Locate a Voltage Problem
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How to Locate a Voltage Problem, Electrical Tests for Locating the Cause of Incorrect Voltage. Why is the electrical circuit voltage not reading normal with a voltage tester? © By: Dave Rongey |
Guide to Locating a Voltage or Power Problem
Electrical Question: Why is the electrical circuit voltage not reading normal with a voltage tester?
- I was moving an outlet today to widen a doorway and after doing the work I checked to make sure everything was working good with a cheap multimeter.
- I was a bit shocked when it started registering about 140volts.
- The breaker hadn’t tripped but I shut it off thinking something wasn’t right. I went over everything and it all looked OK and the same as before.
- I turned the breaker back on and it was still reading 140volt.
- I checked other circuits in the house and got the same voltage.
- I started thinking the multimeter was fried, but after trying it at another site and getting the expected steady 115volts there I came back here and it is still reading about 130volts initially and then slowly (about 1volt/second) climbs to about 140volt.
- Am I being paranoid or is this too far out of parameters?
I’ve lived here for about 40 years and never really noticed an issue beyond some AM radio that had interference that I thought was coming from the power lines along the road, and there’s an insulator on one pole that in a heavy fog a while back seemed to be sparking. - I wish I’d put a multimeter in a plug earlier to know if it has always been this way, but I never had a reason to.
- I’m not even sure why I checked the voltage this time, except that it was handy and the circuit I moved had a 14/3 line running a hot carrier down the line and I wanted to be sure nothing was over voltage (220volt) when I was done, if that makes sense.
Thanks in advance for any advice or guidance, and please ask if you need more info.
This electrical wiring question came from Dan, in Canada, Canada.
Dave’s Reply:
Thanks for your electrical wiring question Dan.
How to Check for the Cause of Incorrect Voltage
Application: Evaluating Incorrect Voltage of a Home Electric Circuit.
Skill Level: Advanced – Not Recommended for Homeowners or DIY’ers – Best performed by an Experienced Licensed Electrician.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester and amp meter or load recorder.
Estimated Time: Depends on the type and age of the electric service panel and the access to the circuits to be evaluated.
Caution: Working in an electric panel is dangerous due to arc flash hazards and the possibility of electric shock.
Notice: Making changes to the Home Electrical Service Panel should be done according to local and national electrical codes with a permit and be inspected.
Testing Procedure to Locate a Voltage Problem
IMPORTANT: Voltage Testing inside an electrical panel is not recommended for anyone who is not an experienced electrician. The following is an example of the various testing procedure a qualified electrician may use to help locate a problem with incorrect electric circuit voltage.
- Incorrect Voltage on Electrical Circuits
Call the electric utility provider and have them come out and check the voltage on their side of the electrical service, and be sure to tell them about any associated anomalies. - There are instances when a transformer is failing, or another problem may be occurring on the utility line in the area.
- The Process of Testing the Voltage at the Main Electrical Panel
CAUTION: Do not access the wiring cabinet where the utility company wiring is located within the main electrical panel, or any other section of the electric panel where there are seals or devices to discourage access. These areas are off limits and should only be accessed by an authorized technician of the electric utility company. - Main Power Voltage Test
CAUTION: Main Breakers are still energized on the LINE SIDE of the main supply of the electrical utility power even while the circuit breaker is in the OFF or OPEN position. Turning OFF a circuit breaker disconnects circuit power only to the LOAD SIDE.
At the main panel inside the circuit breaker section, turn off all of the circuit breakers, including the main breaker and test the voltage on the incoming power on the primary side of the main circuit breaker, or test the secondary side of the main breaker with the main breaker on if necessary. - Incorrect Voltage
If the voltage reading is incorrect then call the utility company to recheck the primary circuit and transformer. - Correct Voltage
If the voltage is correct then begin turning on each circuit breaker one at a time and continue measuring the voltage.- This testing process is intended to identify a circuit that is causing a problem with the voltage.
- When the circuit is identified note the circuit number and the equipment or device(s) that are being supplied.
Working With the Problem Electrical Circuit
- Problem with Circuit Equipment
If the problem circuit supplies power to equipment such as an air conditioner then the AC unit will need to be checked by a HVAC service technician. - Problem with a Shared Circuit
If the circuit is a shared with multiple outlets or light fixtures then begin the process of removing or disconnecting all of the devices until the problem has been located. - Circuit Component Problem
If a shared circuit is the problem even when all of the devices have been disconnected, then portions of the the circuit cable wiring will need to be identified, disconnected and tested, one section at a time until the problem is located and repaired.
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