Voltage reading with a open neutral??

Addison

Member
Location
Westport
Occupation
Electrician
So I am connecting power to 2 commercial business signs. Very simple set just 120v to a single pole switch as a disconnect for the sign (all supplied and pre wired by tbe sign company).

To make a long story short the signs arent working. I have 120v off the load side of the switch (which is obviously going to the signs) to both my neutral and my ground.

Called the owner of the sign company and he insist the sign was tested several times before being hung.

My only thoughts are a lost neutral. But if i had a lost neutral would i still read 120v from hot to neutral?? Or would the voltage change because of the lost neutral.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
If you are measuring 120V with a normal 'high impedance' meter, then you need to go back and measure with a low impedance meter or with a load connected.

A _poor_ connection either on the hot or neutral side can pass enough current to give a full voltage reading with no load connected, but this voltage crashes when a load is connected.

Jon
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
If the neutral is open at both ends, and is of some sufficient length, there may be enough capacitance for a high impedanace digital meter to show 120 volts.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
If you are measuring 120V with a normal 'high impedance' meter, then you need to go back and measure with a low impedance meter or with a load connected.
Or a solenoid tester, or even a light bulb in a socket with wires.

Or cheat and use the EGC temporarily! as a test of the neutral.

Or an extension cord as temporary power, or even just the neutral.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
If I lost a neutral on a 120v circuit, would I still be able to read 120v between my hot and my neutral??
It depends on what type of tester you're using. A standard voltmeter is good for when you need to know the exact voltage, but a solenoid tester, for example, requires "real power" to indicate voltage.

Or, read the voltage while you have a load connected, anything from a (non-LED) night-light to an electric heater. A voltmeter can show voltage or ground on a floating wire run alongside other wires.
 
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