Circuit good, wire outside breaker box no good?

Thread Starter

D zooswanko

Joined Aug 1, 2019
7
Today i noticed my furnace wasnt firing up. Checked all switches and the breaker switch and all were on. Started checking wires and came to find that the wire powering it was not live. Opened the breaker box and the circuit switch and wire connected to it were good. I traced the wire up and just outside the breaker box, the wire had no power in it. How could it be possible that the wire has no power just outside the box but has power at the circuit switch? Have not been able to figure this out.
 

dl324

Joined Mar 30, 2015
8,920
Welcome to AAC!

When you measured the voltage at the breaker, were you measuring on screw that holds the wire or the actual wire?

I traced the wire up and just outside the breaker box, the wire had no power in it.
How are you measuring the voltage on the wire outside of the circuit panel? It should be insulated.
 

Thread Starter

D zooswanko

Joined Aug 1, 2019
7
Welcome to AAC!

When you measured the voltage at the breaker, were you measuring on screw that holds the wire or the actual wire?

How are you measuring the voltage on the wire outside of the circuit panel? It should be insulated.
I tested the actual wire in the box, not just the screw and i tested the wire outside the box with the same tester that works on insulated wires. The pen that lights up and beeps.
 

dl324

Joined Mar 30, 2015
8,920
Did you use the non-contact tester at the breaker? If you did, how do you know it didn't pick up voltage from the screw and not the wire?
 

Thread Starter

D zooswanko

Joined Aug 1, 2019
7
Did you use the non-contact tester at the breaker? If you did, how do you know it didn't pick up voltage from the screw and not the wire?
I assume it is considered non contact but it is pretty accurate on contact of an insulated wire. I tested the wire reasonable distance from the screw.
 

Thread Starter

D zooswanko

Joined Aug 1, 2019
7
1. Is the thermostat calling for the furnace to operate?
2. Did you measure the voltage as it enters the furnace?
All I've done is used the pen to determine there's no power in the wire going to the furnace at all. Theres no power reaching the thermostat. Power stops in the wire right outside the breaker box.
 

LesJones

Joined Jan 8, 2017
2,323
Proximity voltage sensors can give misleading results. Make sure that you touch something earthed while using the sensor. If in doubt use a proper AC voltmeter and test for voltages with respect to mains neutral.

Les.
 

Thread Starter

D zooswanko

Joined Aug 1, 2019
7
Proximity voltage sensors can give misleading results. Make sure that you touch something earthed while using the sensor. If in doubt use a proper AC voltmeter and test for voltages with respect to mains neutral.

Les.
But why would the wire in the box in the wire set it off but not the same wire outside the box? Doesn't make sense
 

narkeleptk

Joined Mar 11, 2019
372
Your issue does not make sense in general. I believe people are wishing to simply RULE OUT it being an error in the testing equipment. Consider using a different tool the same as a second opinion. It might tell you the same thing or it might not, least you will have more information.

It sounded like some posters believed the pen could pick up false reading inside box, which may mean your issue is as simple as a faulty breaker.
 

dl324

Joined Mar 30, 2015
8,920
But why would the wire in the box in the wire set it off but not the same wire outside the box? Doesn't make sense
It doesn't make sense. That's why you should measure the voltages by making physical contact with the wire at the breaker. Not the screw on the breaker and not on the insulation with a non-contact tester.

I suspect either a bad breaker or a loose wire. You can't eliminate things unless you know exactly what you're measuring.
 

Thread Starter

D zooswanko

Joined Aug 1, 2019
7
Your issue does not make sense in general. I believe people are wishing to simply RULE OUT it being an error in the testing equipment. Consider using a different tool the same as a second opinion. It might tell you the same thing or it might not, least you will have more information.

It sounded like some posters believed the pen could pick up false reading inside box, which may mean your issue is as simple as a faulty breaker.
Ill check with a multi meter and post the update
 

JoeJester

Joined Apr 26, 2005
4,077
What is the model number of your furnace?
What is the model number of the thermostat?

Do you have the servicing diagrams?
 
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