ECN Forum Forums Code Related Discussion NEC & other Code issues Torque

Don, I understand that. George's original post dealt with an inspector and what I assumed was a new installation inspection. In that situation torque wrenches of the type I use could be used to verify torque values without over-torquing the connection. In my area the equipment isn't energized until the inspection has been conducted and passed. I don't think it is wise to re-torque terminations periodically. Torque to specs upon initial installation and then leave them alone.

If you are using a battery drill, keep upping the torque until the screw strips on a old sample screw-then set it for 50% of that stripping value. Question: as the battery gets weak, does the torque, say, at level 4.5, change? For large lugs,I use an automotive-type visual torque wrench-I have had problems with the clicking type. Also,I do not see the problem with re-torqueing. 60 inch/pounds is 60 inch/pounds-all day long. I could be proven wrong, but,I think it would take a huge amount of pressure, say, 150% of the torque value, to damage the conductors. Also I thought "cold flow" was the initial electric current when equipment is energized. A connection that is too loose will arc during cold flow, but stop arcing when the wire is heated up. A normal conection will not arc during cold flow. Is that correct?

George:

NFPA NEC 90-7 says: "It is the intent of this Code that factory installed internal wiring or the construction of equipment need not be inspected at the time of installation of the equipment except to detect alterations or damage, if the equipmkent has been listed by a qualified electrical testing laboratory.

For example Cutler Hammer in the installation instructions state that their connections should be tested for tightness. The reason they give is because in transportation they losten up. They state to test 10% and is they find 1 loose then proceed to test 100%.

I would suggest you advise your contractors to have a torque wrench available for the equipment inspections. What they will neglect the most are bus connections.