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My house is from 1937 they have updated the fuse box with circuitbreakers but the wiring is still old.

I was wondering how to wire new wire to old wiring for an outlet. There are the main lead has 3 wires black, white, and kinda white red looking wire. The casing or the wire is metal.

What kinda of new wiring do i need. What is the third wire kinda white wire for?
 

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The kinda' red wire may have been there so a switch can control one half of the outlet (receptacle) unit.

It is r4ecommended to run a new cable for the new receptacles, etc. all the way back to the panel. While the metal sheath around the existing cables can be a grounding conductor, it may or may not be sufficient and some additional examination and tests would be needed to determinine if it is.
 

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I recommend not using old armored cable wiring that is in place and seem solid and well protected. There could be issues and shorts. My 2-prong circuit tester, the reliable one with some neon gas, will not light up on low voltages. I thought the circuit was off when my metal tools shorted the white/red wiring with crumbling insulation. POW! Sparks flew. It did not trip the breaker. Tested the voltage got a reading of ~6 volts.

Found the breaker at the panel so now I can replace that stretch.
 

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Older wiring without a ground should not be extended. You would be better off running a new cable from the panel.
 

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Yes, Code forbids extending old wiring without a ground wire. 250.130(C) says that if you extend a non-grounded circuit you must retrofit ground at least to the extension. Although those rules can be used to retrofit ground anywhere you want. Sometimes metal jacketed conduit or cable is already a valid grounding path, and carries ground to receptacles and switches via mounting devices. All my work will seem ungrounded. It's grounded.

Degraded wiring cannot continue in service, 110.3(A) and 110.12(B).

Distrusted wiring can be mitigated with AFCI breakers, or better, AFCI+GFCI. GFCI also improves safety on ungrounded outlets and allows 3-prong outlets there if labeled.
 
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