Wiring for New Detached Garage

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jeff48356

Senior Member
Suppose someone is considering building a new detached garage in Livonia, Michigan. The house currently doesn't have any garage at all. I have a couple of questions:

1) Someone once mentioned something about the minimum height of wires ran perpendicular to the framing. It was something to the effect that it's OK as long as the walls were to be covered with drywall, but if left open, the wires need to be at a certain minimum height. Do you know what the code says on that?

2) For the underground electric feed to the garage, can Romex cables be run inside of PVC conduit, or would these need to be individual THHN conductors terminated at junction boxes (one in the garage, one in the basement near the service panel)?
 

Cavie

Senior Member
Location
SW Florida
Suppose someone is considering building a new detached garage in Livonia, Michigan. The house currently doesn't have any garage at all. I have a couple of questions:

1) Someone once mentioned something about the minimum height of wires ran perpendicular to the framing. It was something to the effect that it's OK as long as the walls were to be covered with drywall, but if left open, the wires need to be at a certain minimum height. Do you know what the code says on that?

2) For the underground electric feed to the garage, can Romex cables be run inside of PVC conduit, or would these need to be individual THHN conductors terminated at junction boxes (one in the garage, one in the basement near the service panel)?


1. Local code maybe.

2. No. Wet location
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I can't speak for Michigan as jurisdictions often address the wiring of detached garages differently. Based on 334.10 some require a 15 min fire rated finish and some consider the garage as part of the dwelling and don't require the NM to be covered.
Where left exposed, 334.15 requires the NM to follow the building surfaces.
Many jurisdictions require the NM to run with the framing members or be protected by running boards where subject to physical damage. Often AHJs have an arbitrary height above which they do not consider the NM to be subject to damage. 8 ft is often the choice.

As far as NM in Conduit outside, it is prohibited by the NEC as clarified in ''08 by 334.12(B)(4) and 300.9
 

LEO2854

Esteemed Member
Location
Ma
Suppose someone is considering building a new detached garage in Livonia, Michigan. The house currently doesn't have any garage at all. I have a couple of questions:

1) Someone once mentioned something about the minimum height of wires ran perpendicular to the framing. It was something to the effect that it's OK as long as the walls were to be covered with drywall, but if left open, the wires need to be at a certain minimum height. Do you know what the code says on that?

2) For the underground electric feed to the garage, can Romex cables be run inside of PVC conduit, or would these need to be individual THHN conductors terminated at junction boxes (one in the garage, one in the basement near the service panel)?
It would be better if you ran a two pole circuit to the garage to a circuit breaker panel so you have a disconnect means for your garage.230.70 and a ground rod for the building
Then you can have a couple of circuits out there.
if no sheet rock you can use emt to hit your plugs and switches.
 
It would be better if you ran a two pole circuit to the garage to a circuit breaker panel so you have a disconnect means for your garage.230.70 and a ground rod for the building
Then you can have a couple of circuits out there.
if no sheet rock you can use emt to hit your plugs and switches.


If it is a feeder, Art 230 has no bearing on this.

In dwellings, typically installing a 3 wire circuit would make it so a ground rod would not be required. Work smart...

Augie, I myself would refrain from mentining an 8ft requirement, as that height requirement is for emerging from grade.
What I would say is the NM cable would have to be protected from physical damage, which may occur at any height. I tell guys to ask the particular inspector what he wants, as this is a 'subjective' requirement.

Also, attached garages are generally considered part of the dwelling unit, and detached garages are treated separately. We discussed this just this past weekend at the Eastern Section Meeting.
 

kwired

Electron manager
Location
NE Nebraska
Wouldnt running the romex through bored holes in the framing be considered protected from physical damage?

If the framing gets a covering such as drywall yes, if no covering the cables are still exposed, many disagreements as to whether they are protected in this case.

My opinion, if they are exposed they are subject to physical damage.

Now read through 334.10, if not part of a dwelling and not covered by at least a 15 minute finish NM cable is not permitted to be used.
 
If the framing gets a covering such as drywall yes, if no covering the cables are still exposed, many disagreements as to whether they are protected in this case.

My opinion, if they are exposed they are subject to physical damage.

Now read through 334.10, if not part of a dwelling and not covered by at least a 15 minute finish NM cable is not permitted to be used.

Lets take this a step further.
Are you saying that 'exposed' is the same as 'subject to physical damage'? Take a look at 334.15. Notice there are no height requirements in this section.
Think of UF installed outside on the surface of a structure about 6ft above grade.
Is it exposed?
yes,
Does this mean it is subject to physical damage?


Because, if you do, then NM cable that is installed within the cavity of a suspended (drop ceiling)[where permitted by code] would not be permitted, as a drop ceiling is considered exposed. (see the definition in Art 100)



*Physical damage and Subject to physical damage are not defined in the NEC.
 
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hurk27

Senior Member
Here in Indiana detached garages are considered part of the dwelling, and are treated as covered under the one and two family dwelling codes in the IRC, here if there is a wall finish on at least one side of the studs there is no restrictions, but if in open studs like support walls around a basement stairway, they can only run down vertically to the box, but not across through bored holes, so like it was said, its up to your AHJ, I'm only a few miles from the Michigan line, and I have never had a desire to work up there, from what I was told if I get a Michigan masters, I can't do any work, so how can you work as a sole proprietor?

Well I agree with Pierre, if not allot of power is needed then just run a multi-wire circuit to the garage, no grounding electrode needed and simple.

But if your needing a few circuits, the two options I use is, double lug meter base back unto the ground with a 3-wire from this meter (SEC's not feeders), over to the garage and up and LB into the back of a main breaker panel which you would have to install anyways, wire the house back to the other set of lugs in meter, third option is 4-wire feeders from the house panel, to the garage, and still have to hit a main breaker panel, also with these two last options grounding electrodes are required.

But all methods require any wire in a wet location pipe or no pipe has to be wet location listed.
 

kwired

Electron manager
Location
NE Nebraska
Lets take this a step further.
Are you saying that 'exposed' is the same as 'subject to physical damage'? Take a look at 334.15. Notice there are no height requirements in this section.
Think of UF installed outside on the surface of a structure about 6ft above grade.
Is it exposed?
yes,
Does this mean it is subject to physical damage?


Because, if you do, then NM cable that is installed within the cavity of a suspended (drop ceiling)[where permitted by code] would not be permitted, as a drop ceiling is considered exposed. (see the definition in Art 100)



*Physical damage and Subject to physical damage are not defined in the NEC.[/quote]

Not being defined I agree with. In a garage or storage area everything exposed is subject to physical damage IMO. I have seen many times in garages where items are hanging from cables in walls or ceilings that are not covered. If I know the cable will not be covered I will not run it through bored holes across the studs especially at levels below 7 or 8 feet off the floor, but usually will not do it at all.

Installing EMT (especially 1/2 inch) is not necessarily as expensive as some may think it is, and is probably a better installation anyway. It takes time to bore all your holes for cable, 1/2 EMT is fast and easy to bend. EMT is an acceptable equipment grounding conductor, less time will be spent connecting EGC's if you don't run a separate conductor for it. Either install takes about the same amount of time and a fairly similar cost of materials. If installing multiple circuits the raceway method may actually take less time to install.
 

hurk27

Senior Member
Lets take this a step further.
Are you saying that 'exposed' is the same as 'subject to physical damage'? Take a look at 334.15. Notice there are no height requirements in this section.
Think of UF installed outside on the surface of a structure about 6ft above grade.
Is it exposed?
yes,
Does this mean it is subject to physical damage?


Because, if you do, then NM cable that is installed within the cavity of a suspended (drop ceiling)[where permitted by code] would not be permitted, as a drop ceiling is considered exposed. (see the definition in Art 100)



*Physical damage and Subject to physical damage are not defined in the NEC.[

Not being defined I agree with. In a garage or storage area everything exposed is subject to physical damage IMO. I have seen many times in garages where items are hanging from cables in walls or ceilings that are not covered. If I know the cable will not be covered I will not run it through bored holes across the studs especially at levels below 7 or 8 feet off the floor, but usually will not do it at all.

Installing EMT (especially 1/2 inch) is not necessarily as expensive as some may think it is, and is probably a better installation anyway. It takes time to bore all your holes for cable, 1/2 EMT is fast and easy to bend. EMT is an acceptable equipment grounding conductor, less time will be spent connecting EGC's if you don't run a separate conductor for it. Either install takes about the same amount of time and a fairly similar cost of materials. If installing multiple circuits the raceway method may actually take less time to install.


Heres what I tell inspectors at code meetings when this comes up.

When I hear of all the dangers of NM being exposed even when its inbetween studs, I tend to remind them of all the cheap little lamp cords laying around there house being stepped on, shut in doors, pulled on, tripped over.

It carries the same voltage as the NM, it carries the came current as the NM, most cases its under sized for the same circuit as the NM.

Yet we have no problem with this in anyway, we even expose our children to them although we do try to teach them not to play with these cords, but yet exposed NM in which only mostly adults would ever be around, we cry danger Will Roberts!:confused:

I don't get it, how far are we going to pad our world?:cool:
 
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lucky1974

Senior Member
Location
Michigan
Jeff, The electrical Inspector in Livonia is a good guy call him and talk to him. His name is Nelson.

1.) The garages I wire that aren't going to be drywalled, I drill the top plate and follow the finish of the 2x4. I dont run through bored holes horizontally. If I remember correctly that is his interpretation of not subject to damage.

2.) No NM isn't rated for a wet location.

Hope this helps
 

greenie

Member
third option is 4-wire feeders from the house panel, to the garage, and still have to hit a main breaker panel, also with these two last options grounding electrodes are required.

Would you be able to use a sub panel, not need a main breaker for this application if you have a feeder breaker in the house panel?

Wet behind the ears.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Would you be able to use a sub panel, not need a main breaker for this application if you have a feeder breaker in the house panel?

Wet behind the ears.

A separate structure requires a disconnecting means or CB's that require no more than "6 throws of the hand" for the sub panel. Usually a main CB in the sub is the simplest way to accomplish this.

Welcome to the Forum. :)
 
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