detached garage

[angryhalfinch]

Forgive Me if this is a topic already discussed. I've been searching the forum for answers to My question but can't seem to find exactly what I need.

My parents are selling there 100 some year old house. About 15-18 years ago, My Grandpa ran a 4-wire feed out to there detached garage. He installed a small 6 circuit panel in the garage. The home inspector told My parents that the garage needs a main disconnect and that it was not properly grounded. Isn't that 4-wire system an approved method 15-18 years ago? And with the 6 circuit panel in the garage I shouldn't need a main disconnect due to the 6 disconnect rule, right? The one thing I did notice in that panel, that the home inspector did not, is that being a sub-panel the ground and the nuetral should have been seperated. Now My colleages tell Me that I still need a ground rod (2 because of the Wisconsin supplement) but then that would create a redundant ground witch I always thought would be a violation too.

With all due respect, please don't answer my question with a simple article reference. I have a code book in front of Me right now but it seems rather unclear to Me.

 

[iwire]

Every separate building or structure supplied with a feeder or more than one branch circuit requires a grounding electrode system. 250.32(A)

The panel could use the 6 throws of the hand rule if it was listed for service equipment without a main. 225.33 and 225.36.

The disconnecting means at the garage will have to be at least 60 amps. 225.39(D).

All 2005 NEC references.

 

[paul]

With a 4-wire system, you're tying the ground rods into the ground bar only. The neutral bar should be isolated all the way back to the main panel. 250.32(B)(1) covers this. As to whether or not you need 2, then WI rules supersede the code, which says only 1.

As for the disconnect and/or main, 225.33 allows you up to six disconnects.

 

[augie47]

As for the disconnect and/or main, 225.33 allows you up to six disconnects.

BUT, 408.16 requires a Lighting panelboard have no more than two main breakers and in all probablility this is calssified as a L & A panel.

 

[don_resqcapt19]

augie,

BUT, 408.16 requires a Lighting panelboard have no more than two main breakers and in all probablility this is calssified as a L & A panel.

That is not exactly what the code section says (section moved to 408.36 in 2005 code).

408.36 Overcurrent Protection
(A) Lighting and Appliance Branch-Circuit Panelboard Individually Protected Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.

As long as the feeder OPCD has a rating equal to or less then the panel rating, the panel is protected. There is no requirement that the panel overcurrent protection be installed in the panel itself.
Don

 

[augie47]

panel

panel

thank you, don. i stand corected. i was aware of the "remote"
location rule, but for some reason, did not think it applied when a seperate building was involved. I should have read 225 closer.

 

[angryhalfinch]

According to atricle 225.30 a multiwire branch circuit is considered a single circuit. And if it is a garage or out building on residential property, you are allowed to use snap switches per article 225.36 exception. So the 6-circuit panel should meet and exceed this requirement, right? If I drive my 2 rods and seperate the grounds and nuetral then where does the ground from the 4-wire system go? I thought you can't create a redundant ground.

 

[Dennis Alwon]

If I drive my 2 rods and seperate the grounds and nuetral then where does the ground from the 4-wire system go? I thought you can't create a redundant ground.

If you have a 4 wire feeder then the neutral and ground must be separated and the #6 ground from the rod would be put on the ground bar.

 

[angryhalfinch]

This would make it redundant to the grounding electrode system for the main service, via the #10 ground in the 4-wire system.

 

[Dennis Alwon]

This would make it redundant to the grounding electrode system for the main service, via the #10 ground in the 4-wire system.

I am not sure what article you are thinking about. There is a GEC and a ground wire. This is legal.

 

[Psychojohn]

This would make it redundant to the grounding electrode system for the main service, via the #10 ground in the 4-wire system.

I live in Wisconsin, and at training for the 2005 code several years ago, we got in to a discussion on this subject with the instructor. He said that if a GEC is supplied from the main to the sub of a detached building, the ground electrodes conductor at the detached building and the GEC from the main both have to be connected to the ground bar at the subpannel, but isolated from the neutral.

 

[George Stolz]

This would make it redundant to the grounding electrode system for the main service, via the #10 ground in the 4-wire system.

Paths through the earth are not considered a parallel path for ground fault return current, they're acceptable. (Edit to add: Actually, with a continuous metal pipe between the two structures, the #10 EGC would be in parallel with the water pipe, and that's okay too. Parallel neutral paths along EGCs and grounding electrodes are prohibited.)

Here's a link to the FAQ on this topic if you're interested.

 

[sparky_magoo]

augie,

That is not exactly what the code section says (section moved to 408.36 in 2005 code).

Don

Thank you, I was reading about switchboards in damp locations when I saw your post.

 

[iwire]

According to atricle 225.30 a multiwire branch circuit is considered a single circuit.

Yes.

And if it is a garage or out building on residential property, you are allowed to use snap switches per article 225.36 exception.

Yes.

So the 6-circuit panel should meet and exceed this requirement, right?

No.

You garage is not supplied by a single or multiwire branch circuit, it is supplied by a feeder and must have a disconnecting means that is at least 60 amp rated.

I am not sure where you got the idea 'redundant' grounding electrodes are a code violation.

The NEC allows as many grounding electrodes as you want and they can be connected to the equipment grounding conductor at any point.

In this case the NEC requires additional grounding electrodes at separate buildings or structures.

Go buy a cheap 60 amp service rated main breaker panel swap it out and be done with it. :smile:

 

[angryhalfinch]

It seems to Me that I'm getting conflicting answers. I do highly appreciate the input from everyone. Being stuck at the same industrial location for the first 6 years of My career (total a 7.5) I haven't had much experience in the residential world. The way I read it, iwire and georgestolz have conflicting answers.

 

[George Stolz]

I don't think we do - what conflict do you see?

 

[angryhalfinch]

I was referring to the link that you posted. It seemed to me that it agreed with the fact that it is a branch circuit not a feeder. I did fail to mention that it is fed from a 40amp breaker from the house panel. Does this change anything?

 

[chevyx92]

I did fail to mention that it is fed from a 40amp breaker from the house panel. Does this change anything?

Read post # 2 again.

 

[suemarkp]

You garage is not supplied by a single or multiwire branch circuit, it is supplied by a feeder and must have a disconnecting means that is at least 60 amp rated.

What is the rating of the disconnecting means if you have more than one (no single main, either two or up to six)? Must each be 60, or can you have two 30's? How about six single pole 15's?

 

[George Stolz]

Let's go back to your first post.

The home inspector told My parents that the garage needs a main disconnect and that it was not properly grounded. Isn't that 4-wire system an approved method 15-18 years ago?

The four-wire system is still an approved method today. In the next cycle (2008 NEC), all new detached structures will even be required to have an equipment grounding conductor (EGC) installed with their feeders.

Think of the "EGC / no-EGC" decision as an entirely seperate aspect of the installation than the grounding electrode requirement. 250.32(A) is step one in a two-step process. There is one thing that determines whether we need a grounding electrode system (GES): Is the structure supplied by more than one branch circuit, or a feeder? If this is true (several branch circuits, or a feeder) then a GES is required.

Now, move on to step 2: Should we install an EGC with the feeder, or are we required to? In your case, grandpa made that decision 15 years ago, he installed an EGC. So, the GES required in step 1 is required to be connected to that EGC. The neutral is kept seperated from the EGC and the GES, and none of the surface metal of the electrical system comes into contact with a neutral until you trace it back all the way to the service disconnect of the originating building.

And with the 6 circuit panel in the garage I shouldn't need a main disconnect due to the 6 disconnect rule, right?

This is trickier than it seems on the surface. 225.36 requires the disconnect in a detached structure to be suitable as service equipment. See the Six Handle Rule FAQ to see why this requirement will most likely require a single main be used in the panel.

The one thing I did notice in that panel, that the home inspector did not, is that being a sub-panel the ground and the nuetral should have been seperated.

You're right, seperate them and test for continuity between the two, to be sure the service and EGC of the feeder are properly bonded at the beginning.

I was referring to the link that you posted. It seemed to me that it agreed with the fact that it is a branch circuit not a feeder. I did fail to mention that it is fed from a 40amp breaker from the house panel. Does this change anything?

I believed the entire time that there was a large breaker at the house, and smaller breakers (probably 15's or 20's) in the subpanel at the detached structure. Thus, the conductors running between the two buildings are a feeder. Feeders to detached structures kick in the requirement that all grounding electrodes present at the detached structure be used (250.32(A) leads you to the requirements in 250.50, just like a service.)

The only difference between this detached garage's panel and a normal service panelboard is that there is an EGC supplying it, so no neutral/EGC bond is permitted in the subpanel, and the GES is connected to the EGC, not the neutral. Otherwise, they look identical.

Hope that helps,