Wiring Methods

The hole cut-out ready for a metal receptacle box. I held the face of the electrical box against the wall and penciled an outline to follow with my Drywall Saw.

Electrical Receptacle Box Installation in an Existing Wall Using Madison Bars

Click here for my post about installing an electrical receptacle.
A metal outlet box installed on wood lathe using small wood screws.

Install an Electrical Receptacle Outlet in an Existing Wall

Dear Mr. Electrician: I want to install an outlet on a dedicated circuit for my window air conditioner.  I've got it figured out how to run the 12/2 NM-B cable from the circuit breaker electrical panel in the basement up through the wall under the living room window.  How do I install an electrical receptacle box in the wall that will contain the wire and support the receptacle? Answer: Assuming that you will be drilling a hole from below and fishing the cable into the outside wall, the best place to cut a hole and mount a box is adjacent to a wall stud.  That way the box can be screwed through its side directly to the wood to make it solid. Locating a wall stud may not be that easy however.  I usually use an existing wall receptacle or switch as a reference.  If they were installed at the time that the house was built they are most likely mounted on wall studs.  I would remove the wall plate from the existing receptacle or switch and poke a long thin screwdriver to the right and to the left of the electrical box.  I would also push the box a little to see if it pivots.  Usually the side that is mounted to the stud will not move. Some of the applicable "National Electrical Code" references for this job are: Articles 210, 210.12, 250, 300.4, 310, 314, 334, 406.4(D)(4), 406.12, 440.6, 440.13, 440.31, 440.32, 440.62, 440.62(C), 440.63, 440.65. In newer homes with drywall I also look for indications of nail holes that were spackled over to find studs.  After I have a few studs located I measure over to the area where I would like to cut a hole for a receptacle.  In most home construction the wall studs are sixteen inches apart, but that is not always the case.  Sometimes wall studs are twenty four inches apart.  On some taller condominium buildings I have found the outside walls to have studs at twelve inches apart.  Measurement is from center to center and I always measure twice.  If I am lucky my measurement will correspond with a spackled nail hole which confirms that I have a stud.  Tool and material list below. On older homes with plaster walls it is not as easy to find a wall stud.  There are no indications of nail holes and sometimes outlets have been installed in the baseboard molding.  The use of electronic stud finders on plaster walls can be limited because of the inconsistencies of the old plaster keys and wood lathe.  In this situation the window itself may be the best indicator.  There should be at least one stud on each side of the window that goes from floor to ceiling. For walls with regular drywall you have a choice of using a one gang plastic old work box or a 2"x3" metal old work box.  Consult article 314 and table 314.16(A) and table 314.16(B) in the National Electrical Code for the proper size box for the...
A fiberglass fish rod is used here to fish a Type NM-B cable through a ceiling.

Fishing Wires in Walls and Ceilings Using Coat Hangers, Fish Tapes, and Rods

Dear Mr. Electrician: I don't want to spend a lot of money for special tools that I may only use once.  Can I use a metal coat hanger for fishing wires through a wall? Answer: My experiences with using metal wire coat hangers to fish wires through walls and ceilings have not been very good.  The metal used in the manufacture of coat hangers is a soft mild steel that bends easily.  When a coat hanger wire is pushed into a wall it becomes distorted and is not very controllable as to direction. A metal Fish Tape is made of hardened steel making it rigid and not very bendable.  There are also Fiberglass Rods made for fishing wires through walls and ceilings.  These are available in different lengths and thicknesses and are excellent for pushing through insulated walls. I do keep a piece or two of coat hanger wire in my truck.  One piece is about a foot long and bent into an L shape at each end.  One bent end extends approximately 3.5" and the other end extends approximately 2.5". Before I cut a hole in a wall or ceiling I will make a small hole (Around 1/4") with an Awl or a long thin screwdriver into the center of the hole to be cut.  First I insert a long thin screwdriver straight into the hole to probe for obstacles.  If I detect no obstructions I will insert the long thin screwdriver at a sharp angle in four different directions to feel for pipes, ducts, wood, wires or anything else that might inhibit the installation of something into the wall. My final step before cutting the hole is to insert the L shaped coat hanger into the wall or ceiling.  I push the coat hanger in and out while rotating to sense for obstructions.  I find that the coat hanger is particularly useful to detect anything that is up against the backside of the wallboard.  It is the best way that I have found to determine if Resilient Channel has been used to reduce sound transmission.  Because the Resilient Channel is against the backside of the wallboard it is difficult to detect when inserting a straight probe such as a screwdriver.  If there is insulation in the wall or ceiling you may find that it will inhibit the coat hanger and also cause it to bend as you push it in. I have also found it helpful to use a metal wire coat hanger to hook onto things inside of a wall or ceiling.  Sometimes I push my fish tape down a wall and it is just beyond my reach. A metal coat hanger with a hook on the end is pretty good at reaching inside of a wall to grab behind a wire or fish tape or even a fiberglass rod.  A metal wire coat hanger is a good tool to keep in your tool box along with other tools for fishing wires.  It comes in handy sometimes. Click here to read my post...
Wires in a hole awaiting the installation of an electrical box

Installation of an Additional Wall Dimmer and New Ceiling Light Fixture

Dear Mr. Electrician: Is it possible to install an additional dimmer next to an existing one and connect a new ceiling light to the new dimmer? Answer: Yes. However the methods used to achieve this type of installation will vary according to your building structure and the location of the switches and light fixtures. Below are photos of a simple dimmer and ceiling light installation in a condominium.
A very old style of GFCI receptacle.

Testing and Replacing a GFCI Electrical Receptacle

Dear Mr. Electrician: I push the "Test" button on my bathroom GFCI (Ground fault circuit interrupter) receptacle occasionally, but nothing seems to happen. How do I know if the GFCI receptacle is working properly? Answer: By pushing the "Test" button a simulated ground fault of approximately 6 milliamperes is shorted across the internal conductors and should cause the GFCI (Ground fault circuit interrupter) receptacle to stop working immediately. Normally you would hear a mild click sound and the "Reset" button might pop out a little. If the GFCI is not deactivated after pushing the "Test" button, the GFCI receptacle should be replaced as soon as possible because you are no longer protected against an electric shock or electrocution. Pushing in the "Reset" button should reactivate the GFCI receptacle. I have found that some "Reset" buttons need to be pushed in firmly using a blunt tool such as a screwdriver. Another method that I also use to test a ground fault circuit interrupter receptacle is with my Ideal Voltage Tester. I put one prong from the voltage tester into the ground pin opening and the other prong into the neutral side of the receptacle which should always be the larger slot. That usually trips the GFCI if it is working properly. If it doesn't trip, replacement is called for.  Unfortunately the new tamper resistant receptacles prevent me from testing this way so I use my plug-in tester instead. To replace the ground fault interrupter receptacle you should begin by shutting off the power to that particular circuit at the main circuit breaker panel or main fuse panel. Test the receptacle with a lamp, radio, or an electrical tester to make sure that the GFCI receptacle is without power. This may not be totally effective as it is possible that a non-working GFCI receptacle may not have power available regardless. Therefore you should proceed to the next step with caution and test the actual wires at the screw terminals of the GFCI receptacle using a voltage tester, a voltmeter or a pigtail light socket with a lightbulb. Remove the GFCI receptacle cover by unscrewing (Counterclockwise) the upper and lower screws on the cover plate. Next unscrew the upper and lower screws that secure the receptacle to the wall mounted electrical box. Carefully pull the GFCI receptacle straight out of the box as far as it will go. Take note of the wires connected to it. Look at the new Tamper Resistant GFCI Receptacle that you will be using to replace the old one. On the back you will see some words stamped into it. "Line" and "Load" are what you need to take notice of. Look at the back of the existing GFCI receptacle and take notice of which wires are on the "Line" and "Load" terminals. Normally the wires are white and black. Black on the "Line" side would be the hot wire that feeds into the receptacle. The white wire on the "Line" side is the neutral conductor that provides a path for the...
Front and Rear of an Old Style Pancake Box for Knob and Tube Wiring

Replacing a Very Old Style Ceiling Electrical Junction Box

Dear Mr. Electrician: I want to replace a very old ceiling light fixture in a very old house. After removing the existing light fixture ceiling canopy cover that hides all of the wiring, I found that there isn't a standard ceiling electrical outlet box. Instead, there is a black round disc (about 3 inches in diameter) which has a 1 inch long screw type rod sticking out of it. The wires are around it.  The light fixture that I want to install comes with a flat hanger bracket and the instructions tell me to install the hanger bracket onto the outlet box. Since there is no outlet box, I don't know what to do. What are my options? Answer: I suspect that the round disc is actually an old black enameled metal pancake box.  It's approximately the diameter and thickness of a hockey puck and made out of metal.  Sometimes an old gas pipe protrudes from the middle of this pancake box instead of a fixture stud.  A setscrew tightens the box to the gas pipe. (adsbygoogle = window.adsbygoogle || ).push({}); That was how old houses that originally had gas lighting converted over to electric lighting.  The pancake box was mounted onto to an existing disconnected gas pipe.  The cables were attached to the pancake box and splices were made.  An additional fitting or two was threaded onto the gas pipe to support the light fixture which was made for this type of installation.  The canopy of the old style ceiling light fixture acted as the junction box for the spliced wires. Other types of old pancake boxes were mounted directly onto ceiling joists using wood screws.  Instead of an opening for a gas pipe, they would have their own fixture stud for attaching a light fixture to.  The fixture stud had the same size thread as a gas pipe of the same diameter. Around the pancake box are four holes, each with a setscrew or clamp which engages the cable, preventing it from being pulled out, and provides electrical continuity for the equipment ground for the armored cable. The wiring is most likely armored cable (BX).  However ungrounded non-metallic cable (The Type Before Romex), or knob and tube type wiring is possible as well. Beware if the gas pipe has a cap on it. Usually the caps are removed when the gas line is taken out of service.  However, until you can verify that the gas line is dead you should not remove the cap. In a situation where the original wiring insulation has degraded, the best thing would be to install new wiring.  However that not only could be expensive, but damaging as well.  Walls and ceilings may need to be broken open to re-route or remove old dried and brittle cables and install new wiring. Turn off the power. You will need to remove the old pancake junction box.  Do it carefully so as to not damage the existing wiring.  Often, wiring from that era of home construction now has dry, brittle insulation...
The existing 2' x 4' fluorescent kitchen light fixture

Recessed Lighting in a Condominium Kitchen

Dear Mr. Electrician: I would like to replace the existing fluorescent light fixture in my condominium kitchen.  How difficult is it to install recessed lighting in a condominium and will it make a difference in appearance? Answer: The most challenging aspect of installing retrofitted recessed lights is the measuring and laying out of the location for each light.  With a finished ceiling there is no simple way of knowing what obstacles might be in the way of your light installation.  Therefore you must probe the ceiling ahead of time to see if there are any utilities where a light was planned.  Something to be mindful of is the fire rating of the ceiling if there is another condominium above yours.  Remodeling type recessed lights are usually not fire rated.  An alternative would be to install surface mounted LED disks on the ceiling which have a similar appearance to recessed, but mount directly onto a standard round electrical box.  Below are some photos of a recessed lighting installation in a condominium kitchen.
Three Way Switch Wiring Diagram

Three Way Switch Wiring Diagram

Dear Mr. Electrician: I have a set of Three-Way Switches in my house that have worked for many years without problems.  Now I find that one switch has to stay in the up position at all times just so the other switch will turn on the light.  How do I diagnose and fix this? Answer: I am guessing that one of the three-way switches broke down.  It can be a little tricky for an amateur to diagnose which switch died due to multiple wires being hot in this particular type of wiring.  I suggest that you change one switch.  If that doesn't fix it, then change the other one.  It's a good idea to replace both switches at the same time as the other one could fail soon after.  Be very careful to identify the line and load wires BEFORE you disconnect the switches. The LINE wire is usually the easiest to identify because it is hot at all times.  It should be terminated on a copper or black screw on the 3-way switch.  A Voltage Tester with a built-in continuity tester is good for testing the live or dead wires. All three-way switch wiring has the same basic components:  Wires consisting of a line, a load, a neutral, a pair of travelers, and two 3-way switches.  If you are trying to troubleshoot a 3-way switch operation, then you will need to identify the function of each wire.  Try to do this before you disconnect any wires from the switches.  Note the colors of the screw terminals on the existing 3-way switches.  The dark or red color screw is the most important to get right. Between each three-way switch or 4-way switch is a pair of "Travelers" which are connected to the common terminals.  On one of the 3-way switches a line or hot wire gets connected to the copper or black screw terminal.  On the other three-way switch the load wire gets connected to the copper or black screw terminal. Below is a simple diagram that can be applied to all three-way switch connections. There are several three-way switch wiring methods that can be used and it is usually the installer that determines what is the best way for his or her purposes.  The National Electrical Code now requires that a neutral conductor (White wire) be installed at most switch locations. I think that the most common method used to wire a set of 3-way switches is to bring the two wire line cable into one switch box and bring the two wire load cable into the other switch box.  A 3 conductor cable with a ground is then installed between the two 3-way switch boxes.  At the line switch box, the black wire of the two wire line cable gets connected to the copper or black screw terminal on the three-way switch.  The red and black wires (Travelers) of the 3 wire cable get connected to the common terminals on the three-way switch.  It doesn't matter which traveler goes on which common terminal.  The white line neutral wire gets spliced to the white wire of the three conductor cable.  At the other...
The finished ceiling mounted Wiremold surface box for the garage door opener

Wiremold for a Garage Door Opener Electrical Receptacle

Dear Mr. Electrician:  I need to install an electrical receptacle outlet on the ceiling of my garage for an electric garage door opener.  I do not have access to the ceiling from above as there is a bedroom located over the garage.  Any suggestions on how I may proceed with this? Answer:  In a few garages where there was already an electrical receptacle installed on the wall, I was able to install Wiremold surface metal raceway to bring power to a ceiling outlet. Below are some photos of a Wiremold installation that was used to replace an old extension cord that was powering the garage door opener.