Switched grounded conductors

[mjf]

R+R a few luminaires in my 1880's home and find that in each case the gc was switched instead of the ungrounded conductor.
Wondering if there was a time when this wiring methed was common practice and/or acceptable. I was taught to always switch the ugc.

 

[Jim W in Tampa]

Yes at one time they did do this.

 

[LarryFine]

At one time, the hot and grounded conductor (120v service) were both fused, too.

 

[480sparky]

1923 is the first NEC I can find a reference to not switching the neutral.

 

[480sparky]

FWIW, the prohibition on switching neutrals disappeared in the 1928, '30 and '31 NEC. It shows back up in 1933.

 

[benaround]

Knob and tube three ways you switch the hot sometimes and the grounded sometimes.

Feed 120v to the travelers, take the point side of each switch to the light.

 

[mjf]

Thanks for the replies. FWIW the wiring is all BX. As I replaced each fixture I rewired each cieling box and switched the UGC.

 

[augie47]

Thanks for the replies. FWIW the wiring is all BX. As I replaced each fixture I rewired each cieling box and switched the UGC.

you are probably aware, but the "old BX" is a somewhat dangerous critter.
A short can cause the metal "wrap" to become a "heater" due to the resistance. Thats why today's BX (AC) has the bond strip.

 

[benaround]

You got that right, Gus. The first time I saw it, there was about a 30' piece just as red as

a toaster wire, man I came out of that attic and ran to the basement and pulled the main.

Never trusted it after that.

 

[mjf]

you are probably aware, but the "old BX" is a somewhat dangerous critter.
A short can cause the metal "wrap" to become a "heater" due to the resistance. Thats why today's BX (AC) has the bond strip.

Yes, I am aware of that, and since I've been in this house I have slowly but surely been either replacing the wiring and/or lessening the load on existing circuits.

 

[LarryFine]

A short can cause the metal "wrap" to become a "heater" due to the resistance. Thats why today's BX (AC) has the bond strip.

It's actually (in theory, anyway) inductive impedance caused by the spiral wrap, not just DC resistance, which is why the thin bonding strip is effective. It only needs to short each turn to its neighbors.