Knob And Tube Circuit

[aaatraker]

Knob and Tube circuit question.
Outlets in bedroom not working, fluke meter reads 61 volts, second meter reads 57 volts both digital. Ideal solenoid meter does not read, 110 volt test light does not light, 24 volt test light does not light. Fluke and ideal inductive test sticks do light up and buzz. All meters and lights checked out good on 120 circuit before testing.

I think that the grounded wire is open in the wall or ceilings I checked some J- boxes but could not find the problem. The grounded wire is tight at the outlets and the panel. I suggested running a new circuit and grounded outlets.

What do you think?

 

[George Stolz]

Re: Knob And Tube Circuit

Scratch that.

What prompted the call? What changed prior to your arrival (or the problem)?

What is the voltage at the panel?

[ January 23, 2006, 12:07 AM: Message edited by: georgestolz ]

 

[LarryFine]

Re: Knob And Tube Circuit

AAA, plug a 3-prong extension cord into a known-good receptacle (not GFCI), and take the female end to the bad outlets. Use the solenoid tester in the cord's hot slot to test for the outlet's neutral, and the cord's neutral slot to test for the outlet's hot.

 

[aaatraker]

Re: Knob And Tube Circuit

Panel voltage 120.
This is a 100 yr old house all the circuits but this one have been changed to romex. The circuit runs in basement, first floor and second floor. They are not sure when the outlets stopped working, I checked where new work had been done, but no lose wires that I could find. Insulation not in best shape, some of wire has been taped over where its coming off, thats why I think new circuit would be safer. Not adding load to this circuit would be better I think.

Ext. cord great idea, I was thinking a single wire to a ground this morning.

 

[al hildenbrand]

Re: Knob And Tube Circuit

Larry's suggestion is excellent.

As an alternative to a solenoid, you might use a cheap D'Arsonval meter movement Volt-Ohm Meter (needle that swings across a bunch of different scales). These are available for $10 - $20 (top) at Radio Shack, home centers, etc. I keep a couple.

Whatever the meter, it must have a low input impedance so it is not fooled by induced voltages. Single conductor K&T is real good at holding stray voltages that will fool noncontact voltage detectors and high input impedance probes (most digital probes).

Running the good grounded extension cord from a good grounded receptacle (the laundry? or maybe the newer 20A small appliance receptacle in the kitchen) takes a little extra effort, but it is excellent for a reference ground, neutral and hot to run diagnostics off of.