It's been a while since I've done this and reading here tells me the codes have changed a bit, so I ask:

I plan to replace the light circuit in a basement. The original wire is 75-year-old BX and there are some 50-year-old changes that never met code. Also, we need more fixtures; temporary lights have been out of code for at least 30 years. I will be using BX on a new 20-amp circuit. There's a fifteen-year-old main breaker panel, GE, 200 amps, plenty of empty spaces.

General advice is welcome, but here are some specific questions: First, I've been told that when connecting to some light fixtures, a special grade of wire (special grade of insulation) is needed. How can I tell what fixtures require this, and what kind of wire will I need?

Second, I'll be replacing the switch loop to the head of the stairs, including the switch. The fixtures will be new, two near the heating/HW plant and two at the opposite corners of the basement. I need to know the proper color/marking of wires in the switch loop when using BX. (Can electrician's tape still serve as a permanent color marking on the insulation?) Also, if the run from the main panel visits the fixtures/boxes in order A-B-C-D and the junction box for C is closest to the switch, if I run the switch loop from box C which (color) conductors do I use for the switched and unswitched hot lines from boxes A-B and B-C? Finally, I plan to use separate junction and fixture boxes at A, B, and C, rather than mounting the fixture on the junction box. Are there strong reasons one way or another?

Fourth, I will be using existing (abandoned) holes in joists (2x12) where I can, and drilling in the center third (vertically) and the center three-fifths (horizontally) where I must. I do not want to drill the main beams, however, and I will have to make at least one and probably two such crossings. What are the current rules about simply dropping below the beam to go across it? I would do this adjacent to the lally column to avoid placing the BX out in the middle where something would be likely to snag on it. (Minimum clearance from the floor to the beam is just under eight feet.)

General lighting loads use 14 AWG cable. The Ampacity of the circuit is 15 Amps.

Normally, you use NM cable. You may or may not be able to use that cable depending on the codes that the AHJ have in your area. NM cable is allowed by the NEC Code.

Don't worry. I'll put in as much new stuff as I can without touching anything existing. Then, with someone else around, I'll cut the main, put the new breaker in, disconnect the existing lamp circuit, and close the panel. (I'm not yet sure that nothing else is on this 75-year-old circuit.) THEN remove the switch, pull replacement wire, etc.

Hmm. Probably should add the first wire segment from the breaker (capped with wirenuts) at the same time as the breaker; it's one less intrusion into the panel.

I'm not doing it this weekend. This is a project, and the final part will be done when my brother is in town.