Sub/sevice/load centr installation

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  #1  
Old 12-31-04, 08:45 AM
kmac01
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Sub/sevice/load centr installation

I am looking for advice on installing/grounding a “panel” in my attached garage of my raised-ranch. I say “panel” because I have heard “service panel”, “sub-panel” and “load center” to describe the metal box that I plan to attach to the wall in my garage. The reason I’m doing this is because I’m in the process of finishing off my basement where the Main panel is located and would have a rather difficult time adding circuits later if I wanted, due to the wall being finished around the main box. The box I have in hand is a Murry 60 amp main lug load center that reads “single phase, 3 wire, 120/240V AC. Not sure if this is what I really want?
Here’s what I’m thinking:
I want to run 30 amps out to the garage. I would use 10/3 + gnd for feeder. I would use a 2-pole 30 amp CB at my main panel. Now the question…how do I ground the panel in the garage? The box I have in hand does not have a ground bus included nor do I think it is meant to accommodate one. Shouldn’t this panel have its own separate ground bus? If so, then I need a different box, right? Lastly, I’ve seen talk about a ground rod / water pipe, etc. Does this apply for my lay out?

Any help would be greatly appreciated.
 
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  #2  
Old 12-31-04, 09:45 AM
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kmaco1,

Sounds like you are on the right track. Here is the benefit of my thoughts and what I would do.

There are numerous ways to identify "that box that gives you electricity". I normally call the main service panel just that; service panel. You don't say what your main service is rated at but my guess is it's 200 amps.

Next you want to put "electricity" in your garage. From your description of how much you want and what you have it sounds fine. Make sure your wire integrity is rated for how you plan on routing ie all indoors, partly outdoors, buried, etc. With the 4 conductor you will carry your ground back to the main panel which is good. I would use a 30 amp 2 pole breaker in the new sub panel as well as the main service panel.

I call the panel you want to use in the garage a "sub-panel" and it is "sub- fed" from the main service panel.There should be instructions in this 60 amp sub panel. There will be a place to connect your ground wire. Yes, it IS meant to accommodate a ground wire. There should also be a bonding conector that needs to be fastened from the neutral bar to the box itself to bond it. There is a screw hole there for it. These are very important. With your new sub panel grounded back at the service panel you should have the grounding issue covered-if, of course, your main panel is properly grounded and I bet it is. Don't ground anything to a water pipe, gas pipe, etc.

Next all you need to do is run your ckt plan in your garage, connecting everything back to your new sub panel-and make sure all is properly grounded. For more help the guys at your local supply house can be a valuable resource for local codes and information.

Another thought, with doing all this work---if you think you may EVER decide to have more capability out there in that garage, now is the time to upsize your wire and breakers accordingly. With that 60 amp sub panel you are not using it at full capacity-and you could set up that potential now for a % of what the overall cost of this project may be.

jm2c
 
  #3  
Old 12-31-04, 03:31 PM
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>>There will be a place to connect your ground wire. Yes, it IS meant to >>accommodate a ground wire. There should also be a bonding conector that >>needs to be fastened from the neutral bar to the box itself to bond it. >>There is a screw hole there for it.

If I am reading this correctly you are instructing kmac to place bond jumper in "sub-panel". This jumper should NOT be installed. In the sub panel all the electrical grounds (neutrals) are isolated from equipment grounds (green or bare).
 
  #4  
Old 12-31-04, 03:42 PM
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As up-n-running says, you must purchase and install a grounding bar kit, you must not bond the neutral bar to the panel, and you must not install a grounding rod or make any connection from your subpanel to any pipes.

Are you sure 30-amps is enough? Why not use 6/3 and get 60 amps?
 
  #5  
Old 12-31-04, 05:09 PM
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Sorry for any confusion on the sub panel bonding issue.

I was taught that in a residential service the first means of shutting off the service-whether that be a disconnect by the meter or the main panel itself-must be bonded by means of the green screw supplied for that purpose.

I was also taught (in a sub panel) to bond the neutral bar to the panel with the hardware (that little flat jumper clip) supplied for that purpose.

I'm always open to learn anything new, especially in this field, and I have by monitoring this forum. Shed any further lite on this anyone?
 
  #6  
Old 12-31-04, 05:42 PM
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trs4594, your advice is correct for some circumstances, but not those of kmac01. In kmac01's case, the garage is attached, so the neutral must not be bonded. For subpanels in detached structures, the neutral is bonded for a 3-wire feeder and unbonded for a 4-wire feeder. Of course, a 3-wire feeder is only allowed if there are no other metallic paths between the structures.
 
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