A short stroll through house wiring history

Imagine back to the early 20th century. Home electrification in America was a new and somewhat frightening idea. What mixed feelings folks must have had - you could have electric lights, but you had to have wires running through your house. That stuff could catch your house on fire! But compared to kerosene lamps, it was easy to choose electricity. At least you didn't have to trim wicks and clean globes.

I remember the wiring in my grandmother's house. In the far corner of the attic there were porcelain spools on the wall. They held the fabric-covered electrical wiring that came into the house from outside. I've since learned that this is called “knob and tube wiring.”

Grandma's house had some old outlets and switches as well as some new. The old were more interesting because they were different from any I'd seen anywhere else. Most of her wall switches were today's rectangular flip-on-and-off type.

But there were a couple in out-of-sight places - in the stairway to the basement and the stairway to the attic - that were round. This kind of switch had a twist handle. A twist to the right turned the light on, and to the left turned the light off. For a kid, it made a seductively loud snapping sound in both directions. That kind of rotary switch was installed before the l920s.

There were old-fashioned outlets in Grandma's house, too. These earliest receptacles screwed into wall-mounted light sockets. How versatile! You could screw in either a light bulb or a receptacle to plug in something else. Either/or, not both.

Modern Outlets

Speaking of wall outlets, have you noticed that modern outlets have slots of different sizes? Early outlets had two identical slots. That's because electrification wasn't yet polarized.

Polarization means going to the trouble to keep the “hot” and “neutral” sides of electricity separate. Here's why that's important. Electricity comes from the power plant “hot.” It's packed full of energy and looking for some place to spend it. It's like the legendary cowboy on payday: If it doesn't find something constructive to do, it'll tear things up.

Hot electricity is the stuff that can hurt you. The constructive place for hot electricity to spend its energy is on a load.

A load is a consumer of electricity's energy. The load - such as a light bulb - turns the electricity into some other form of energy. The light bulb turns it into light and heat.

After electricity goes through the load, its energy is all gone. Going through the load has changed it from hot to “neutral.” Electricity leaving the load can't hurt you any more.

Have you noticed that on most plugs, one prong is bigger than the other? Most outlets are that way now, too. You can put the plug into the outlet only one way. The short outlet slot is hot electricity. The short plug prong leads to the “hot” side of the load.

Ah-ha! They're matched, and electricity goes where we need it to, not somewhere harmful.

The two-different-sized slots polarized outlet started appearing in homes in the 1920s. Wall switches were evolving as well, but flip-on light switches were a ways off.

Push button wall switches were used until the l940s. There were two buttons on the wall plate, one above the other. Push one to turn the light on, and the other to turn the light off.

Versions of the flip-on light switch started to appear in the 1930s. The kind we use now appeared in the 1950s.

And Then There Were Three

Back to wall outlets. In the 1960s, a third prong began to be put on the plugs of heavier appliances. So a third slot started to appear in home outlets. This third prong is for grounding (see my February 2005 column).

As with everything electrical, things may not be what they seem. It is easy to assume that everything is as it should be, but testing is a better idea.

It's easy to test a three-slot outlet for both polarity and grounding. You can use a simple three-prong tester that you plug into the outlet. It has three little lights. And there's a guide that tells you what the lights mean. For example, if you have two yellow lights, it means the outlet is correct.

The tester also will tell you if you have an open ground, open neutral, open hot, or if hot and ground are reversed, or if hot and neutral are reversed. If it turns out your outlet isn't correct, you could get a home repair book and try to fix it yourself. But I highly recommend you get an electrician. Why not spend a little of your money instead of a lot of your time, and make sure that it's done right? After all, we're talking about safety, not frills.

Most recently the GFCI receptacle has become required in certain places in the home. GFCI stands for ground-fault circuit-interrupter. GFCIs are required where there's likely to be water. That includes bathrooms, kitchens, garages, unfinished basements, crawl spaces and outdoors. The GFCI senses any tiny change in current and instantly turns off the power. You have to reset it to get power back.

Here's a tricky thing about GFCIs - you may have some that look like ordinary outlets. That's because a GFCI can be wired to protect everything forward from it in the circuit.

I ran into this when my downstairs bathroom outlet stopped working. Not bothering to do adequate troubleshooting, I replaced the outlet. The new one didn't work either, of course.

Later I discovered that my upstairs GFCI outlet also didn't work. “What's going on here?” I wondered. But this one was easy. I pushed “reset” and that fixed it. The amazing thing is that my downstairs outlet worked then, too. I guess Grandma was right - if you leave some things alone, they fix themselves.

Alas, most things don't fix themselves. But some things are easier to fix than we might think. Updating circuits doesn't always require re-wiring. For example, often GFCI outlets can be installed with ungrounded wiring, and give even more safety.

And when it comes to actually doing the work, weigh your money vs. your time and safety and consider an electrician.