Peter McCarthy Electric Co., Inc. - Specializing in Older Buildings in Chicago
Adventures in Old House Wiring....

Follow-up ltter to a phone inquiry

A lady telephoned a few weeks ago to ask "how soon I could come out." The first question many people ask. In this case, soon was not soon enough.I asked her what the issue was, and after about 20 minutes or so we had walked all the way though the steps she could take herself. It was a very simple operation, really.  If I recall, she wanted to change a dimmer. I asked her her comfort level with this kind of thing. Since she had said she had already changed one switch, she seemed like the type of person who could easily replace a dimmer, taking the proper precautions. She was able to change it herself, I was able to share a little knowledge and empower a young homeowner, and off course she saved on an electrician's service call.
Here is a copy of the follow-up email I sent her. It includes valuable info for all you DIYers out there!

Hi J;
It was a pleasure "meeting you" over the phone yesterday. I am so pleased you had success with this project. It is a really good "Hey I did that!" feeling, isn't it? Plus it keeps a few dollars in your pocket!

The main things to always remember are:
1. Neutral wires carry current, not voltage. They can be even more dangerous than hot wires. ALWAYS TURN EVERYTHING OFF.
2. Breakers are often not identified properly. You might think you are turning a specific circuit off when you are not. ALWAYS TURN EVERYTHING OFF.
3. When you put in outlets or switches, (when power is dead, of course) take the time to wrap the metal screws where the wire attaches with electrical tape. That insulates them from accidental human shock down the line, or shorting the circuit if a grounded or hot wire gets inadvertently pushed up against them and makes accidental contact, especially likely in very crowded switch boxes.
4. These are the basic color codes for wiring in Chicago:
-neutral wire
- neutral wire
red, black
-hot wires. these will always be hot, or live, when the breaker is on. They supply the power to outlets, switches, ect.
blue, yellow, orange
- switch legs  (wires that attach to the switch so they become hot when the switch is turned on, and they lead to the light fixture or whatever the switch is controlling. when the switch is off, they should be dead, or off.
purple, brown
- depends on situation. Not that common. Assume they are"hot" until proven otherwise.

Those are the basic color codes that electricians are supposed to follow. But at times they don't.  A white could be "hot" and a black could be neutral. Electricians and handymen sometimes use the color wire they have, if they are missing the correct one. I always use colored tape to identify the wire in such a case. If I am all out of white wire, I can use red wire as long as I clearly identify it with white tape. But they often don't. SO ALWAYS TURN EVERYTHING OFF.  (starting to see a pattern here?)

One other situation you may encounter. Folks use BX cable where there is no pipe. That cable comes factory-manufactured with a white and black wire in it. Newer BX has a green wire also. It also comes with 3 wires, white, black, red. But it is really common for folks to use a 2-wire BX to add a switch to a light that was previously a pull chain. In that case they fish that 2-wire BX down the wall to a switch box, and add the switch. Since there is only white and black to work with, they usually use the black as the hot to feed the switch, and then the white is used as the switched wire back up to the fixture. (The code actually allows this but I don't agree with the practice.)  But you should be aware of it for safety. It happens more in older homes. Where you find just 2 wires in a switch box, one going to each side of a switch, and they are black and white, the white is NOT a neutral. It will be hot when the switch is turned on!

Well I hope that information keeps you safe and helps you out in the future. Even if you don't do anything more complicated than yesterday, knowledge is power, right? Just remember, ALWAYS turn EVERYTHING off. A little excess in the name of safety is well worth it. You can reset your clocks when you are done.

Best wishes and always feel free to call if you need advice or a second opinion.

Most sincerely;


Peter McCarthy, President
Peter McCarthy Electric Co., Inc.
Chicago, IL 60615
Office:   773/947-9145
Mobile:  773/842-3649
Angie's List Super Service Award  2003, 2008, 2009, 2010, 2011, 2012
Member, Electrical Section, National Fire Prevention Association
Hyde Park Chamber of Commerce

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