sub feeder panel installation

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  #1  
Old 04-05-06, 10:19 PM
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sub feeder panel installation

I was considering adding a subfeeder box in my home. i went to home depot to price everything out, the panel said that the grounding bus was not included. Do i need one? Can't i just use one of the two buslines in the box if the are seperated? If i have to add the Grounding bus, Does is matter where?
 
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Old 04-05-06, 11:24 PM
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> Do I need one?

Yes. And since you asked, you need to do some more studying.


> Can't I just use one of the two buslines in the box if they are separated?

No. They aren't.


> If i have to add the Grounding bus,

Yes, you do. They are not expensive.


> Does is matter where?

The manufacturer has holes pre-drilled where they go.
I always put one on the left and one on the right to keep the wiring neater. This way, wires don't have to go around to the other side to land.
It saves wire. But mainly, it reduces clutter and makes the job go faster.
 
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Old 04-06-06, 03:44 AM
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Originally Posted by dunka11us
the panel said that the grounding bus was not included. Do i need one? Can't i just use one of the two buslines in the box if the are seperated?
You must have _electrically_ separated ground and neutral bus bars in a subpanel.

Essentially all panels are supplied with a combination ground/neutral bus. In these panels you must add a ground bus kit and _remove_ the ground bonding from the neutral bus.

My understanding is that some panel manufacturers provide two separate bus bars, and that by removing jumpers you can make one a ground bus and the other a neutral bus. If the panel label permits this, then you can simply do so and not buy a ground bus kit. But in any case you must end up with 2 bars, one connected to the panel enclosure for equipment ground, and one isolated from the panel enclosure for neutral.

-Jon
 
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Old 04-06-06, 03:59 AM
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The question you pose depends on the type and brand of panel. Some panels have the ground and neutral busses tied together by a jumper of some kind that when removed provides a separate neutral and ground buss. Other types require a separate ground buss be installed for sub panel use. What is most important is that the bonding jumper used to tie the neutral to ground is removed as these must be separate in a sub panel.

The cost of the extra buss for grounds is typically around $10.00 or less and it will mount in holes provided by the manufacturer for the purpose.
 
  #5  
Old 04-07-06, 05:31 AM
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main panel

i took a look in my main panel, the neutral and ground are one in the same if i add a ground bus, what should i do for the all the Bx ? can i just run a piece for ground wire to the armor ? Or bond the box and that will be ok?
 
  #6  
Old 04-07-06, 06:07 AM
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_Properly installed_, the cable clamps which hold the AC cable (commonly called BX) provide the equipment ground connection. The box is bonded to the equipment ground bus, then the clamps screwed to the box, and finally the cable held tightly in the clamp.

You must take care that the connection between the clamp and the box is a good electrical connection as well as a good mechanical connection. This means that concentric knockouts can be a problem, and that you may need to remove paint around the hole. Be sure to use proper AC cable clamps, which are _similar_ but not the same as NM ('Romex') cable clamps.

My personal preference is that in situations where armored cable is required, I use MC cable, which has the metal armor, but also has a green ground wire, rather than trusting the armor as the equipment ground.

You mention that the ground and neutral wires go to the same bus in your main panel. This is correct. Ground and neutral are supposed to be connected together at _one_, and _only_ one location in your house. Generally this is in your main panel, though other common locations are at a meter-main or in the meter itself. In the panel where ground and neutral are connected, you may use a single bus bar for both ground and neutral wires. If you don't understand this detail of neutral bonding, then I strongly urge you to re-read your books on the topic.

-Jon
 
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