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Grounding vs Bonding Online Training
 

 
Grounding vs Bonding: 250.92 Service Bonding Continued

April 7, 2006  

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PART V. BONDING   Hi Res - Cable/DSL [9223Kb]


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250.92 Service Bonding Continued

(2) Threaded Fittings or Entries. Raceways containing service conductors are considered bonded to an effective ground-fault current path by threaded couplings or threaded entries on enclosures where made up wrenchtight. Figure 250–129

(3) Threadless Fitting. Raceways containing service conductors are considered bonded to an effective ground-fault current path by threadless raceway couplings and connectors where made up tight. Figure 250–130

(4) Bonding Fitting. When a metal service raceway terminates to an enclosure with a ringed knockout, a listed bonding device, such as a bonding wedge or bushing, must bond one end of the service raceway with a bonding jumper sized in accordance with Table 250.66 [250.92(B)(4) and 250.102(C)]. Figure 250–131

Author’s Comments:
• When a metal raceway containing service conductors terminates to an enclosure without a ringed knockout, a bonding-type locknut can be used instead of a bonding wedge or bushing. Figure 250–132
• A bonding-type locknut differs from a standard-type locknut in that it has a bonding screw with a sharp point that drives into the metal enclosure to ensure a solid termination.
• Bonding one end of a service raceway in accordance with 250.92(B) provides the low-impedance fault-current path to the utility electrical supply source. Figure 250–133



Figure 250–129
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Figure 250–130
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Figure 250–131
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Figure 250–132
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Figure 250–133
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Copyright © 2006 Mike Holt Enterprises,Inc.
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Comments
  • For the longest time, I could not understand why I could not find a code rule requiring bonding on both sides of that nipple between the meter enclosure and the disconnect enclosure. Looking at figuires 250-131 and 132, I still could not see why only one side needed it. After I look at these two figuires for a while trying to imagine the fault current path, I finally saw it in my minds eye. But it took me awhile to see it and I'll bet many electricians are struggling with the same question. If I had only scrolled down a little further to figuire 250-133, I would not have had to strain my pea pickin brain so much. So, what I'm trying to say is that your work with your top notch illustrator is really in tune, with most electricians and you and your team continues to put out the best illustrations I have ever seen. The SOARS book is a good book but their illustrations cannot hold a candle to yours and I think your text is a little better also. I have had many, many teachers over the years and your team is near the top in my book and on the very top by far where electrical training is concerned. That last illustration 250-133 put a big smile on my face and I'll bet on many others faces. THANKS AGAIN FOR YOUR HELP, Ralph Greene

    Ralph Greene
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