Help needed: bizarre voltage readings


Feeling that my system can sometimes sound a lot worse than usual, I got a voltage meter to check if something was wrong with my AC power. Imagine my surprise when I found that one of the receptacles measured 122V between hot and neutral, 4V between ground and neutral, and 4V between ground and hot. HOW IS THIS EVEN POSSIBLE? If hot and neutral are 122V apart from each other, they simply cannot both be 4V away from ground, right? I tried taking the readings several time and they didn't change.

I tried the meter on several other outlets, including a couple that are on the same circuit as the problem outlet, and they all measured okay: 120-122V between hot and neutral, 120-122V between hot and ground and 0V between neutral and ground. So at least we know the meter is okay.

Please help. I'm really confused.
cpclee
Appreciate the article. But if the ground outlet's ground is not connected to anything, should the reading give 0V instead of 4V between hot and ground and between neutral and ground?

Voltages are everywhere...if the ground is connected to a grounding rod (earth) and not to the neutral at the panel then you are simply measuring the voltage between the floating transformer from your utility and "earth" wherever your "earth ground rod" happens to be buried.

This is not a good thing - if you have a lightning storm and it hits the powerlines then these may carry very high voltages into your components within your home as lightning seeks a path to "earth"...in finding a path of least resistance it may burn something - sometimes even several items can get fried!
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BTW - since a path to ground via a grounding rod may not be very good - this also bypasses the safety protection on your equipment with three prongs - the idea is that the chassis is both grounded and connected to neutral at the panel which means that in the event of an equipment fault you will not encounter high voltages when you touch a chassis and something else that happens to be grounded.
Imagine my surprise when I found that one of the receptacles measured 122V between hot and neutral, 4V between ground and neutral, and 4V between ground and hot. HOW IS THIS EVEN POSSIBLE? If hot and neutral are 122V apart from each other, they simply cannot both be 4V away from ground, right?
Cpclee
You have an open equipment ground.
It could be caused by several things.
* Not made up on the receptacle. Wire may be broken at recept.
*No equipment grounding conductor at the recept rough-in box.
* Open joint at a feed through of another recept rough-in box, or a junction box.

4 Vac reading you are getting? Phantom voltage..... Typical with digital meters.

Connect a load like a 25 watt light bulb in parallel with the meter leads and take a reading....