How to tell if your AC wiring needs an upgrade

BTW, the voltage drop calculators are great. I have no problem with them. The reason I am recommending measuring the neutral is that the calculator doesn’t actually take into account any actual problems inside your house.

If yo know you have 12 gauge wire, and you know it is 45’ long and that your audio system consumes a certain amount of power the voltage drop calculator will give you the best case scenario, but your home may not be best case ... 🤣

Nothing wrong with looking at the calculator and measuring the neutral before you decide what your needs are.

Rude? I wasn’t being rude. But your response certainly is. What is your problem Eric?

Stating "FALSE" by itself is actually pretty rude, it’s also false when you aren’t really reading my statement, you are answering a problem/statement I haven’t made.

Also, my name isn’t Eric, so that’s another problem right there.

I was being honest in my response. Not just for your benefit but for others reading your thread. Too much disinformation is given about the purpose and what the electrical service to earth connection is for...

And that’s why you are not reading my posts accurately. What the purpose of the ground is in terms of the NEC and basic electrical installations is not the same as what we can measure and why we can measure these values. The first is about how a home should be built, but I’m talking about the physics of electricity and what we can infer.

We can measure the voltage on the neutral relative to ground and use it to tell us something without opening up the service panel because one has current and the other does not. That’s not false, that’s physics. It’s also a lot safer than opening up a panel for the average consumer. 

@deludedaudiophile - Things get a little complicated, since the V on the neutral may be the opposite phase of your circuit, but if you assume everything else in the house is off, the Hot to N is usually <= Hot to ground. As your circuit draws more current, the N voltage will rise, the Hot will drop, and the V drop across either will balance.

Try the same with a coffee pot instead! :)

@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).

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.