fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
I've been presented with the following problem:
20x20 2-stall garage, wooden construction, NM-B wiring. Attic over garage, finished ceiling. Wiring either notched into rafters or run on top of rafters and stapled using uninsulated staples. Attic then floored with OSB which is nailed down with 1 to 1? inch nails. Fiberglass batting with paper vapor barrier attached to fiberglass.
Wall boxes plastic. Junction boxes metal. Connectors wirenuts and buchanon crimps. About 10 duplex receptacles, 2 3-way switches. 2 8ft 2 tube 1 pin flour. fixtures. 2 garage door openers. Receptacles and lights on one circuit. Openers on another.
Homeowner plugged in a battery charger. Lights went out. Breaker tripped and would reset for only a second or so before tripping again.
Another electrician there before me. Checked ballasts, seemed ok. Heard "arcing" in attic. Told the homeowner to move stuff in attic in prep for taking up floor.
------
So I show up reset breaker, trips 2 seconds, helper in garage reports light flicker, no more "arcing" noise. Look up in attic at j-boxes no evidence of arcing found. Look at box the battery charger was plugged into, nothing apparent there. Look at 3-ways nothing apparent there. Take up some flooring, find no evidence of arcing, do find mouse poo and chewed paper but no nibbles on cable where I looked. Found 1 run of NM that had "drawn" the brown goo from the paper over the insulation where it touched.
Pulled neutral for the circuit at the panelboard. Turned on breaker. Breaker held. So not a ground fault to grounding wire.
Assuming it is a hot--neutral fault.
Here's my plan.
1) try another breaker (easy)
2) terminate white/black at panelboard using a 1kOhm resister
3) pull hot to lights
4) check resistance of lights
5) pick a receptacle ? way around wall disconnect, look for 0 or 1Kohms or open. if zero found move one left and right repeat....
This is the first time I've gotten into this and I'll applying how I would trace a shorted fire alarm pair.
Looking for better, practical system.
Thanks
20x20 2-stall garage, wooden construction, NM-B wiring. Attic over garage, finished ceiling. Wiring either notched into rafters or run on top of rafters and stapled using uninsulated staples. Attic then floored with OSB which is nailed down with 1 to 1? inch nails. Fiberglass batting with paper vapor barrier attached to fiberglass.
Wall boxes plastic. Junction boxes metal. Connectors wirenuts and buchanon crimps. About 10 duplex receptacles, 2 3-way switches. 2 8ft 2 tube 1 pin flour. fixtures. 2 garage door openers. Receptacles and lights on one circuit. Openers on another.
Homeowner plugged in a battery charger. Lights went out. Breaker tripped and would reset for only a second or so before tripping again.
Another electrician there before me. Checked ballasts, seemed ok. Heard "arcing" in attic. Told the homeowner to move stuff in attic in prep for taking up floor.
------
So I show up reset breaker, trips 2 seconds, helper in garage reports light flicker, no more "arcing" noise. Look up in attic at j-boxes no evidence of arcing found. Look at box the battery charger was plugged into, nothing apparent there. Look at 3-ways nothing apparent there. Take up some flooring, find no evidence of arcing, do find mouse poo and chewed paper but no nibbles on cable where I looked. Found 1 run of NM that had "drawn" the brown goo from the paper over the insulation where it touched.
Pulled neutral for the circuit at the panelboard. Turned on breaker. Breaker held. So not a ground fault to grounding wire.
Assuming it is a hot--neutral fault.
Here's my plan.
1) try another breaker (easy)
2) terminate white/black at panelboard using a 1kOhm resister
3) pull hot to lights
4) check resistance of lights
5) pick a receptacle ? way around wall disconnect, look for 0 or 1Kohms or open. if zero found move one left and right repeat....
This is the first time I've gotten into this and I'll applying how I would trace a shorted fire alarm pair.
Looking for better, practical system.
Thanks