Although Mike puts heavy emphasis on bonding I have found countless violations of good practice. Electricians should understand the a bond that has a 10 ohm resistance across it can cause heavy damage or death. A solid bond should have less than 1 ohm resistance. In the case of grounds on VSD a 2 ohm bond could cause current flow through the motor bearings thereby destroying them.This is why the code only permits specific screws to be used in bonding. Self piercing sheet metal screws are a no no. Remember aluminum almost always has a resistive oxide coating. Use the proper precautions when bonding to it. Of course copper does too but it less resistive. Bob June 7 2016, 7:42 pm EDT
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