Finding an open in a circuit
- Thread starter Raccoon 3
- Start date
- Status
brian john
Senior Member
- Location
- Leesburg, VA
Isolate, test and conquer.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
090816-1958 EST
Suppose you are dealing with a branch circuit with many outlets. Connect to the last outlet a load such as a 1500 W heater. Use a heater with no fan. If that is not feasible then use a 250 W bulb as the load. Then go to each outlet on the branch circuit and measure voltage. If voltage is normal, then check the next outlet.
Between and including the last outlet with good voltage and the next one along the circuit where voltage is bad will be the problem. The fault could be between either outlet or at either one of the two.
Other measurements will determine if it is in the neutral or hot wire.
You may have to use guess work to determine the order of the outlets on the circuit.
If you need I can describe a procedure to use to determine the order of the good sockets on a circuit, and if only hot or neutral is bad a technique for determining the order beyond the problem.
.
Suppose you are dealing with a branch circuit with many outlets. Connect to the last outlet a load such as a 1500 W heater. Use a heater with no fan. If that is not feasible then use a 250 W bulb as the load. Then go to each outlet on the branch circuit and measure voltage. If voltage is normal, then check the next outlet.
Between and including the last outlet with good voltage and the next one along the circuit where voltage is bad will be the problem. The fault could be between either outlet or at either one of the two.
Other measurements will determine if it is in the neutral or hot wire.
You may have to use guess work to determine the order of the outlets on the circuit.
If you need I can describe a procedure to use to determine the order of the good sockets on a circuit, and if only hot or neutral is bad a technique for determining the order beyond the problem.
.
jeremysterling
Senior Member
- Location
- Austin, TX
I used a pasar open circuit tracer to pinpoint the exact location of the open ckt behind sheetrock. I punched my screwdriver through the 'rock and hit the dead center of the covered up device box that had not been pigtailed.
K8MHZ
Senior Member
- Occupation
- Electrician
I have a conductor tracer that works well but must be used on a de-energized circuit. I have located open splices in buried boxes with it. Like most low end test equipment it takes some practice and finesse to get accurate results.
I think mine is marketed by GB. It's called a 'line tracer' or something like that.
I think mine is marketed by GB. It's called a 'line tracer' or something like that.
I believe the Pasar tracers are the AT-2000 series of Amprobe advanced tracers...
- Location
- Massachusetts
Yes, great tool but $800.00 or more.
e57
Senior Member
- Location
- San Francisco, CA
Time Domain Reflectometer - yes - it is an actual item, not just a funny name.
Heres a little about them. I have used several models over the years to find all kinds of wonderfull things. Hidden boxes, shorts, shorts that have blown open, resistive splices, really long sheet rock screws....
Combine this with a radio style circuit tracer to lay out the path of the wiring, then TDR finds the distance to the problem. Most are very accurate depending on the accuracy of the input info, and some (Graphic models) are a little more interpative, but that can help in many situations.
Short of spending a few K's....
Draw up a floor plan with line diagrams of what does not work, and whatever does work near the begining and end of what doesn't... - then ask yourself - "How would I have wired it?" Trust me it works better in your head when you can see it on paper in front of you.
Heres a little about them. I have used several models over the years to find all kinds of wonderfull things. Hidden boxes, shorts, shorts that have blown open, resistive splices, really long sheet rock screws....
Combine this with a radio style circuit tracer to lay out the path of the wiring, then TDR finds the distance to the problem. Most are very accurate depending on the accuracy of the input info, and some (Graphic models) are a little more interpative, but that can help in many situations.
Short of spending a few K's....
Draw up a floor plan with line diagrams of what does not work, and whatever does work near the begining and end of what doesn't... - then ask yourself - "How would I have wired it?" Trust me it works better in your head when you can see it on paper in front of you.
- Status