Hello all, there are multiple rooms on the first and second floors of this circuit. After tracing, it is lights and plugs only. I was able to trace and isolate one hot and neutral going from the basement up into a first-floor wall. I was able to reconnect with the other knob and tubes that were attached previously and got those plugs working. But there are still some plugs and lights on the first floor that are off, and all the lights and plugs on the second floor are off. I found a cubby access area on the second floor but saw no boxes or splices in that area. The Hot and neutral that I Isolated shows a short circuit with my Greenlee ckt tracer and continuity between the hot and neutral with my meter. This house was built in the early 1900,s and the receptacle boxes are too small to have any splices in them, I can only surmise that the issue may be in one of the light fixtures. No old fuse panel exists that I can find. All of the ceiling fixtures are ceiling fans with lights, so I turned off switches to the ceiling fans, on the ones that had switches, to isolate the problem, thinking there could be a short through the motor if the pull chain was in the on position. I am letting the customer know that we may have to take off each fixture until we find a splice where the feed comes in a ceiling outlet box. Any help is appreciated.
Hot to neutral short on knob and tube circuit
- Thread starter tld38
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romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
K&T is always an all inclusive octopus , always lousy with tag-on BX over decades of reno's .
I've found many original installs to have been point of use pull chains, w/BX switch loops added afterwards
If your particular situation is so, looking for those add-ons as you TS fixture locations would be my best guess as well
~RJ~
I've found many original installs to have been point of use pull chains, w/BX switch loops added afterwards
If your particular situation is so, looking for those add-ons as you TS fixture locations would be my best guess as well
~RJ~
Ravenvalor
Senior Member
- Location
- Piedmont region of NC
If you applied 120-volts would it trip the breaker? What about under a load? If you can put the circuit under a load could you perhaps pick up some sort of heat signature with a high quality stud finder like the Bosch D-TECT150?
When I applied 120 volts to the common hot wire I isolated, it would immediately trip the breaker. The other common hots and neutrals are working. So, I was able to isolate the one hot and neutral K&T going in the wall. I just cannot find where the two wires are going.
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
I've used a fox and hound to trace in walls. Have found those octopus connections by using one. Just takes some time. Found junction box buried and even no box splice in walls and ceilings.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Wire a high-wattage incandescent bulb in series with the breaker and the circuit wire. That will act as a current-limiter to allow the breaker to stay on while troubleshooting, and will act as an instantaneous current indicator.
Have a helper watch the light and immediately report any flicker or change in brightness. If you're working alone, you can wire in a receptacle instead, and use an extension cord and a lamp to have the indicator light near you.
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
How about disconnect both conductors at the panel and check continuity to the grounded conductor bus?
If there is no ground faults in the branch circuit you shouldn't read any continuity.
Should someone have bootlegged an EGC from the neutral at some time and then polarity ended up being reversed sometime, that makes the frame of equipment energized and if there is some other ground path .... you will have short circuit level current. Remember polarity wasn't necessarily important on most K&T wiring, some cases maybe wasn't a grounded conductor when originally installed either.
If there is no ground faults in the branch circuit you shouldn't read any continuity.
Should someone have bootlegged an EGC from the neutral at some time and then polarity ended up being reversed sometime, that makes the frame of equipment energized and if there is some other ground path .... you will have short circuit level current. Remember polarity wasn't necessarily important on most K&T wiring, some cases maybe wasn't a grounded conductor when originally installed either.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Good point. There may be a fault to ground instead of between conductors.
Ok. lesson learned for me here. the fact that the neutrals and hots are well separated in K&T wiring, I found it hard to believe that there would be a direct short to neutral since there is no equipment ground in K&T. So I realized that the power to the garage went from the 2nd floor to the garage via open wiring in air, like many of the older houses with garages. So, after looking at the overhead to the garage, I saw that the neutral was frozen to one of the legs, and of course, there were bare spots that caused the direct short. bottom line, I solved the issue temporarily with a heat gun. The garage needs to be fed underground in the future. I was very relieved, and my friend was happy. The bottom line is I should have taken more time to assess the situation before tracing stuff inside.
Thanks to all!
Thanks to all!
Ravenvalor
Senior Member
- Location
- Piedmont region of NC
pardon my ignorance. What do you mean by instantaneous current indicator?
ramsy
NoFixNoPay Electric
- Location
- LA basin, CA
- Occupation
- Service Electrician 2020 NEC
Should have diagnosed only, got paid, then recommended new service drop with complete service upgrade.
As is stands now, next time these old wires fly around the fault may burn down the building.
If you can't stand panel flippers attaching new 200A mains to existing 30-Amp service conductors, you must get your license & do it yourself.
It's an exercise in futility to help owner's hire qualified persons in the wild, much less get it inspected.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The brightness will change as you jostle the unintended short. Full brightness = dead short. Partial brightness = resistance in the line. Flickering light = you're getting close as you wiggle stuff.
I once had a similar issue in a house with a mix of K&T, RGS, BX and NM. There was an intermittent short on one of the original circuits, fed from a newer panel through RGS on the basement ceiling.
So I wired in a rubber socket and a bulb, which constantly flickered. It varied from full brightness to almost off, but never a steady brightness. I figured there must be an arcing fault somewhere.
I separated the branches in the first J-box, until I isolated the offending branch. It was an NM cable running up through the basement ceiling to a receptacle in a Wiremold box behind the front door.
I got on the floor and looked at the receptacle. Inside the receptacle, through the slots, I could see a glowing red light, like embers in a fire. It also reeked of cat urine. They cleaned, I replaced done.
My parents garage had wiring like that. 4 wires: L, N and two switch travelers. On windy days, the travelers would tangle and the garage lights would light dimly. I think L & N we’re on the outside of the 4, they never met.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
It wasn't the service wires, it was an overhead feed to the garage from the house. OP said the breaker would trip.
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