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Old 11-14-2010, 12:24 PM   #1
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correct garage subpanel wiring


I have detached garage with 2 lines going into it from a subpanel in the house. There are no metallic connections between the garage and house other than the 2 lines. Line 1: 110 off a 20amp breaker that goes to the garage and directly feeds a couple of lights and electrical outlets. Line 2: 220 off a 30amp breaker that goes into a subpanel. This line has 2 hots and 1 neutral only (no ground). The subpanel does not have a grounding electrode. From what I have found, old code permitted a 3 wire feeder to a separate structure so long as there were no metallic connections between the 2 structures. But here, I also have the 110 wire connecting the 2 structures. Do I have a problem? Also, if I need to install a ground rod, where does that wire connect into the subpanel?
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Old 11-14-2010, 12:27 PM   #2
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correct garage subpanel wiring


Yes...you can only have:

1 circuit going to a detached structure
OR
a MWBC (2 circuits shared neutral)
OR
a sub panel

You can't have a MWBC & another circuit
You need a sub-panel if you need all 3 circuits
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Old 11-14-2010, 12:29 PM   #3
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correct garage subpanel wiring


yes, you have an improper installation. You can only run one circuit (which does include a multi-wire branch circuit (2 hots + the common neutral) to a detached building.

you ask a question about a subpanel but from what you have stated, you do not have a subpanel in the garage. Are you intending on installing a sub?
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Old 11-14-2010, 12:35 PM   #4
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correct garage subpanel wiring


Thanks. There is already a subpanel in the garage - the 240 connects to that, then that subpanel runs the pump for my well and a pressure pump for my well water holding tank. (the water pipe from the garage to the house is PVC). If I need both the 240 run and 120 run, can this all go into the subpanel?
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Old 11-14-2010, 12:40 PM   #5
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correct garage subpanel wiring


You can run only what has already been stated.

If you want to power the subpanel properly, you can take out of the subpanel any number of circuits for use in the garage.
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Old 11-14-2010, 12:43 PM   #6
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correct garage subpanel wiring


Sorry, can you please clarify? Would you suggest removing the 120 run from the house, leaving only the separate 240 run from the house. Then that 240 stays into the subpanel like it does now, but then connect the 120 run in the shed back into a new breaker in the subpanel?
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Old 11-14-2010, 12:48 PM   #7
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correct garage subpanel wiring


Is the 240 volt line going to a sub panel or a disconnect switch?
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Old 11-14-2010, 12:50 PM   #8
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correct garage subpanel wiring


The 240 goes into a subpanel that has a couple of spots left in it so I could put in a 20amp 120 breaker and power the garage lights and outlets from that. That subpanel, however, has no grounding rod connected into it, which I would have to do. (by the way, does the wire from the grounding rod go to the single bus bar in the subpanel?)
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Old 11-14-2010, 12:50 PM   #9
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correct garage subpanel wiring


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Originally Posted by lawsklsux View Post
Sorry, can you please clarify? Would you suggest removing the 120 run from the house, leaving only the separate 240 run from the house. Then that 240 stays into the subpanel like it does now, but then connect the 120 run in the shed back into a new breaker in the subpanel?
basically, yes but you may have a problem. What size of wire is the largest wire from the house to the garage? That will limit the size of breaker you can feed this subpanel with.

also, there must be a main breaker in the sub or a disconnect prior to the panel in the garage. is there one or the other?
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Old 11-14-2010, 12:53 PM   #10
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correct garage subpanel wiring


The wire from the house to the garage is 10 gauge off a 30amp breaker. Currently, there is no disconnect or main breaker on the subpanel in the garage.
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Old 11-14-2010, 05:28 PM   #11
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correct garage subpanel wiring


You are allowed up to 6 breakers in the garage panel without the need for a single main breaker. How many are there in yours?
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Old 11-14-2010, 09:26 PM   #12
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correct garage subpanel wiring


The panel has space for 8 but I only have 4 installed - 3 are 2-pole 240V and one is a 1-pole 120V. I have one breaker location left empty. Does that work?
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Old 11-14-2010, 09:38 PM   #13
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correct garage subpanel wiring


Yup. As long as you have 6 or less handles to throw ...
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Old 11-14-2010, 10:11 PM   #14
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correct garage subpanel wiring


does the feeder connect directly to the bus of the panel?
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Old 11-14-2010, 10:54 PM   #15
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correct garage subpanel wiring


The 2 hot feeders connect to the lugs at the top of the panel. The neutral feeder connects to the only bus bar. The bonding strap for the bus bar to the case is not attached - should it be?
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