50 amp 3 wire conversion to 4 wire

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  #1  
Old 03-11-16, 06:25 AM
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50 amp 3 wire conversion to 4 wire

I currently have a sub-panel (was used for a welder) with:
NEMA 6-50R (50A 240V)
Red & Black are Hot
White/neutral AND Bare/ground go to the SAME connection bar.

I want to replace that with a NEMA 14-50R (50A 240V)

I think all I need to do, is put a another connection bar. Then use 1 (existing) connection bar for the existing White/neutral and use the new connection bar for the bare/ground wire from the main box, from this new ground connection bar, I can run the Green wire that I need for the new NEMA 14-50R.

Sound right?

Basically, the old NEMA 6-50R is a 2-pole, 3-wire, with Ground & Neutral wired together. The new NEMA 14-50R is a 3-pole, 4-wire with separate ground & neutral, that;s the problem I'm attempting to address.

Thanks a lot!
 
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  #2  
Old 03-11-16, 06:51 AM
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At one time a panel in a separate building was viewed as a separate service and was allowed to be a 3 wire feeder (hot, hot, neutral). Now all feeders are required to have a separate ground.

It sounds like your sub panel does have a 4 wire feeder (hot, hot, neutral, ground) so I would recommend rewiring to current code. Install ground bar(s) and move all grounds there and if the neutral bar is bonded to the steel case, remove the bonding screw/strap.

Then wire your new 4 wire receptacle as you described with the ground and neutral wires to separate bars.

The new NEMA 14-50R is a 3-pole, 4-wire with separate ground & neutral
Still a two pole breaker, just a 4 wire feed.
 
  #3  
Old 03-11-16, 07:50 AM
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Is the subpanel in the same building as the main panel or is the subpanel in an outbuilding such as a detached garage or shop?
 
  #4  
Old 03-11-16, 09:12 AM
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This sub panel is in my attached garage.

Just to make 101% sure (I do that with electrical)
I have all 4 wires coming into the sub panel. It's just that the bare ground & white neutral are currently wired to the same ground bar.
So, I can:
1) Leave the existing ground wires on the existing ground bar.
2) Remove the white/neutral wires from the existing ground bar, and put them on a new connection neutral only connect bar, just make sure not to bond it to the sub panel.


Thanks!
 
  #5  
Old 03-11-16, 09:32 AM
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Although it's probably most common to do it the other way around...the existing buss becomes the neutral buss and the new buss becomes the ground buss, as long as you separate them and make sure the neutral buss isn't bonded to the box or the ground buss it doesn't matter which you use for which.
 
  #6  
Old 03-11-16, 09:38 AM
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1) Leave the existing ground wires on the existing ground bar.
2) Remove the white/neutral wires from the existing ground bar, and put them on a new connection neutral only connect bar, just make sure not to bond it to the sub panel.
It would be unusual for a box to have a ground bar, especially an older one. They just aren't sold that way. 99% likely the bar in your box is a neutral bar. Look to see if it is on insulators.

Assuming you have a neutral bar it is probably bonded with a screw through the bar or (less likely)a strap. The grounding means must be removed. You will add a ground bar using the pre tapped holes in your box.
 
  #7  
Old 03-11-16, 10:31 AM
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I'll have to look at the box again, but it only has 1 bar currently used for both the white/neutral & bare/ground, I believe it's mounted to a plastic (non metal) support that is then attached to the box. If that's the case, I could leave that for the neutral bar, and then attach my new bar to the box for the grounds?

Thanks again for your help, it's much appreciated.
 
  #8  
Old 03-11-16, 11:27 AM
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If that's the case, I could leave that for the neutral bar
Not could, should. It is the neutral bar. Doubt you could even buy anything but a ground bar. If a box comes with only one bar it is always a neutral bar.
 
  #9  
Old 03-11-16, 06:58 PM
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Install ground bar(s) and move all grounds there and if the neutral bar is bonded to the steel case, remove the bonding screw/strap.
Both Tolyn and Ray are right. Ground bars usually cost $10 or less and are readily available.
 
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