it interpreted for you. If you do not meet the Code requirements of the NEC then you did not meet the minimum safety standards set forth by the largest part of the world. The NEC is considered in most parts as a rule of law setting the minimum safety standards. If you do not meet those NEC rules and something happens such as structural damage or bodily injury, you will be held financially liable. As I understand your discription of your wiring method then you have met the NEC as long as you have no more than 6 circuits available in that garage panel and if you married the neutral and grounding bar as one entity.

Good Luck

Wg

re: Detached Garage sub-panel	Reuben	6:53 pm sunday september 9, 2001

Thank you.

If sometime in the future I would need more than 6 circuits would I meet code by using a panel that had it's own main disconnect?

Thanks.

re: Detached Garage sub-panel	Reuben	8:06 pm sunday september 9, 2001

If I use OSHA Lockout-Tagout procedures I interpret my garage as being Exception No. 1 of 225-23. What do think?

Thanks.

re: Detached Garage sub-panel	wirenuts	8:57 pm sunday september 9, 2001

It's nice that you are aware of LOTO, but i do not have a 225-23 in my 99' nec, is this a typo???

re: Detached Garage sub-panel	Reuben	9:00 pm sunday september 9, 2001

Sorry......225-32. Location....

Thanks for the response.

re: Detached Garage sub-panel	wirenuts	9:01 pm sunday september 9, 2001

Rueben;

by code, with a 3-wire, the G & N are married and bonded to the panel, there is a GEC (grounding electrode conductor) from this to an entirely new grounding electode system , that would equal the home serving it. Note there can be no mutual mettalic paths bettween house and garage here, the fear being a parralleled nuetral.

re: Detached Garage sub-panel	Warren Goodrich	8:50 am monday september 10, 2001

Actually you should check out not only 225-32 but also 250-32-d.

I know this will cause some more confusion but special grounding considerations have to apply using a common service concerning that grounding of those two buildings.

Wirenuts, how do you read 250-32.

As for a lock out tag out, this term is only mentioned for disconnects of motor loads. I am not sure which way [whether lock out tag out would be required by your AHJ] considering accessory buildings located on the same premises.

Curious

Wg

re: Detached Garage sub-panel	Reuben	12:17 pm monday september 10, 2001

After several hours of ruminating my interpretations are:

225-32 Location Exception #1: I can use my garage panel as a subpanel in a remote location on the same premises under single management.

250-32(d)1: I should not bond the neutral bar with the garage grounding electrode.

250-32(d)3: The garage panel needs to have it's own grounding electrode connected to the equipment ground bar.

Does this sound reasonable?

Thanks for everyone's help!

re: Detached Garage sub-panel	Warren Goodrich	6:11 pm monday september 10, 2001

You skipped the main road block in doing what you want to do.

REMEMBER THAT GROUNDED MEANS NEUTRAL CONDUCTOR AND GROUNDING MEANS EQUIPMENT GROUNDING CONDUCTOR.

250-32-D requires that three requirments must be met before you can use 225-32 speaking of that remote disconnect.

250-32-D-2 specifically says that you must run an equipment grounding conductor with the feeder from the main building.

250-32-D specifically says that you must meet all three requirements which would include requirment #2 demanding an equipment grounding conductor be ran with the feeder between the two buildings.

You only ran two hots and a neutral but no 4th conductor being the equipment grounding conductor.

Therefore you must marry the neutrals and grounding bars together as one entity and supply a main breaker serving as the main disconnect form and overcurrent device as dictated in 225-32 and 250-32-B-2

See below the copies of the codes dictating that you locate the main disconnect at that second building due to no equipment grounding conductor ran with the feeder from that main building.

Also see below the copies of the codes dictating that the neutral and grounding bar must be married.

225-32. Location

The disconnecting means shall be installed either inside or outside of the building or structure served or where the conductors pass through the building or structure. The disconnecting means shall be at a readily accessible location nearest the point of entrance of the conductors. For the purposes of this section, the requirements in Section 230-6 shall be permitted to be utilized.

250-32. Two or More Buildings or Structures Supplied from a Common Service

(d) Disconnecting Means Located in Separate Building or Structure on the Same Premises. Where one or more disconnecting means supply one or more additional buildings or structures under single management, and where these disconnecting means are located remote from those buildings or structures in accordance with the provisions of Section 225-32, Exception Nos. 1 and 2, all of the following conditions shall be met.

2. An equipment grounding conductor for grounding any noncurrent- carrying equipment, interior metal piping systems, and building or structural metal frames is run with the circuit conductors to a separate building or structure and bonded to existing grounding electrode(s) required in Part C of this article, or, where there are no existing electrodes, the grounding electrode(s) required in Part C of this article shall be installed where a separate building or structure is supplied by more than one branch circuit.

COMMENT;
The above requires that the main disconnect must be located at the second building because of the lack of the 4th equipment grounding conductor ran with the feeder from that main building. Exception 1 in 225-32 can not be used because all three conditions were not met in 250-32-D.

SEE A CONTINUATION OF THIS REPLY ON THE NEXT REPLY SHOWN, DUE TO THE LENGTH OF THIS REPLY AND THE LIMITS OF THIS FORUM, IT HAS BEEN SPLIT INTO TWO SECTIONS.

Wg

re: Detached Garage sub-panel	Warren Goodrich	6:16 pm monday september 10, 2001

250-32. Two or More Buildings or Structures Supplied from a Common Service

(b) Grounded Systems. For a grounded system at the separate building or structure, the connection to the grounding electrode and grounding or bonding of equipment, structures, or frames required to be grounded or bonded shall comply with either (1) or (2).

(2) Grounded Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, and (2) there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and (3) ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit 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.

COMMENT;
You ran as a feeder from the main building to the second building; two hots and a neutral with no equipment grounding conductor ran with that feeder. Therefore the above rule applies requiring that the neutral and grounding bar be joined as one entity in that second buildings panel as required in 250-32-B-2.

CLOSING COMMENT;
Now you still can get by without a main disconnect if your panel only has a maximum number of breaker openings of 6 circuits. If that panel is capable of accepting more than 6 circuits then you must install the main disconnect and main overcurrent device usually being one main breaker in that panel using a main service rated panel.

The following is a copy of that 6 main disconnect rule.

225-33. Maximum Number of Disconnects
(a) General. The disconnecting means for each supply permitted by Section 225-30 shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be no more than six disconnects per supply grouped in any one location. Exception: For the purpose of this section, disconnecting means used solely for the control circuit of the ground-fault protection system, installed as part of the listed equipment, shall not be considered a supply disconnecting means. (b) Single-Pole Units. Two or three single-pole switches or breakers, capable of individual operation, shall be permitted on multiwire circuits, one pole for each ungrounded conductor, as one multipole disconnect, provided they are equipped with handle ties or a master handle to disconnect all ungrounded conductors with no more than six operations of the hand.

May not be what you wanted to hear but thats the code sections involved in your design with no equipment grounding conductor ran with the feeder to that second building.

Hope this helps

Wg

re: Detached Garage sub-panel	Reuben	8:13 pm monday september 10, 2001

Thanks for all your help.

My panel has room for 8 circuits. I guess I need to purchase a 100A breaker for it to use as a main disconnect. I assume I hook the 2 hot wires directly to the breaker and leave the neutral where it is on the neutral bar. I need to bond the neutral bar to the equipment ground bar. Does this sound like it meets code?

As an alternative could I interupt the supply lines with an equipment disconnect switch and use it for the main disconnect freeing up all 8 circuits in my sub-panel?

Thanks.

re: Detached Garage sub-panel	Warren Goodrich	10:47 pm monday september 10, 2001

Depending on you panel will tell you how to join the neutral bar and grounding bar. If you have a grounding bar that is bolted directly to the case of the panel, and if this panel is also a main service rated panel, then you should have a bonding jumper with a green screw that is designed to attach to the neutral bar and then bolt to the case of the panel. This will join the two bars. Another method of bonding these two bars together again depending on the brand of panel is a long green screw that passes through the neutral bar and screws to the case of the panel.

Now to get a bit technical, when a main breaker is installed in a panel that main breaker is supposed to be securely mounted to the panel buss. Ususally a bracket clips that main breaker into place.

If you have a not service rated panel then you may not have a means to bond the neutral bar properly or clip in the main breaker.

A way to solve having a nonservice rated panel delemma is what you mentioned. Add a 100 amp breaker style disconnect ahead of that panel and make that panel a sub panel.

If you do this then you must marry the neutral and grounding bars in that main breaker style disconnect. Then you must separate the neutral and ground bar in that sub panel now being fed through that main breaker disconnect.

Here we go again, confusing, ain't it ?

Wg

re: Detached Garage sub-panel	Reuben	7:26 am tuesday september 11, 2001

Thanks for all your help!

My panel is service rated. It tells me to buy retaining kit #PK2MB for a breaker used as a main.

This forum has been a Godsend for me.

Thanks again!

re: Detached Garage sub-panel	Warren Goodrich	6:08 pm tuesday september 11, 2001

Glad to be of help to you. We hope you good luck with the rest of your project.

Wg