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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.

Thanks!

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    diy.stackexchange.com/questions/148582/… Could be cloth wires in bx cable, which grounds through the exterior of the cable.
    – gbronner
    Oct 11 '21 at 19:33
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    If you're renting the unit, you shouldn't be doing any electrical work in it.
    – JACK
    Oct 11 '21 at 19:42
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    A picture of your wiring would help. K&T wiring would not have had a ground, but it could have been added later (in either proper or improper ways). There are other old cloth-covered wire types, like early NM cable, that may have a ground included.
    – blarg
    Oct 11 '21 at 19:48
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    You know you have knob and tube if you see loose conductors running inside walls, and you see, of course, the ceramic knobs and tubes used to guide them around. Seeing cloth insulation does not mean you have it. I'd be surprised if a 90s upgrade with a new panel was attached to knob and tube wiring. I would not be surprised if it was attached to slightly older armored cable that included cloth insulation, with grounding provided some other way. Armored cable can also provide grounding in a way that's good enough for a continuity tester but not actually good enough for its purpose.
    – jay613
    Oct 11 '21 at 19:53
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    What actually is your issue? You are worried about consuming "a bit of electricity". If you can specify the power requirements of your kit, and the circuit capacity of the circuits serving your apartment, you could ask a useful question about whether it will work. You can't rewire the building so I don't see the point of worrying about how it's wired. Unless you're the landlord.
    – jay613
    Oct 11 '21 at 19:56
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Thus far, I've replaced the first receptacle in most of the series of receptacles with an AFCI/GFCI because I'm so confused.

Don't do electrical work in a building owned by someone else.

To do that you need 2 things:

  • The landlord's permission to do that, for obvious reasons. AND
  • City approval of you doing the job, which normally requires a master electrician's license, or be a trade-school graduated, bona-fide apprentice working under the supervision of same.

It is illegal in both directions: First in rental units, all wiring must be done by a licensed master electrician. That's to prevent slumlord/amateur work from killing people. Second, amateurs are not allowed to do electrical work on a building owned by someone else.

So amateurs can only work on houses they own and live in. In certain cities, even this is not allowed. Whether Chicago is one of them has been a matter of litigation.

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.

in Chicago

Meaning it will all be metal conduit. And conduit will carry the grounding.

Chicago is oddly paranoid about fires... blame Mrs. O'Leary's cow.

So you looked in there and didn't see any ground WIRES... yeah, there's more to that picture, and your struggle here is due to an essential skill gap.

My laser printer seems to dim the lights in the whole apartment, which is a bit troubling.

Well, laser printers draw a considerable amount when the fuser assembly is on. And the fuser is typically a "halogen bulb" not a resistive heater, so it has considerable inrush current well above the nameplate amp rating for the laser printer. (but within the capacity of electrical wiring given its ability to tolerate SHORT term overloads).

Still, that could be something else entirely: a "Lost Neutral". If you see one phase of power increase voltage when a laser printer (or microwave) on another phase cycles on, that could be a broken neutral wire from the utility's service drop. Happens all the time since the neutral service drop wire is also the physical carrier for the other wires. Whips in the wind for 30 years and snap

However I was able to detect and resolve a lost neutral in my rental cottage, simply by measuring the outlets I had access to, and calling up the landlord's electrician (who lives across the street) to open the main panel and check the meter-side buses... and then calling the PoCo was delegated to me. Fixed in an hour. If

I have some electrical devices that I know use a bit of electricity and want to make sure that I am safe and responsible.

Well, then, take the time to map out which outlet in the unit is on which circuit, which you can do without taking anything apart.

Know the ampacity of that circuit.

Know exactly the amperes each load draws.

And don't overload the circuit.

You certainly do have the facilities and skill to do all that. I can't say that about most people.

Note that a conduit can support up to 4 circuits generally. So if you need more circuits for some reason, it would not be costly for an electrician to fish in wires for additional circuits. Existing receptacles could be split and fed from AFCI or GFCI breakers. For that matter, replacing the cloth wires with modern THHN wouldn't be prohibitive.

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  • Read what you suggested prior to the work. I did consult the landlord. I wouldn't necessarily say I leapt to a conclusion, I more recognized that the wiring was not recently replaced and therefore could be K&T. Having consulted the landlord, I was concerned I might be missing something. I believe the fuser/corona in this model is a resistive heater, but I could be mistaken. I honestly don't know what it draws. I'll figure that out. I've had it in four apartments and never had it do this. Regarding the map, yes I did that, too. Thanks. Oct 11 '21 at 21:12

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