I have recently moved into a 1920s apartment in Chicago. My landlord has only owned the building for a few years and does not know the details of the electrical system. I have some electrical devices that I know use a bit of electricity and want to make sure that I am safe and responsible. I'm also concerned about damaging knob and tube while hanging things.
The panel in the basement is from the early 90s, populated with breakers (non AFCI) and is attached to each leg of the apartment with conduit. At some point in the 80s, a furnace was added in the unit.
In the walls of the apartment though, I notice that most wiring is cloth insulated. I'm assuming it's knob and tube, but I'm also noticing that most outlets are grounded, the ground tests properly, and I have not found any bootleg straps on any receptacles. Also, testing the resistance between grounded receptacles, I'm finding a near-zero resistance - in short, it appears to truly be grounded. Which is very confusing as it appears to be knob and tube.
Thus far, I've replaced the first receptacle in most of the series of receptacles with an AFCI/GFCI because I'm so confused.
If I'm finding low resistance grounds, does it mean that it's likely been replaced with conduit?
Is there a way to bootleg a ground without doing it at the receptacle? I have yet to see a wire on any receptacle or box for the ground. The receptacles are grounded to the boxes via their mounting screws, and that appears to be a true ground.
Is there anything I should be doing other than adding AFCI receptacles where I can?
When the panel was replaced in the 90s with a modern panel, would code have required that all wiring was in conduit?
Was there ever a time cloth insulated wire was run inside conduit?
Finally, does K&T generally follow studs as conduit does, or is it often installed more in the center of walls?
Lots of questions, but I'd appreciate any advice or guidance. I have a few devices that draw 5-10A and don't want to cause any problems. My laser printer seems to dim the lights in the whole apartment, which is a bit troubling.