What constitutes a good bond

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John Adams

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Lady Lake FL
As a newbie to this forum and a telecomm person, I'd like to get opinions from electrical people. Here's my short list of questions
1. Here's the scenario, many of our electronic equipment is placed in free standing racks or cabinets. They're attached by using an ell bracket that attached to the chassis of the equipment (metal) and the other end goes to the metal rack or cabinet. A very smart EE says that by placing two screws/bolt on both ends that a bond is formed. The bond is accomplished because the bolt/screw is making metal to metal contact as it passes through the chassis and the rack even though both items are painted on each side. To me, that does make sense......................your thoughts?

2. On a bonding busbar using two hole lugs and bolts, should the nuts be on the outside or behind the bar? Personally I suggest on the outside. And the smart EE noted above agrees with me. your thoughts? 80% of the time, the bolt heads are on the outside
 
infinity

infinity

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Journeyman Electrician
1) The bond is only as good as the hardware used to cut through the paint.

2) I like putting the nuts on the ouside when using terminals so that I can torque the nut and not turn the bolt with the torque wrench. IMO that is a more accurate torque value but in reality it doesn't really make much of a difference. We see equipment come with the nuts on the inside all of the time.
 
J

John Adams

Member
Location
Lady Lake FL
What is the recommended (or mandatory) torque value when "re-torqing"

On question one, I guess a mathematical person could figure out how much (or many) of the bolt threads are making metal to metal contact as it passes through the unpainted interior surface. Based on that, it probably could be equated to a particular AWG. In my uneducated guess, I;d say it equates to a 16 to 18AWG.
 
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