Pull Box Grouding/Bonding , Other?

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  #1  
Old 11-01-13, 09:55 PM
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Pull Box Grouding/Bonding , Other?

I had the main service panel on my upgraded a year back. the electrician installed a 1.5" Flex metal conduit up the attic to allow for future circuits.

I had to install a "pull box" and he said i was good to go... so i am stumped already..

i bought a 10x10 metal box and connected the 1.5" flex conduit to the box. but realized i might have a grounding or bonding requirement.

What is needed in such a box to meet code?

1) my first circuit will be a 12gu 3- wire (3 loose wires THHN) pull from the service panel to the box; then connect these wires to romex and complete the new run to a bathroom.

- do i need to do nothing? and just continue to teh run on to where i am going?
install a dedicated wire to ground the box? install a grounding bar in the box and connect all future grounds to this bar?..etc?

thanks!

Erik
 
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Old 11-01-13, 10:17 PM
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NEC rules may differ but the CEC requires a bond wire in flex longer than 1.5 meters.
Is the flex connected to your service panel?
If so run a #12 bond from the ground bar of your panel up to your 10x10.
I like your 10x10 ground bar idea, but it isn't necessary. I would personally though as it makes things tidier in the box.
 
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Old 11-01-13, 10:32 PM
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1) my first circuit will be a 12gu 3- wire (3 loose wires THHN) pull from the service panel to the box;
What is the function of these three wires? hot/neutral/ground or two hots and a neutral?

install a dedicated wire to ground the box? install a grounding bar in the box and connect all future grounds to this bar?
We have a winner!

I would use 10 AWG for the ground wire.

Remember that if you pull more than three current-carrying conductors in a single raceway you must derate the conductors. All of them. So you need to plan all of your pulls and figure the wire sizes needed before making your first pull.
 
  #4  
Old 11-01-13, 11:16 PM
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Thanks

So, i should be good with some #8 THHN left over from another project?
a) use a run of #8 from the service panel to the ground bar --
b) then a ground wire from the ground bar to the box
c) then connect my new circuit ground pigtail to the ground bar?

Regarding de-rating - thanks for the reminder;
Does the size of the conduit affect the derating %?

I am thinking i may need to run
1- 20a run for this new BR
4-5 20a runs for the new kitchen
1- 220 or 50 amp run for the kitchen oven

the 20a runs would be 5x3 conductors = 15
plus 4 conductors for the oven

Looks like i need to de-rate at 50%? if so, i guess i need to run #10 to the pull box; then connect to my #12 romex to maintain the 20amp rating ?

Thanks!
Erik
 
  #5  
Old 11-01-13, 11:32 PM
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Your box ground bar should be attached to the box, so the bond from the bar to the box shouldn't be necessary. You may need to screw lugs onto the ground bars to accommodate the #8.
Your leftover #8 is perfect if you're planning to run a 50A stove to the 10x10.
Think of your bonding size this way...
You have a 20A circuit. #12's attached to a 20A breaker. In the event of a short circuit, your breaker will allow at least 20A to flow before tripping. Therefore the bond wire will be dealing with at least 20A of current in it. So you want a bond that can handle 20A. Match your bond with the highest ampacity in the box.
And for your bond run...
Panel (Lug or bar) > 10x10 (Lug or bar) > attached loomex grounds to bar.
 
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Old 11-02-13, 05:55 AM
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Since the wires will be smaller than #4 they should be in the proper colors.
 
  #7  
Old 11-02-13, 08:21 AM
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the 20a runs would be 5x3 conductors = 15
plus 4 conductors for the oven
Since you are mounting a ground bar in the 10 X 10 box and bonding to the main panel with #8, you don't need to run a ground wire from each individual circuit all the way back to the main panel. The branch circuit grounds from your NM cables will terminate in the ground bar.

So......the 20A runs would be 5 X 2 conductors = 10
plus 3 conductors for the oven.
 
  #8  
Old 11-08-13, 03:01 PM
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Smile Common Ground?

Thanks for all the replies

I like the idea of running a common ground to the pull box to help find the maximum conductor fill given then derating factors.

Is it code in LA (California) to run say a common #4 ground wire to the ground bar (even with derating of 50%) that would give me 47.5Amp (95 Max *.5)

Then just run the hot/neutral in the conduit to save space?

if so, this would solve my issues for not having enough space.

Thanks!
ERik
 
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