How to tell if your AC wiring needs an upgrade

What is the N-E voltage? What should it read?

ozzy

Hey @ozzy

Ideally, zero, assuming perfect superconductors on the neutral wire, but the reality is that when current flows this voltage rises a little. The neutral and ground are bonded at 1 place (either the meter or your service (the first) panel. At that magic point there is no voltage difference at all. However under normal household operation current flows on the neutral wire, but not the ground wire, and this current flow is what leads to the voltage difference (N-E). Current in the neutral is normal function, but you want to make sure your neutral is big enough, and well enough bonded to ground that this doesn’t rise significantly under maximum load. When it does rise under load, that is about half of the voltage drop seen by any other device on the circuit.  The reasons is that the voltage drop on the neutral is going to be about the same as the voltage drop on the hot wire.  That is, the resistance of your AC circuit is the combined resistance of the hot and neutral, so if we assume that is roughly the same, we can use the neutral drop to estimate the hot drop.  Of course, a bad upstream connection can upset this calculus.

When your outside AC units and hot water heater and stove going there is very little neutral current though since they are 220V and only have hot to hot current (mostly). However any big 120 VAC appliances like window AC units, hair dryers, microwaves, as well as those big class-A tube amps you have heating up the house will.

False...

The ground rod outside has nothing to do with it.

I false your false and raise you a "rude" to go with it.  You missed my point.

erik_squires,

Thank you for that fine explanation. I was just curious because the ad of this device showed that N-E reading as 02. Should that read 02 or 2?

So, then I am wondering what steps are needed to get it back to zero? I have 3 dedicated lines each with 10 gauge wiring, I re-read the ad and I am still a bit confused.

BTW, I ordered one to try out. I will try it first as per instructions to establish a baseline, but I would also like to try it into my Audioquest Niagara 7000.

ozzy

@Ozzy This isn’t a lab grade device and may over estimate by 1-2 volts, but it is relatively accurate. A well wired home can have a couple of volts on the neutral and all is pretty much normal. It happens because you wire homes for safety and cost effectiveness and 2V is just fine.

You want to make sure your home isn’t much higher than that though, AND if you want to know if your audio system is causing your AC to sag (drop in voltage) this is a good way to measure it.

It is rare, but dangerous, that a home’s neutral becomes corroded or fails, in which case that N-E voltage will suddenly rise, and that’s why it’s a good thing to have an eye on now and then. Also, the testing I suggest helps you measure where the problem is. Putting in a new branch circuit is not going to help you if you already have an elevated neutral. Fix that first!

It may help to understand things this way:  The higher the neutral voltage the lower your outlet voltage (assuming you don't have something else wildly wrong).