does this mean we cant replace newer fixtures onto old nmd cable that isnt rated for 90degrees... we have to sleave with 90 degree heat shrink before replacing a light fixture with a newer one. I wonder if home depot salesperson tells the diyer about this
30-408 Wiring of ceiling outlet boxes
(1) Branch circuit conductors having insulation suitable for 90 °C shall be used for wiring of ceiling outlet boxes on which a luminaire is mounted, except for boxes in wet locations where Type NMW or NMWU cables are used. (2) For purposes of compliance with this Rule, the ampacity of 90 °C wire shall be limited to the ampacity of 60 °C wire.
The conductors in ceiling outlet boxes are subjected to an increased operating temperature due to the additional heat from the luminaire mounted on the box. This can cause the conductor's insulation to deteriorate. Rule 30-408 requires that all branch circuit conductors installed in a ceiling outlet box on which a luminaire is, or might be, installed have insulation rated for at least 90 °C. An exception to the 90 °C insulation rating is allowed when the conductors are installed in a box in a wet location and the cables used are types NMW or NMWU. Subrule (2) requires that the maximum ampacity of these conductors not exceed what is allowed for 60 °C insulated conductors. The purpose of this requirement is to reduce the heat from insulated conductors carrying the higher currents allowed for at the higher insulation temperature ratings
here is the ticket for fixtures for refit. Read the labels and instructions with the fixtures but as a guideline any fixture that mounts flush to the ceiling requires 90 degree wire. Fixtures like chandeliers or pendants will not likely transfer enough heat back to the box are probably safe at 60 degrees. Forget the heat shrink, the heat will still transfer beyond the box up the conductor and I have seen at least 1 insulation failure beyond the box. Most of us recall knob and tube rewires of the 80's. Light fixtures only got rewired if they were accessible from the attic. Otherwise they were rewired to the switch. If the fixtures never changed there was not usually a problem if the bulbs were on a pendant and the fixture wire could dissipate the heat. Now we have so many flush to the ceiling fixtures and LV fixtures with the transformers in the box that the old 60 wire in the ceiling boxes has lost its insulation and the guy who changed the fixture used heat shrink or more likely tape to repair the brittle insulation. Fire waiting for opportunity. It is possible to install a 18" section of 90 degree loomex and junction the K&T to provide heat dissipation and protection to the 60 degree wire but where do you put the JB? Not stuffed into the joist space I hope?