This tutorial shows how to replace a worn-out electrical outlet and explains best practices for wiring an outlet.
Electrical Outlet Hissing Noise
Electrical outlets are taken for granted until they don’t work. I started paying attention when the kids said the 1500 watt DeLonghi electric oil filled radiator space heater used to keep the bathroom extra warm wasn’t working. I checked the heater and there was no power, however I could hear a faint hissing or sizzling noise coming from the outlet. The heater plug was very loose in the outlet and the hissing noise changed as I wiggled the plug. I pulled the plug and the blades were pitted and corroded with a rough grayish film from electrical arcing and the plastic face of the outlet was melted slightly from the plug blade. A 1500 watt heater pulls 12 AMPS of current – and that’s a lot on a typical 15 or 20 AMP household circuit.
The problem was obvious: the electrical outlet was worn out from 10+ years of daily use. The metal contacts inside the outlet weren’t holding the heater plug securely and electricity was arcing across the slight gap between the loose plug and the outlet. The gap between the metal contacts causes electrical arcing – the sizzling or hissing noise – and a high resistance connection which heated the plug blades and melted the outlet face. If left alone, the outlet can get hot enough to start a fire.
I immediately replaced the electrical outlet with a new one and buffed the gray corrosion off the heater plug with some sandpaper. The space heater works great now.
I didn’t think to keep the worn out electrical outlet to show you here, thinking it was a rare circumstance not worth mentioning. However, as I inspected the most heavily used electrical outlets in the house I found several which were getting worn out and plugs were loose. The loose plug would often back out exposing the plug blades from the weight of the electrical cord. The bathroom and hallway plugs are the most used and abused. Think about everytime the vacuum cleaner is plugged into the hallway outlet and the cord is jerked and pulled to its full length as you work from room to room until the plug pops out. This stresses and opens the metal wipes inside the outlet over time causing a loose plug.
Replacing an Electrical Outlet
This outlet by the bathroom sink was showing definitely signs of wear and wasn’t holding plugs securely. To replace the outlet, I began by:
- Plugging in the receptacle tester which illuminated two yellow lights indicating the receptacle is wired correctly.
- Shut off the electricity at the circuit breaker in the main electrical panel.
- Observed the receptacle tester lights are not illuminated confirming the outlet is not powered.
When using a receptacle tester, you must test the outlet before shutting off the power because no lights on the tester can indicate an “Open Hot” condition. I could’ve used my standard voltage tester here, but since I’m wiring a new outlet the receptacle tester is more convenient.
Remove the Old Electrical Outlet
Remove the faceplate screw and white faceplate, then remove the two receptacle mounting screws to release it from the wall box.
Pull the electrical outlet forward from the wall box to expose the wiring:
Several things are apparent from the way this outlet is wired:
- Because this outlet is in the bathroom, it’s on a 20AMP circuit with NM-B 12/2 (12 gauge, 2 conductor plus ground) wire protected by a Ground Fault Circuit Interrupter (GFCI) outlet (not shown) elsewhere in the circuit. 12 gauge wire is required for a 20AMP circuit.
- The outlet itself is rated for 15AMPs / 125 volts, this is fine and complies with the National Electrical Code.
- The outlet is “sidewired“, meaning the hot (black) and neutral (white) wires are fastened to the side screw terminals. (The black wires have some spray paint them from when the builder painted the walls.)
- The outlet is a “middle of the run” wired in “series” – meaning current passes between the side terminals to the next outlet down the line. This is common practice, but parallel wiring with a “pigtail” is better.
- The electrical wiring extends well beyond the minimum requirement of 3 inches beyond the wall box.
- The outlet is properly grounded via the bare ground wire that is tied via a pigtail to the cable ground wires.
In brief, this outlet is properly wired.
Series versus Parallel Electrical Outlet Wiring
The following electrical outlet wiring diagram illustrates a middle-of-the-run outlet wired in series. The outlet in the above photo corresponds to the left and middle outlets in the wiring diagram. Series wiring is quicker and simpler compared to parallel wiring, however any problem with a middle-of-the-run outlet will affect all downstream outlets, i.e. outlets to the right of the bad outlet.
Wiring electrical outlets in parallel with pigtail connections that are twisted and nutted together is a more reliable method which isolates the outlet from the current path, thereby reducing the chance that a problem with the outlet will affect the other outlets on the circuit. Parallel outlet wiring is illustrated in this diagram:
Disconnect the Outlet Wiring
The wires can be removed from the worn out outlet by:
- Loosening the side terminal screws, opening the looped wire end with screwdriver tip and sliding it off the screw terminal. This is the preferred method if you’re going to sidewire the replacement outlet.
- Or simply snipping off the wires with wire cutters as shown here.
I chose to snip off the wires because I’m going to backwire the replacement outlet and I have plenty of wire extending from the wall box. Backwiring requires straight wire ends and I couldn’t be bothered to straighten the looped ends with pliers.
Do not cut your wires if the leads extend less than 3 inches beyond wall box.
Electrical outlet after cutting off the wires.
This project is continued in Part 2.
Thanks for reading,
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