Birddawg
Member
- Location
- Ann Arbor, MI
- Occupation
- Electrical Engineer
I was called out to a family members old house to identify and fix a short circuit. The house was built in the 1920s and the original nob and tube wiring was still in use. Years ago the electrical service was upgraded and then it was upgraded again. So there was nob and tube wiring, old romex without a ground wire and modern romex such as 14-2 with ground and 14-3 with ground. There was a dead short on the original lighting circuit. This circuit left the circuit breaker panel in the basement in old romex which traveled above a hard ceiling in the basement so we could not tell where it went. The circuit feeds all of the ceiling lights on the main floor, lights and receptacles in two bedrooms upstairs and the light at the head of the stairs. All of the lights were controlled by single-pole switches except the light at the head of the stairs. That light had two three-way switches.
My brother-in-law George and myself went to work. We took every switch out of their boxes and every light fixture down looking for the short. We disconnected each lighting fixture to eliminate the possibility that the short might be in one of the fixtures. It was clear that the original light fixtures were not mounted from boxes and that boxes were added later. Every ceiling box had just two wires coming in so the original connections on the nob-and-tube wiring were made on the wiring itself, not in boxes. I have seen this before in old houses that I have helped remodel. It was standard that the connections were soldered and then wrapped with rubber tape and then friction tape. They didn’t have plastic tape in those days.
All of the switches were in single-gang boxes except for two. There was a two-gang box for the kitchen light that had two switches. The wiring for the kitchen light was original and had two original wires coming into the box which connected to the switch. The other switch had modern wiring for the porch light which worked. It was on a different circuit. There was a three-gang box in the dining room next to the front door with all original wiring coming into the box. One hot wire that had some THHN connected to it and this fed all three switches. Then there was one wire for the dining room light, one for the covered front porch light and one for the outer porch light. None of the switch boxes were grounded nor were there any neutral wires in any of the boxes as far as we could tell. All wires were black. It was clear that the wire connections were made behind the plaster walls.
I had taken the hot wire off of the circuit breaker in the basement and connected it to a lamp socket and then connected a wire from the circuit breaker to the other terminal on the socket. After I screwed in a regular incandescent lamp into the socket and switched the circuit breaker on, the lamp came on full brightness which indicated a dead short. I turned the circuit breaker off and disconnected the white wire from the old romex from the neutral bar and turned the circuit breaker back on. The lamp did not come on which indicated that the hot wire for this branch circuit was shorted to the white wire of the same circuit. Then I reversed the process and with the white neutral wire reconnected, the lamp came on with the circuit breaker on. We left the power on and had another person watch the lamp waiting to see the lamp to go off. George and I inspected all of the boxes on the circuit. The lamp never went off. Please do not point out to me that by some definitions, a two wire branch circuit does not have a neutral. I am using white and neutral to refer to the circuit wire that was connected to the neutral bar.
Please do not criticize me for breaking safety rules. I could write a list of the rules that I broke. I recommend that these procedures not be followed.
I found the short. I want to ask for recommendations for the next step for the sake of discussion. What would be your recommendations?
My brother-in-law George and myself went to work. We took every switch out of their boxes and every light fixture down looking for the short. We disconnected each lighting fixture to eliminate the possibility that the short might be in one of the fixtures. It was clear that the original light fixtures were not mounted from boxes and that boxes were added later. Every ceiling box had just two wires coming in so the original connections on the nob-and-tube wiring were made on the wiring itself, not in boxes. I have seen this before in old houses that I have helped remodel. It was standard that the connections were soldered and then wrapped with rubber tape and then friction tape. They didn’t have plastic tape in those days.
All of the switches were in single-gang boxes except for two. There was a two-gang box for the kitchen light that had two switches. The wiring for the kitchen light was original and had two original wires coming into the box which connected to the switch. The other switch had modern wiring for the porch light which worked. It was on a different circuit. There was a three-gang box in the dining room next to the front door with all original wiring coming into the box. One hot wire that had some THHN connected to it and this fed all three switches. Then there was one wire for the dining room light, one for the covered front porch light and one for the outer porch light. None of the switch boxes were grounded nor were there any neutral wires in any of the boxes as far as we could tell. All wires were black. It was clear that the wire connections were made behind the plaster walls.
I had taken the hot wire off of the circuit breaker in the basement and connected it to a lamp socket and then connected a wire from the circuit breaker to the other terminal on the socket. After I screwed in a regular incandescent lamp into the socket and switched the circuit breaker on, the lamp came on full brightness which indicated a dead short. I turned the circuit breaker off and disconnected the white wire from the old romex from the neutral bar and turned the circuit breaker back on. The lamp did not come on which indicated that the hot wire for this branch circuit was shorted to the white wire of the same circuit. Then I reversed the process and with the white neutral wire reconnected, the lamp came on with the circuit breaker on. We left the power on and had another person watch the lamp waiting to see the lamp to go off. George and I inspected all of the boxes on the circuit. The lamp never went off. Please do not point out to me that by some definitions, a two wire branch circuit does not have a neutral. I am using white and neutral to refer to the circuit wire that was connected to the neutral bar.
Please do not criticize me for breaking safety rules. I could write a list of the rules that I broke. I recommend that these procedures not be followed.
I found the short. I want to ask for recommendations for the next step for the sake of discussion. What would be your recommendations?
