In my new house (well, it's an old house, 58 years old) when I plug my Uninterruptible Power Supply into the mains so it can feed power to my computer and all the peripherals, the little red light on the front lights up, "Building Wiring Fault".

What does this mean? Everything appears to work normally. Is it dangerous? Is it something that I need to attend to? Am I risking damaging my equipment?

My electrical knowledge is pretty limited. I'm a wizard when it comes to flipping a light switch, but that's about as far as it goes.

tanstaafl.

Could be that there's no dedicated ground, only a hot and a neutral wire. Only the newer homes here are wired with three wires. In fact, you can't even buy romex with three wires at Home Depot...they don't sell it. So even if it's a three-prong outlet, you may want to pull it out and see if it's wired with a ground wire.

With all concrete walls, running a ground wire all the way back to the electrical panel and then putting in the proper ground there might be really complicated. Then again, since you own the house, it might be worth the effort. I'd consult an electrician. The work here is so cheap, it'd definitely be worth it.

The other possibility is that the polarity is reversed by connecting the wires to the wrong terminals on the outlet (hot to neutral and neutral to hot).

Depending on how smart it is, it could be indicating:

No ground, as above.

Ground and neutral swapped.

Live and neutral swapped.

No neutral (very unlikely, I suspect, but not impossible.)

You can get little plug in widgets which will show on lights which of these is the case, as well as other issues. Something like this for example.

I'd suggest it's something useful to have in your toolkit as a general test device. The most likely probability is lack of a ground, but any of the others are possible and can cause a hazard if something goes wrong.

pca

To answer your question about whether you're risking damage, the answer is "yes". Everything could work perfectly normally until you get a big power surge or a lightning strike, at which point the surge protection circuitry in the UPS won't function properly. No bueno.

Now ordered.

tanstaafl.

Hopefully you ordered something compatible with Mexican mains?

EDIT: Ah.. same as Canada, compatible with USA too. No problem!

I checked that it was compatible first just in case

pca

Here is what the clever little device had to say. I got the same readings from different outlets in different parts of the house, except for one room which shows two green lights and no red whether or not the button is pressed.

Attached are two files, one of the line checker in action, and another of the very detailed instruction manual which I had to scan in at 600 dpi and then quadruple the dimensions of the image to make the text large enough to read.

So now the question is: What is my next step?

tanstaafl.

Open ground, as I initially guessed.

The button isn't useful unless you're testing a GFCI outlet, so just ignore it.

I'm no electrician, but as I understand it, you'll need to run a ground wire from each outlet that you want to be properly grounded to your electrical panel. Then inside the panel, If I understand correctly, the ground bus should be bonded to the neutral bus, and also connected via a grounding wire to a 8 ft copper rod that's driven into the ground. Any electrician should know what to do and would be incredibly cheap by US standards. The hairy part is what's involved in running that wire from point A to point B.

Also, any outlet that you don't want to run a ground wire for should be switched back to a two prong outlet or labeled so that people don't mistake it for a grounded outlet.

I did not look at the instructions, but I have used similar testers many times.

First note: The GFI fault tester button cannot perform its test function unless there is a ground circuit connected to the outlet. Without a ground, the test button just creates an oddball light pattern on the tester.

The single green light (when the test button is not pressed) indicates the outlet has AC power, but there is no ground connection to the outlet. If there was a ground connection, a second light would illuminate.

As anticipated, it appears your house is wired without grounding to the outlets. This is also what the UPS ‘wiring fault’ indicator is complaining about.

Next step? Well, if you wish to avail yourself of the additional safety and safeguards that a ground connection offers, somehow a proper ground wire needs to connect between the green screw on the back of the wall receptacle, and to an actual electrical ground point.

How this might be done would be specific to your house configuration, and to what the local electrical codes allow.