Basic Electrical Repairs for Building Maintenance
Prove a circuit is dead, reset breakers and GFCIs, replace outlets, switches and lamps, and know which electrical work to leave to an electrician.
Table of contents
Electrical work is where knowing your limits matters most. Small jobs come up every day: a tripped breaker, a dead outlet, a flickering light. These are normal maintenance tasks, and you can do many of them safely if you are trained and authorized. Anything beyond that, such as panel work or new circuits, belongs to a licensed electrician. Rules for maintenance workers differ by state and employer, so find out what you are allowed to do before you open a cover. Never do any of this work unless you have been trained and your employer has authorized you.
What You Will Be Able to Do
- Use the test-verify-test method
- Tell an overload from a short circuit
- Find the cause of a dead outlet
- Replace an outlet, switch, or lamp
- Know when to stop and call an electrician
Prove It Is Dead
Lock out the breaker, tag it, and follow your site's lockout procedure. Then test. Do not rely on a label on a panel. Labels are often wrong.
Test-Verify-Test
- Test the tester on a known live source, so that you know it works.
- Test the circuit you will work on. Check every wire in the box, since some boxes hold more than one circuit.
- Test the tester again on the known live source. If it died, a dead reading means nothing.
A non-contact tester is good for a quick check, but it can miss things. Use a two-lead tester for a real proof of dead.
Warning: Do not work inside a live panel. Do not bypass a safety device or use a larger breaker or fuse to solve a trip. Report burning smells, sparks, warm outlets, and scorched wires right away.
Breakers
A breaker trips to protect the wires. A trip is a message, so find out why it happened.
The most common cause in a commercial space is an overloaded circuit, with too many devices drawing power. Space heaters, coffee makers, and printers are usual suspects.
Resetting a Breaker
- Find the tripped breaker. It may sit between on and off.
- Push it fully off, then back on.
- If it stays on, look for what caused it.
When It Will Not Reset
If a breaker refuses to reset or trips right away, there is probably a short circuit still present somewhere downstream. Do not keep resetting it.
| What happens | Likely cause | What to do |
|---|---|---|
| Trips only when many devices run | Overload | Move loads to other circuits |
| Trips as soon as one device starts | Device fault | Unplug the device and tag it |
| Trips with everything unplugged | Wiring fault | Call an electrician |
| Will not reset at all | Short or a failed breaker | Call an electrician |
Worked example. A 15-amp circuit in a break room feeds a 1,500-watt microwave and a 1,200-watt toaster. Amps equal watts divided by volts. 1,500 plus 1,200 is 2,700 watts, and 2,700 divided by 120 volts is 22.5 amps. That is far over 15 amps, so the breaker trips. Move one appliance to a different circuit.
GFCI Outlets
A ground fault circuit interrupter (GFCI) shuts off power when current leaks away from its normal path. These outlets protect people in wet areas, such as restrooms, kitchens, garages, and outdoors. A GFCI outlet has Test and Reset buttons.
One GFCI can protect other outlets downstream on the same circuit, and that surprises people. A dead outlet in one restroom may be fed by a GFCI in another restroom, or in a garage or outdoors.
Dead Outlet Checklist
- Look for a tripped GFCI on the same circuit, even in another room. Press Reset.
- Check the breaker.
- Plug in a tester or lamp to confirm that the outlet is dead.
- If a GFCI will not reset, and the breaker is on, it may need replacement, or there may be a fault downstream.
Press the Test button on GFCIs on a regular schedule, as the maker recommends.
Replacing Outlets and Switches
Do this only if you are authorized, and only for a like-for-like swap.
- Lock out the circuit and prove it dead.
- Remove the cover plate and the device screws.
- Pull out the device and photograph the wiring.
- Check the wires. Stop if you see scorching, or aluminum wire, or more wires than you expected.
- Connect the new device the same way. Black (hot) goes to the brass screw, white (neutral) to the silver screw, and bare or green (ground) to the green screw.
- Fold the wires back neatly and fasten the device.
- Install the cover, restore power, and test.
Match the amp rating and type. Outlets in wet areas need GFCI protection, and some areas need tamper-resistant outlets.
Three-way switches, dimmers, and occupancy sensors each have their own wiring. Follow the instructions, and take a photo first.
Lighting
Fluorescent Tubes
- Turn off the switch.
- Rotate the tube a quarter turn and lower it.
- Install the new tube, rotate it to lock, and test.
Fluorescent tubes contain mercury. Recycle them under your site's rules, and do not throw them in the trash. If a tube breaks, follow your cleanup procedure.
Ballasts
If new tubes flicker or stay dark, the ballast may be failing, and you may hear it hum. Lock out the circuit, follow the wiring diagram on the new ballast, and take a photo first. Very old ballasts can contain PCBs, which are hazardous. If one is leaking or was made before the 1980s, stop and ask.
LED Conversions
Many buildings are converting to LED. Some LED tubes plug straight into the old fixture. Others bypass the ballast and connect line voltage to the sockets. If a fixture has been converted, it needs the label that comes with the kit, so that nobody installs the wrong lamp. Follow the kit's directions.
Emergency Lights
Exit signs and emergency lights have batteries. If one fails its test, replace the battery or the unit and record it.
When to Call an Electrician
Stop and call if you see:
- Anything inside a panel
- A new circuit or a moved outlet
- Scorched or brittle wires
- Aluminum wiring
- A breaker that trips over and over with no clear cause
- Water near electrical gear
- A shock from any metal surface
If a person is getting shocked, do not touch them. Shut off the power first if you can, and call 911.
Finishing the Job
Remove your lock only after everyone is clear. Test the repair. Replace any cover you removed, since an open box is a hazard. Record the circuit, the part, and what you found in your work order. If you found a wrong label on the panel, fix it or report it.
Common Mistakes
| Mistake | What it costs |
|---|---|
| Trusting the panel label | A shock from a live wire |
| Skipping the second test of the tester | A false dead reading |
| Resetting a breaker over and over | Overheated wires and a fire risk |
| Replacing a breaker with a larger one | Wires that can overheat |
| Skipping the search for a GFCI | Replacing an outlet that was fine |
| Leaving a converted fixture unmarked | A wrong lamp and a shock risk |
Check Your Understanding
1. What are the steps of the test-verify-test method?
Test your tester on a known live source, test the circuit, and test your tester again on the known source.
2. An outlet in a restroom is dead, but the breaker has not tripped. What do you do?
Find the GFCI on that circuit, which may be in another room, and press Reset.
3. A breaker in the break room trips each morning around 8. What do you suspect, and what do you do?
An overload, from several appliances running at once. Work out the load, and move something to another circuit.
4. A breaker will not reset, even with everything unplugged. What is likely wrong?
A short circuit is still present in the wiring, or the breaker has failed. Call an electrician.
Key Takeaways
- Lock out, tag, and prove dead before you touch anything.
- Test your tester before and after you test the circuit.
- Overloads are the most common cause of trips. Shorts stop a breaker from resetting.
- A dead outlet is often a tripped GFCI in another room.
- Do like-for-like swaps only, and leave panels and new circuits to electricians.