Line fault at the outlet -- do I need an electrician?

Yesterday, I got a Panamax, Max 1500 surge protector and line conditioner. (I got a very good deal on it, and am just trying it out.)

I plugged it into an outlet I've been using for a while and one of the red lights on the front lit up saying "line fault." (I'm not sure how this is different from a "ground fault." Maybe it's the same.) The Panamax does not do this with other outlets in the room. They seem ok.

So, I know this means that the outlet is improperly wired. My question is, might this be a simple thing to check and/or fix? Any suggestions most appreciated. It's the only outlet I can use to have my audio set up where I usually have it. Now is not an optimal time to call an electrician. If this is a big problem, I'll try out my gear somewhere else in the room, but if I can fix this without too much expertise, that would be ideal.
8700e65e 845e 4b1b 91cc df27687f9454hilde45
@ hilde45 OP

Yeah, you got a lot going on there. And all that on #14awg wire to boot. It’s been like that, I imagine, for many years and you didn’t know it. That is, unless the 15 amp breaker was tripping occasionally from being overloaded.

You didn’t know the AC polarity was reversed at the wall outlets either, until several days ago. (Not mentioned in this thread, reversed AC polarity can have an affect on the sound of an audio system. But that’s for another thread.)

As for the 4 volts you measure from the neutral to the equipment ground that really doesn’t matter. The 4 volts may not even really exist. It could just be phantom voltage created by the multimeter. Even if the 4 volts is real it’s to low to be an electrical safety/shock hazard.

This all started because you bought a ’ Panamax, Max 1500 surge protector and line conditioner’. Then when you plugged it in it said you had an AC mains line fault. If you hadn’t bought the darn thing you wouldn’t have been going in circles the last several days trying to figure out what the problem is.

Options, the way I see it.

1) There is way to much going on with the branch circuit wiring for you to repair. Not to mention your qualifications.... You maybe a great teacher, but a lousy electrician... An electrician could spend a couple days, maybe more, straitening out the mess. It all comes comes down to time and money. You have the money, he/she has the time.

2) Reverse the Hot and neutral wires at the duplex receptacle outlet the power conditioner will be fed from. I assume the duplex outlet is used to feed all of your audio equipment.

3) If all of your audio equipment will be plugged into the power conditioner you could reverse the Hot and neutral wires on the power cord plug of the cord used to feed the power conditioner.

4) Hire an electrician to install a new 20 amp dedicated branch circuit for your audio equipment.

There are instances where reversed AC mains polarity can be an electrical shock hazard. In the case of screw in light sockets. If the mains polarity is reversed and the circuit is hot, on, feeding the light socket the outer screw shell of the socket will be Hot with respect to ground. To lesson the likely hood of receiving an electrical shock in the event one hand is in contact with the outer shell of the light bulb, while it is in contact with the shell of the light socket, and the other your other hand is touching a grounded object MAKE SURE the switch is in the off position. If the light has a cord and plug you can always just unplug it from the wall when replacing a burned out light bulb with a new one one.


Jim, all,

Thanks SO much for sticking it out on this detective inquiry!

The 4v issue is weird, because the multimeter does not read 4v on a properly wired outlet on a different circuit.

I'm glad the Panamax revealed the issue, though, especially if there's a safety issue.

Thanks for the options. (1) & (4) are the most attractive and would tie in with an electrician, but won't happen for a while.

(2) Reversing seems possible. QUESTION: Is it safe to have one reversed outlet? I guess I don't see why not, but I just want to make sure I am understanding.

Thanks for the hint about changing the light bulb. In sum: either (a) unplug the lamp or (b) make sure it's off before changing the bulb.

hilde45 OP303 posts


The 4v issue is weird, because the multimeter does not read 4v on a properly wired outlet on a different circuit.
Apple to oranges, imo.
What is the wire gauge size of the other branch circuit? What is the total length of the branch circuit? What is the total connected load on the circuit? What is the type of devices that are connected to the circuit? How many CFL and or LED lights are connected to the branch circuit? What is the voltage drop on the circuit that you didn’t measured the 4V neutral to ground voltage?

You have all kinds of things going on with the branch circuit where the wall outlets have reversed polarity issues. You now know the branch circuit feeds outlets on the first floor and the basement. You now know it feeds ceiling lighting. How many CFL and or LED lights? They spew all kinds of harmonic noise back on the AC mains. Who knows what that does to your cheap multimeter.

There is still a very good chance the 4V is caused by voltage drop. Now that you know the branch circuit feeds outlets and ceiling lighting on the first floor, not just the basement, turn off all the connected loads that are connected to the branch circuit. Check for the neutral to ground voltage again. No load, no voltage drop.

As for the power conditioner showing an AC mains ’Line Fault’ condition. Correcting the AC polarity reversal problem, will solve the power conditioner 'Line Fault' problem.

Got it. All those are good questions, but I think the ultimate solution is to delegate this whole thing. But now I know what to ask the professionals. This amateur is sticking with writing and teaching. Thanks again.
"I remeasured the outlet. Here are the readings that I got:
Ground to neutral slot equals 121.6ground to hot slot equals 3.6
neutral to hot equals 124.6Hot to neutral equals 124.6"
- Hot to Neutral 124.6   (let's call Hot - Line .. more typical term)
- Ground to Neutral Slot 121.6- Ground to Line Slot 3.6
I assume this measurement was made with almost everything turned off?
Hot-Neutral is 124.6 ... or about the same as Ground-Neutral + Ground-Line.  With a noise-free reading, (G/N) + (G/L) should approximately equal the source voltage at your electrical panel AND and should be higher than what you measure L-N at the outlet.

(G/N) + (G/L) = 125.2 - Or perhaps the voltage at the panel(L-N) = 124.6 - Or the voltage after all the drop(G/N) + (G/L) - (L-N) = 0.6

However, as stated G-N should be close to 0, but often is not due to drops in the wires (and noisy measurements). Given you have 3.6 with what appears a very small drop on L-N, that suggests either a noisy measurement (possible), OR, it could be a faulty ground connection on that line. Given the wiring issue already noted (and DIY nature), I would be investigating the ground integrity. Fortunately, you can do this yourself.

1) Turn the breaker off!!2) Wait 30 seconds (any leakage from capacitors in power supplies)3) Ensure the L-N, G-L and G-N voltage is 0.  I am expecting G-N is 0, but if it is not really close with power disconnected, that is an interesting result. If it is no 0 or really close, DO NOT CONTINUE!
4) Repeat step 3! ... you really need to be sure.5) Put your multi-meter on the ohms setting.6) Measure the resistance between the Ground and the Neutral (the ones that was measuring 3.6 volts). It should be <1 ohm with a good contact between the probes and the socket.