When dealing with old 60 degree rated wiring, is it considered an acceptable fix to heat-shrink it for use with fixtures requiring 90 degree wiring?
I can get heat shrink with a minimum activation temperature of 125 degrees C. and a 600V insulation rating. It seems to me that this would be sufficient for protecting conductors in a 90 degree enviroment.
I can give you an opinion John. What you are thinking about should be more than sufficient. But a lawyer in a courtroom would be able to shred it apart. So you won't be likely to find an approval from an AHJ for the method.
I've used heat shrink but someone brought up a very important point on one of the other fprums a while back. Most of us focus on the fact that the ambient heat from the fixure is what we're trying to deal with but forget that the copper is not only a good conductor of electricity but also heat. As such one should not ignore the fact that heat is being conducted by the copper potentially beyond the box itself. So what about the insulation just outside the box? I realize that this may or maynot be a problem and some might consider it to be spitting hares but can it be confirmed that the insulation temperature wouldn't be exceeded outside the box itself? And, yes, I do carry heat shrink tubing in my took box with a heat gun. But are we making an informed decission when we repair or reinsulate the wires? This is something that I never thought of at first.
Much of the heat a conductor at a lighting outlet is exposed to is the heat the travels from the filament along the filament legs through the socket and into the field wiring.
Those of you that service HID fixtures will be familiar with the fact that the porcelain sockets are often fasted to a large piece of aluminum which works as a heat sink to draw much of the heat off the socket and into the fixtures enclosure.
Bob Badger Construction & Maintenance Electrician Massachusetts
Heat Shrink is a cool idea but, by the time the coating on the wire is cooked, the copper is usually weakend to an unusable state and needs to be replaced. I would not reccomend this. If the wire cannot be trimed back to a point where you get good copper & coating....forget it. Replace it!