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| Subject - Bonding J-box | |
| David Hyatt | If you have a metal J-box box with PVC entering in, the ground is say a 2/0. How do you bond the box? Run a separate ground to the box? Maybe run a smaller gnd off the spliced 2/0? What size would it have to be? Could you use a #10? |
| Ryan_J | It has to be sized baserd on table 250.122 |
| David Hyatt | So if the box contains 200 amp circuit (feeder circuit). I would have to use #6 copper. Could that be spliced off the 2/0 gnd or do I pull a separate #6 from somewhere else? Regardless the box has to be bonded. |
| lctrc789 | One of two things perhaps you could use a PVC box rather then a metal one or install bond bushings and make a small loop so that you could bond with a # 6 WIRE TO THE BUSHINGS SO THAT THE BOX IS BONDED. |
| David Hyatt | What such a large wire? I understand the table but there is a difference between bonding and grounding. Does this Tbl apply to both? I see the table is for grounding raceways but I am not using this from my equipment ground so I am definitely bonding. Am I getting confused on this subject again? Help. The bonding jumper would still have to carry the fault current as far as the pigtail inside the box. Try to explain this to me I seem to be getting confused. |
| Ryan_J | "The bonding jumper would still have to carry the fault current as far as the pigtail inside the box"...Thats right. Thats why table 250.122 applies. |
| Ryan_J | quote: How does that satisfy 250.148? |
| lctrc789 | What I am referring to by bond bushing is the simple act of installing 2 bond bushings at each connector then taking your bond wire (if you ran one) or hit the main ground and make a loop in the wire long enough so that you can use # 6 wire then you have smaller wire to attach a ground screw to the box, by using a crimp on fork or spoon. This allows you more smaller wire and room to make your bonds. I would either use a PVC box and not worry about the bonding or install a 8 x 8 and have plenty of room for the bonding. |
| David Hyatt | Thanks guys. I understand now, lets put a twist in the scenario. What if it was a box say a gutter with many different amperage circuits in it. How would I size the bonding jumper then. Maybe the largest load? |
| electroman | How would installing a bonding bushing on PVC accomplish anything? I would tap off of the equipment grounding conductor with a wire sized per 250.122 and hit the METAL box. If you did this, I think you would satisfy the requirements of article 250. |
| lctrc789 | The bond bushing allows you room to have for a loop in the bond wire ,it is the idea of making room when you have no room./ Just as I have seen ground bars installed in metal boxes and they tap off of them to make room in the box. David as far as mutiple conductors in a SQ. duct read article 250-28 (d). [250][/28(d)] |
| Ryan_J | Pat: 250.28 is for the main bonding jumper, not an equipment bonding jumper. David: See 250.122(C) |
| lctrc789 | David, I apologize for that goof.... Ryan, thanks for that correction, oops... 250-122 yes I don't know what I was thinking. |
| Ryan_J | Pat: I certianly have my share of goofs too. 
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| lucky1122 | David, you said the ground wire was a 2/0 if that were true that would be the size required for a 1000 amp overcurrent device . Equipment grounds are sized according to NEC art 250.122. the required size for a given circuit is based on the overcurrent device of the circuit.now if you were bonding a circuit that large or even smaller it would not matter because the size conductor required as an equipment ground in accordance to Art250.122 would also apply to the equipment bonding jumper as well . now if the 2/0 you are talkin about is the feeder size then the overcurrent device to protect that size wire would be a 175 amp breaker which would require a #8cu equipment ground remember service grounds and bonding jumpers are sized from 250.66 while anything load side if the oc device is 250.122 |