Minimum requirement for detached garage.

Status
Not open for further replies.
B

bth0mas20

Senior Member
Location
Maryland
The county I am wiring a detached garage for is following the 2008 NEC.
The customer would like to have the minimum service required to pass code.
I dont believe from what Ive read in the 2008 code that I can just run a 12/3 circuit to a double pole single throw switch and feed two circuits from that anymore. Im gathering that I will need to set a 60A panel with a gr rod and It dosent have to have a main if its less than 6 throws right. I would like it if I could run the 12/3 but I dont think I can.

If I do have to set a 60A panel can I just make it one ungrounded conductor 120v and feed a main lug panel with 2 breakers and a gr rod.
 
The cheapest electrical system is wireless :)

I think you can run 120V and use a 15A snap switch, put the lights on with the receptacles. Keep in mind if your customer prioritizes cheep over any thing else just oblige them with minimum. Put a few estimates together, one for best scenario, one for middle of the road, and one bare bones minimum, give these to your customer and let em choose.

You do have to install an electrode (250.32), just pick one from 250.52. Also in ?08? if you feed this building with 120/240 you must install a 4W circuit not 3W (250.32).
 
Well their is no need for 240v. He only needs a few lights and 2 outlets.
If I ran a 20a 120v circuit with a disc snap sw then to the lights and outlets. Would that work.
 
bth0mas20 said:
I dont believe from what Ive read in the 2008 code that I can just run a 12/3 circuit to a double pole single throw switch and feed two circuits from that anymore.
Click to expand...

You can use a DP 30A switch.

Often we provide a 50A feed, #6 NM to #8 THHN to sub panel (or #8 all the way). Just install the circuits needed without a main, if they add more than 6 the main can be provided at that time.
 
bth0mas20 said:
Well their is no need for 240v. He only needs a few lights and 2 outlets.
If I ran a 20a 120v circuit with a disc snap sw then to the lights and outlets. Would that work.
Click to expand...

Yep that will work, you can even install as a 15A but I believe the conductors underground must be #12's minimum.
 
Doesn't the exception in 250.32(A) say you can take a 12/3 multiwire branch circuit to the detached garage without the need for a grounding electrode?
Where are you getting the idea that it has to be a 20 amp circuit using a #12 wire?
 
Interesting olio of responses. Mine, in no particular order:

If you'll have both lighting and power outlets, I'd run a 3-wire MWBC; the labor is the same.

The 'minimum' is a single 15a circuit on #14. Being underground doesn't matter.

If power tools might be used, I might use #10, and I'd consider a small panel now.

If you want to future-proof it, install a 3/4" PVC conduit, which should be good up to 100a.
 
LarryFine said:
Interesting olio of responses. Mine, in no particular order:

If you'll have both lighting and power outlets, I'd run a 3-wire MWBC; the labor is the same.

The 'minimum' is a single 15a circuit on #14. Being underground doesn't matter.

If power tools might be used, I might use #10, and I'd consider a small panel now.

If you want to future-proof it, install a 3/4" PVC conduit, which should be good up to 100a.
Click to expand...

Not sure about 3/4" being good for 100a.

How did you calculate that?

I get about 50a:-?
 
petersonra said:
Is there any requirement that a garage have electricity at all?
Click to expand...
No there isn't but, when you do supply it with electricity it must have atleast one lighting out and receptacle.

Roger
 
Last edited:
roger3829 said:
Why would conductors for a 15amp circuit need to be #12??
Click to expand...

Da-no, for some reason I thought conductors underground minimum were #12. I'm looking in Article 300 and don't see it, must have been a spec.
 
jshaw said:
Doesn't the exception in 250.32(A) say you can take a 12/3 multiwire branch circuit to the detached garage without the need for a grounding electrode?
Where are you getting the idea that it has to be a 20 amp circuit using a #12 wire?
Click to expand...

Yes your correct!
 
250.32 does not require a grounding electrode if you use a single branch circuit. a MWBC is considered a single branch circuit. 250.32 except.
 
Last edited:
tryinghard said:
No you still have to ground the separate building as per 250.32
Click to expand...
there is exception to A250-32, saying a grounding electrode shall not be required where only a single branch circuit, including a mwbc, supplies the the building or structure. the branch circuit has to include an equipment grounding conductor. so i would have to say u don't need to have a grounding electrode at the separate building.
 
tryinghard said:
The cheapest electrical system is wireless :)

I think you can run 120V and use a 15A snap switch, put the lights on with the receptacles. Keep in mind if your customer prioritizes cheep over any thing else just oblige them with minimum. Put a few estimates together, one for best scenario, one for middle of the road, and one bare bones minimum, give these to your customer and let em choose.

You do have to install an electrode (250.32), just pick one from 250.52. Also in “08” if you feed this building with 120/240 you must install a 4W circuit not 3W (250.32).
Click to expand...

Just to be clear. A Grounding electrode is not required for a single circuit. See the exception to 250.32. This inculudes a MWBC.

Also see Art 225 Outside branch circuits and feeders

Edit....Had I continued to read the thread I would have known they already said that.
 
Last edited:
Thanks for all of your responses.

The install that ive decided on:

Single 30a circuit out of the house panel. Then 60ft of 10-2 uf underground to the detached garage. Up the side of the garage sleeved in pvc thru the wall to a 4 space panel (only 120v no 240v). No grounding electrode. One circuit fed by a 15a arc fault bkr for 4 medium base lights total. Then a 20a breaker to a GFCI protected outlet circuit with 4 outlets.

I probally put more info than was needed to explain this. I feel that this will be sufficient to pass code.
 
bth0mas20 said:
Thanks for all of your responses.

The install that ive decided on:

Single 30a circuit out of the house panel. Then 60ft of 10-2 uf underground to the detached garage. Up the side of the garage sleeved in pvc thru the wall to a 4 space panel (only 120v no 240v). No grounding electrode. One circuit fed by a 15a arc fault bkr for 4 medium base lights total. Then a 20a breaker to a GFCI protected outlet circuit with 4 outlets.

I probally put more info than was needed to explain this. I feel that this will be sufficient to pass code.
Click to expand...
If you run 10/2 UF and install a panel with 4 breakers than you need a ground rod or 2.

Edit to add or 2 ground rods.
 
Last edited:
Status
Not open for further replies.
Top