Subpanel Grounding

Reply

  #1  
Old 04-05-04, 05:35 PM
DANSKOTA
Visiting Guest
Posts: n/a
Subpanel Grounding

I recently added a 6 breaker subpanel in my laundry room. I have six 15amp breakers running outletts in my garage. The feeder to this panel used to go to a 220v outlet for the electric dryer, but I converted to natural gas, and so I used this 6/3 (1red, 1blk, 1white, and 1 exposed ground) copper wire fed by two 40amp breakers (bridged together for 220v) off the main panel.

Now I'm reading these posts that warn against combining the ground and neutral bars (which I did, since there wasn't a separate bar for ground). I now have 3 questions...

1) How is this any different than what is going on in the main panel only 15ft away...is it dangerous?, or just code.

2) If I mount a seperate ground bar, can this bar be touching the metal box? the current neutral bar is isolated by plastic.

3) Can I run a ground strap to the copper water pipes feeding the washing machine? Or do I have to drive a grounding rod.

Thanks in advance for your help. I have another ??? about a wire I ran to my metal shed, but I'll start a separate post for that.
 
Sponsored Links
  #2  
Old 04-05-04, 06:00 PM
BuzzHazzard
Visiting Guest
Posts: n/a
Re: Subpanel Grounding

Originally posted by DANSKOTA
I recently added a 6 breaker subpanel in my laundry room. I have six 15amp breakers running outletts in my garage. ...
Now I'm reading these posts that warn against combining the ground and neutral bars (which I did, since there wasn't a separate bar for ground). I now have 3 questions...
Six 15 amp breakers for a garage? That's a LOT. How many receptacles per breaker?

1) How is this any different than what is going on in the main panel only 15ft away...is it dangerous?, or just code.
The reason is because if you combine the ground and neutrals in your subpanel, any current returning to the main panel will now be divided between your neutral feed and your ground feed. You will have made your ground wire a current carrying conductor. The code is, by definition, for safety. The code is about safety,

2) If I mount a seperate ground bar, can this bar be touching the metal box? the current neutral bar is isolated by plastic.
It HAS to be touching the box. That's part of the idea, just like any metal outlet boxes must be grounded. The neutral bus bar is isolated by a plastic device by design for exactly this reason. Your neutral bus should have had a green scew or some type of metal strap to bond it to the box. In subpanel use, you would avoid doing this, but in main panel use you would intentionally do this.

3) Can I run a ground strap to the copper water pipes feeding the washing machine? Or do I have to drive a grounding rod.
Neither. Your subpanel should include two separate bus bars as described above--all neutrals tied to the insulated bus, and all grounds tied to the newly added ground bus.

Buzz
 

Last edited by BuzzHazzard; 04-05-04 at 06:13 PM.
  #3  
Old 04-05-04, 06:03 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Yes, combining the neutral and ground was a serious mistake. Luckily for only $5, you can buy a grounding kit and fix this problem in short order.

(1) The danger is limited to those 15 feet, and at the subpanel, but it is a danger nevertheless. Because you have current flowing on the grounding wire, your subpanel is not at ground potential, thus creating a shock hazard at the subpanel.

(2) The grounding bar must be touching the metal box. If the panel has a green screw bonding the neutral to the box, you must remove it.

(3) Neither. The subpanel is grounded through the grounding wire from the main panel, and no other way.
 
  #4  
Old 04-05-04, 06:18 PM
DANSKOTA
Visiting Guest
Posts: n/a
OK, thanks guys...

So I should go to Home Depot asap and buy a grounding bar for this subpanel. I should attatch it directly to the metal of the box, and remove any green grounding screw from the neutral bus. Then I should attach only the bare copper wires from the feeder and from the garage outletts to this grounding bar, but do not add another ground wire to water pipes.

As for what I use the six breakers for, 2 actually go to the garage and each feed 2 outlett boxes. I ran one outside to my flag pole using underground rated 12/2 to a weathertight duplex outlett. This lights my US Flag at night, and the xmas lights during the winter. Another goes to my metal shed (now Its really sounding dangerous...read my next post). One goes to my washer and dryer outlett, and the last is still empty.

I guess I'm lucky no one has gotten a jolt from this. Sounds like an easy fix, though. Maybe I'll just go turn it off now. Laundry can wait.

Thanks again!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes