The Shocking Truth About Neutral Wires
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Why am I getting 120 volts from a neutral wire? Why There May be Voltage on a Neutral Wire. Some of the worst shocks I have ever received while working on live circuits was from neutral wires, here is why and How You Can Prevent Electrical Shock from a Neutral Wire. © By: Dave Rongey |
120 Volts on a Neutral Wire
Electrical Question: Why am I getting 120 volts from a neutral wire?
- Is it normal to have 120 volts from a neutral wire?
This electrical wiring question came from: Dan, a Homeowner from Kailua, Hawaii.
Dave’s Reply:
Thanks for your electrical wiring question Dan.
Wow – This is a Loaded Question, so here goes!
Why There May be Voltage on a Neutral Wire
- 120 Volts on a Neutral Wire
NOTE: Even though this question lacks a lot of information, (such as what are you testing and how you are testing it), however I will explain a few situations where you are sure to get a 120 volt reading on a neutral wire. Lets say you have an incandescent light bulb in a fixture. - Light Bulb Circuit Example
The light bulb itself has a small coil of wire which glows bright when power is applied. One side of this coil of wire connects to a hot wire, the other side connects to the neutral wire. When power is applied it runs through the coil, lights it up, and the power flows to the neutral and back to the bonded ground system of the electrical panel. This completes the circuit. - Disconnected Neutral Wire
Now I disconnect the neutral wire anywhere after the connection to the light bulb, and using a voltage tester connect one lead to the disconnected neutral wire from the light fixture and the other tester lead to the neutral wire that continues to the electrical panel. If the power was turned on to the light bulb the light bulb would not light up, however I will get a 120 volt reading on my tester because the tester has been placed in the middle of the neutral wire which runs back to the electrical panel and my tester is in fact completing the circuit in a very limited way due to the internal circuitry of the type of tester being used. - The Flow of Electricity
The amount of electricity flowing through the tester depends on the type of tester being used. If the tester is a digital type then no current would flow through the tester, but if the tester was an inductive type that has a coil of wire then there will be a flow of electrical current that goes through the tester, yet in each instance the amount of electricity would depend on the resistance of the tested circuitry.
Now for the Shocking Truth about Neutral Wires
- Shocks from a Neutral Wire
If you understand the explanation above then you should realize just how easy it is to get an electrical shock from a neutral wire, in fact some of the worst shocks I have ever received while working on live circuits was from neutral wires. This happens when the circuit is completed either by the connection of the neutral wire path back to the ground system or any other connection that is grounded including a person. - Resistance and the Circuit Path
The shock can be lethal because of the amount of electricity that can flow through the person due to the connected load and their resistance or lack of resistance a person may have to a ground source. The danger takes place if a person gets into the awkward position of being right in the middle of the neutral path to ground, and it hurts like the dickens, can knock you on your rear end, throw you across the room, cause you to yell, or any manner of uncomfortable results including possible lethal results including death! - Turn Off the Circuit
This is why it is extremely important to always positively identify and turn off any electrical circuit that you may be working on, even if you are working on just the the neutral wires, because if you become grounded or caught in the middle, your sure to get shocked, and this is called Not Fun!
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Hi Forrest,
You are absolutely correct – I totally agree!
Thanks for your comment,
Dave
I’ve always found it more useful, particularly in 3-phase 4-wire situations if the “Neutral” was referred to as a grounded conductor. If you consider it as a conductor, just like the “hot” wire, you’ll treat it with more understanding and respect.
Hi Russell,
I’d like to know a little more about the lights you want to install because if they are 120 volts then the power source should be the same as before. As for the original fluorescent light fixtures, make sure the ground wire is authentic and functional and bonded to the metal housing of the light fixture otherwise the lamps may be sluggish to start especially in cold temperatures. I too am experiencing the same thing in my shop where I have older 4 foot fixtures, the old shop light style, and I am having a pill of a time with lamps, they just do not last, and with the new increase in the cost for replacement lamps I am rethinking how I might upgrade, so I too would love more info about the fixtures you are planning to install.
I look forward to your reply,
Dave
The home I bought was built in 1979. There are several flourescent light fixtures in the ceiling and none of them are working very well. Rather than buying lights, and ballasts, plus time involved to get them working correctly, I decided to replace the old fixtures (2 x 8′ lamps) with new T5 High Output Heavy Duty Strip ( 4 lamp T5HO) as I work in the garage a lot. I am 57, so the added light would be a welcome site.
Problem: When I removed one of the old fixtures, I discovered the wiring supplied was 14-2 romex (white/black/ground) and the new fixture is set up for 14-3 (white/black/red/ground). Is it possible to use the existing wiring or must new wiring be run?
Great answer to a question more common than some people think!
We’re often getting similar questions from customers. We’ll point them to your detailed explanation 🙂