Bad Neutral?

Hv&Lv

Senior Member
Location
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Occupation
Engineer/Technician
I have a place that I thought was a bad neutral. Had all the signs of a bad neutral when the HO was telling me about it.

The refrigerator motor starting smelling and making weird noises. The microwave was screeching and the smell was there also.

Dishwasher, TV, thermostat, all out in the garage with stinking motors and weird noises...

Trhe control board on the stove.... it was popping and the burning smell was there also.

All this stuff is in the garage now.

I go to the house and check the meterbase with a “super beast”. Nothing..all is good. I go through and tighten everything in the panel anyway. Nothing...

I remove the neutral from the POCO and check it also..



After all this I run a hairdryer in the house at the outlets while checking voltage. I find a circuit that goes from 123.5 to 114 when the hairdryer is turned on. I leave the dryer on and go outside to the panel. The voltage at the AFCI for that room is 123.0. Measured 12.4 amps. A 9 volt drop in a 15 amp circuit with 14/2 wire, about 25 ft of wire max. The outlets are daisy chained as usual.

The other side was 124.2.



Checked the panel with my mini Flir and read a little over 100° on the AFCI breaker that had the dryer on it for about 5-8 minutes.



This hair dryer had tripped an AFCI the week before after running for about 2-3 minutes (according to the HO)



It’s got me a little stumped.

Suggestions?
 

James L

Senior Member
Location
Kansas Cty, Mo, USA
Occupation
Electrician
Did you check the voltage on the other leg while hairdyer was running, or at idle?

Did you check voltage at the main while hairdryer was running?
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Was this the sort of AFCI that has ground fault protection and requires the circuit neutral to pass through the breaker?

I'm thinking some past event looked like a loose neutral in the sense of overvoltage damaging equipment, and the AFCI was damaged.

You still don't know what caused the overvoltage damage.

Jon
 

Hv&Lv

Senior Member
Location
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Occupation
Engineer/Technician
Was this the sort of AFCI that has ground fault protection and requires the circuit neutral to pass through the breaker?

I'm thinking some past event looked like a loose neutral in the sense of overvoltage damaging equipment, and the AFCI was damaged.

You still don't know what caused the overvoltage damage.

Jon
Actually it was the AFCI type you describe
When I put the meter back in the lights came on, like it was starting up, then went off
 

oldsparky52

Senior Member
If it's an OH service, what about a loose neutral connection that opens when the wind blows? (just a WAG)

I think I'd have to check every outlet in that "daisey chain".

One other thing, using Larry's method, take an extension cord and see if the VD at the hair dryer is evenly divided between the neutral and hot, if it's not you definitely have a connection issue between the panel and receptacle. Did you check the VD through the receptacle?
 
Last edited:

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
If it's an OH service, what about a loose neutral connection that opens when the wind blows? (just a WAG)

I think I'd have to check every outlet in that "daisey chain".

One other thing, using Larry's method, take an extension cord and see if the VD at the hair dryer is evenly divided between the neutral and hot, if it's not you definitely have a connection issue between the panel and receptacle. Did you check the VD through the receptacle?
Yes.
Explain Larry’s method?
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Larry has many times suggested using an extension cord from a known good source to use when checking voltages where you are having issues. You test to a known good hot or neutral in the cord to whatever you are trouble shooting.
Got it! I remember now.
Thanks!
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
A 9-V drop on 25' of #14 with a 12.4 amp load does not compute. There must be additional resistance in that circuit.
I agree. They have about 6 outlets on the circuit but there’s nothing plugged in the outlets.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
If while under load with the hair dryer, you checked voltage at each receptacle, maybe that would help determine where to look?
I did. It keeps getting better as I get to the breaker, but nothing extreme. Going to get rid of the backstabbing this weekend in ALL the outlets in the house
 
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