2 grounds in same conduit

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  #1  
Old 09-25-07, 09:23 AM
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2 grounds in same conduit

Presently,
The conduit from my main panel to my pool pump timer has 110v supply wires( blk, wht, grn) for the pool light and it has 220V supply wires (red,red,grn) for the pool pump. All in the same conduit going to the same place, the timer. Each supply has a separate breaker on the main panel. All wires are singles.

Since I'm now adding a spa/pool subpanel I would like to know if I should keep the 2 separate grounds when I change the 220V supply wires to a heavier gauge?

Or Can I just pull one big ground and remove the 2 small ones?

Possible reason for 2 grounds: there is a GFCI outlet on the light circuit in the timer box to protect the lights as loads only. But presently the 2 small grounds are connected to the same timer box ground bar.

Should I have an isolated ground wire from the main panel just for the GFCI outlet when I add the sub panel and have it only connect to GFCI outlet not to the timer or sub panel ground bars?

Thanks, Glenn
 
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  #2  
Old 09-25-07, 09:33 AM
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You have two grounds because someone mistakenly ran a second one, not understanding what they should have done.

In conduit, you run ONE ground wire, sized for the largest circuit. Sp if you have a 20 amp (12 gage wire) circuit and a 15 amp (14 gage wire) circuit, you r ground wire must be 12 gage wire.

The problem with running and connecting two grounds is that you could end up with more fault current running on a ground wire than the ground wire can handle.

Forget everything you ever heard about isolated grounds in a residential environment.

You need a single ground wire, sized for your sub panel feed.
 
  #3  
Old 09-25-07, 10:09 AM
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Bob,

Great, thanks,

Glenn
 
  #4  
Old 09-25-07, 11:13 AM
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If I recall from your previous questions, the pool subpanel is 70A with #6 THWN. This means the ground for the subpanel feeder needs to be at least #8 THWN green copper (bare copper is not allowed for a pool feeder, FYI).
 
  #5  
Old 09-25-07, 12:23 PM
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Ben,

Good, thats what I bought. insulated green THHN T90C 8ga to go with 2 red 6ga THHN T90c wires.

I forgot to get the 6ga neutral white.

I don't plan use any 110V breakers in the sub panel so the neutral won't be needed. But I thought I'd run it for future 110V sub panel use.

The pool lights have their own supply from the main panel, 12ga blk, 12 ga wht, 12ga grn(grn soon to be replaced with the 8ga grn).

Can I do the same idea with the white neutral wire as with the grounds by only running one 6ga white neutral that is used by the sub panel future expansion and by the lights?

To summarize, the conduct from the main panel would contain:
2 red 6ga wires for 220V lines
1 grn 8ga wire for sub panel, timer, pool lights, GFCI outlet ground.
1 black 12ga wire for pool lights.
1 white 6ga wire for neutral of pool light and future subpanel 110V use.

Thanks, Glenn
 
  #6  
Old 09-25-07, 12:49 PM
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Originally Posted by Glenn111 View Post
Can I do the same idea with the white neutral wire as with the grounds by only running one 6ga white neutral that is used by the sub panel future expansion and by the lights?
Absolutely NOT. The neutral for any circuit needs to stay with the hot wire(s) for the circuit.
 
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Old 09-25-07, 01:10 PM
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Just to be clear.(I hope)

The 120V light ckt stays as is.(remove the 12 grd) Run #6 white out if you want, BUT don't use it for the light.
The #6 grd is the new grd for everything as stated earlier.

In the Future, If this turns into a sub panel, then the lite ckt can come from it and the nuetral and power will derive from that panel.
 
  #8  
Old 09-25-07, 01:37 PM
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Leave the #12 hot and neutral for the pool lights as-is. Only the ground is shared with the subpanel.

If you plan to use this subpanel for only the 240V heater and pump motor, then you do not need the #6 neutral. As such, I would recommend that you save your money and not install the #6 neutral at this time. It would be a good idea in this case to put a label on or in the subpanel which states "No neutral present - 240V loads only".

If however, you want to use this subpanel to power 120V loads like a general-purpose receptacle or outdoor lightning then you should install the #6 neutral.
 
  #9  
Old 09-25-07, 02:06 PM
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Ok, Great, Thanks.

I'll have to decide on whether to make the sub panel box 240 only or capable of 120.

I'm leaning toward putting the Label "No Neutral Present - 240V Loads Only" on it.

Can't wait for this project to be over!

Panel is already mounted and plumbing is done.
Just have to pull 40ft of wire and move the 350lb heat pump from my garage to the pad.

Sure glad you guys here, cause they didn't teach this stuff at my school.

Thanks for all the help,

Glenn
 
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