60AMP Subpanel detached garage

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Old 01-24-08, 09:37 AM
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60AMP Subpanel detached garage

Hey all:

Some electrical questions for a 60amp subpanel in my garage which is 30' from my home. There is existing piping from the house to the garage (roughly 5" diameter) which housed my old wiring and a water line. I was able to run PVC conduit inside the existing piping to carry the wiring to the subpanel. My questions are:


1. For a 30' Connection, will 4 #6awg (THWN) wires be sufficient, or do I need #4? 4 wires consisting of 2 Hots, 1 Neutral, 1 GND.

2. What size main breaker in the subpanel, I am assuming any breaker greater than 60AMP will work? Considering there will be 3-4 total circuits, likely at some point including a 220 circuit.

3. How to ground the subpanel. Can I run a gnd connection from the subpanel GND bus bar and tie it to the water pipe? Do I need to use a ground rod? Do I need to run a GND line from the main panel?

4. Should there be any connection in the subpanel between the GND bus bar and the NEUTRAL bus bar? Does this include not installing a bonding screw? Why or why not?
 
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  #2  
Old 01-24-08, 10:10 AM
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Originally Posted by bpgordy View Post
For a 30' Connection, will 4 #6awg (THWN) wires be sufficient, or do I need #4? 4 wires consisting of 2 Hots, 1 Neutral, 1 GND.
#6 is sufficient for the hots and neutral. The ground may be #10.

What size main breaker in the subpanel, I am assuming any breaker greater than 60AMP will work? Considering there will be 3-4 total circuits, likely at some point including a 220 circuit.
The main disconnect breaker in the subpanel should be no larger than the max rating of the panel. A disconnect breaker is actually not required at the subpanel if you have 6 circuits or fewer.

How to ground the subpanel.
Run the #10 ground from the house panel ground bar to the ground bar in the garage panel. Outside of the garage, drive a 5/8" x 8' copper-clad ground rod flush to the earth. Run bare #6 copper wire from a brass acorn clamp on the ground rod to the ground bus in the subpanel.

Should there be any connection in the subpanel between the GND bus bar and the NEUTRAL bus bar? Does this include not installing a bonding screw? Why or why not?
There should be no connection between the ground and neutral in the subpanel. This requires you to either remove or not install the bonding screw and usually to buy an add-on ground bar kit so ground and neutral have separate bars.

The why is a very complicated answer, but the gist of it is that ground and neutral may only be bonded at one place in the electrical system and that place must be the main panel.
 
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Old 01-27-08, 08:40 PM
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Thanks for the response. Home depot didnt have the wet rated wire or UF. Can I use standard 6AWG wire in conduit? What if I limited myself to 50amp? This will be in conduit from my house to the garage.
 
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Old 01-28-08, 05:42 AM
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I am sure that the store you mention had THWN wire. If not, try another store or an electrical supply store.

You must have waterproof wire. Underground conduit is a wet location, as it will fill with water.
 
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Old 01-28-08, 10:07 AM
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Look closely at the THHN (dry rated) wire they sell. It will also have a THWN-2 (wet) rating printed on the wire itself even if it's not advertised as such. Virtually all, if not all, THHN is dual rated as THWN-2.
 
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