How to tell if your AC wiring needs an upgrade

Just posted a new blog article on how to analyze your AC wiring using a very inexpensive meter.  Who knows, if you find a problem with your wiring it may just save your home!





Thanks, I just bought one of these.  I recently spent quite a bit of time troublshooting input transformer hum on a tube amp.  The OEM insisted that it was almost certainly DC offset.  It took quite a while to convince myself I had no DC offset and eventually found a blow fuse in the amp taking out one half of the rectifier.   Obviously that fixed the problem. --Jerry

A few years ago, I got a good deal on "as new" Klipsch La Scalla II speakers. I was so excited, I purchased a demo Primaluna prologue premium integrated amp. Couldn't wait to hear them! Wouldn't you know, there was a buzz I could hear 12 feet away at my listening position. Sent the amp to Upscale Audio (not the seller) who gave the amp a clean bill of health. The speakers worked fine with other amps so the problem must have been with my A/C. Drat! Anyone know the cost of a whole-house rewire?

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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.



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.


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 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).

Thinking about this some more, I'd say the most common error you'll find is an outlet with the hot and neutral reversed.  In that case the n-e will show 118 V or so.  Easy to fix.

The higher the neutral voltage the lower your outlet voltage (assuming you don't have something else wildly wrong).


Can you explain this above?

I did the test with a multimeter on kitchen outlets with nothing connected. I measured 0.9V. I plugged in a 25W incandescent lamp and the voltage dropped to 0.4. Was the 0.9 noise?

@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! :)

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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. 

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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.

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The final 0.4V reading could be nothing more an induced voltage by the HOT 120V ungrounded conductor.


I suspect the 0.9V was not correct and was influenced by noise pickup. The 0.4 is likely the accurate measure.


@erik_squires understood your meaning now.  You are using the ground-neutral voltage as a crude ammeter.

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Just plugged in the unit referenced (Receptacle Tester) in this thread. Everywhere I try it it reads 117V (L-N) and 0-.01 (N-E). Screen is green.

Now the really weird thing though is when I plug it into my Niagara 7000 it reads 122V (L-N) and 0 (N-E) but all 3 lights are on and red  which according to the instructions (indicating HOT/GRD REVERSE, OPEN GRD) and the screen turns orangish-red.



Is the AC voltage output of the Niagara 7000 Balanced power? 60V - 0V - 60V? If yes that would create problems for the "(Receptacle Tester)". It’s not designed to be connected to a balanced power system. L to N Voltage it will measure...


I tuned in Audiogon Forum because I have had good experiences on other forums (not audio related) and because I felt ‘comfortable’ with the general tenor of the contributions. I was also quite impressed that some dealers, and even more, some manufacturers (most notably, Atmasphere), would deign to post on technical issues without making even a veiled sales pitch. In a word, I was impressed by the sincerity of many of the posters, including several of those who have reportedly been banned, especially oldhvymec (if I’ve spelled his handle correctly) and the aforementioned hemhtz (again, I don’t know if I’ve spelled his name correctly. Personally, and in my experience, a Forum needs its ‘steadies’ the people you can count on for an opinion one way or the other; they function as signposts, as it were, weathervanes, to tell you which way the wind is blowing, or the tide is turning. They can get tiresome at times, because the other regulars have heard it all so many times before. But there is still comfort in that, for me. I can understand, and have some sympathy, for any new moderator who might feel constrained (or threatened), but ideally, the Forum’s ‘public square,’ free speech’ nature levels the playing field. Because I haven’t been a witness to the vitriol that some describe, perhaps I am naive to stick up for those I don’t even know, but then again, us Old White Guys need to stick together (although others would say we do entirely too much of that).

Anyway, to answer the original question, I tune in to learn from others more knowledgeable and/or more experienced than myself. As well as to share my experience where I feel others might find it helpful. Have my posts ever been ego driven? More than likely. Have I recommended gear I own? Yes, on the basis of my experience. Hopefully, in the spirit of, here is what I found, your mileage may vary.

I find that most of the contributors speak in the same vein, and when absolutes are laid out, there is usually some solid experience, education, or training to back the claims up.

Like others I decry a peeing contest that some of these discussions devolve into. Perhaps, if we sense it coming, we can choose not to respond. Better to NOT have the last word than spoil the thread for all who come after. But then, many of us (myself included) are learning proper manners all over again in this digital age.

Recieved mine today. Going back tomorrow.  It was very nice to see my N-E reading is 0 on all circuits. But it is showing 102 on L-N for every outlet in my house.  L-N is currently 118 volts.  I have a monitor installed and check it every day.  So do I ask for a replacement or be happy I've played with it and move on. I'll decide tomorrow as I'm clicking the button.  I'm inclined to not trust it.




It's easy to check. Just use your multimeter and measure the voltage from either of the power contacts on a receptacle on the Niagara to the ground contact. If balanced power you will measure 60V nominal.

I am now down to <= 0.1  The poor old Fluke had been dropped one too many times.

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@ozzy @jea48  Very interesting that Niagara is balanced. Great job figuring this out.