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BUS-APPL73-02 · Lesson 1 · 10 clock hours · theory

Electrical Safety and Lockout/Tagout for Appliance Work

Objective. Students will correctly identify electrical hazards present in residential appliances and execute a complete lockout/tagout procedure on a de-energized appliance before any diagnostic work begins.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a credentialed professional in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Why Electrical Safety Comes First

Appliance repair technicians work on equipment that operates on 120 V AC, 240 V AC, and in some cases stores dangerous energy even after the plug is pulled. A residential electric range, for example, draws up to 50 amperes at 240 volts. Contact with energized conductors at those levels can cause ventricular fibrillation, severe burns, or death in fractions of a second. Before you touch any internal component of any appliance, you must eliminate every source of hazardous energy. That process is called lockout/tagout, and it is not optional.

The Legal Standard: OSHA 29 CFR 1910.147

The federal regulation that governs lockout/tagout in workplaces is OSHA 29 CFR 1910.147, known as the Control of Hazardous Energy standard. It requires that any machine or equipment capable of unexpected energization or release of stored energy be isolated and rendered inoperative before a worker performs servicing or maintenance. Although the standard was written with industrial equipment in mind, the same hazards exist in residential appliances, and reputable employers apply 1910.147 principles to every service call. Understanding this standard is part of the PSA Certified Appliance Professional body of knowledge and is tested on that exam.

Key requirements from 1910.147 include: developing a written energy-control program, training affected and authorized employees, using proper lockout/tagout hardware, and verifying that energy has been released before work begins.

Energy Sources in Residential Appliances

Not all energy sources in an appliance are obvious. You must account for every one of them:

The Six-Step Lockout/Tagout Procedure

Memorize and practice these steps in order. The competency check for this lesson requires you to perform all six without prompting.

1. Identify all energy sources. Before touching anything, inspect the appliance and identify every form of energy it uses—electrical, stored (capacitor), and any other relevant source such as gas. Consult the appliance's wiring diagram if available.

2. Notify affected personnel. Inform anyone working nearby that the equipment is being taken out of service.

3. Shut down the equipment. Use normal stopping procedures (power button, control panel) to turn the appliance off.

4. Isolate the energy source. Unplug the appliance from the wall outlet, or open and lock out the circuit breaker that feeds it. For a 240 V range hard-wired to a panel, lock the breaker in the OFF position using a breaker lockout device.

5. Apply your personal lock and tag. Attach your personal padlock to the lockout hasp at the isolation point. Attach a tag that includes your name, the date, and the reason for lockout. Only you may remove your lock.

6. Verify zero energy (release stored energy and test). Press the appliance's power button to confirm it does not start. Then use a non-contact voltage tester as a quick screen, followed by a digital multimeter set to AC voltage to confirm zero volts at the terminal block or internal wiring harness. For appliances with capacitors, follow the manufacturer's discharge procedure before touching those components. Sign and date the de-energization log.

Using Your Test Equipment Correctly

A non-contact voltage tester (NCVT) detects the presence of AC voltage without touching conductors. It is a fast screening tool, but it can miss voltage on shielded or tightly bundled wires. Always follow up with a digital multimeter (DMM) set to AC voltage.

When using the DMM: insert the black lead into the COM jack and the red lead into the voltage jack. Select AC voltage (VAC) at a range above the expected voltage—for 240 V circuits, select a range of 300 V or higher if the meter is not auto-ranging. Test between line and neutral, line and ground, and line-to-line on 240 V equipment. A reading of 0 V AC on all combinations confirms de-energization.

Always verify your meter is working before and after the test by checking a known live outlet. A meter with a dead battery or a blown fuse can read zero on a live circuit—a fatal mistake.

Personal Protective Equipment

Wear safety glasses whenever you are working near electrical components. Before testing at any point before you have confirmed zero energy, wear insulated gloves rated for at least 1,000 V. Inspect gloves for cuts or pinholes before each use. PPE is your last line of defense; the lockout/tagout procedure is your first.

What the Case Studies Tell Us

Investigation summaries from CPSC and OSHA repeatedly show the same patterns in appliance-related electrical accidents: the technician assumed the appliance was de-energized without verifying, or lockout hardware was skipped because the job seemed quick. There is no such thing as a quick job when the consequence of a mistake is cardiac arrest. Every repair begins with a complete lockout/tagout, every time.

Key terms10

Lockout/Tagout (LOTO)A safety procedure that uses physical locks and warning tags to isolate hazardous energy sources and prevent unexpected re-energization of equipment before servicing begins.
OSHA 29 CFR 1910.147The federal OSHA standard titled 'Control of Hazardous Energy,' which establishes minimum requirements for lockout/tagout programs in workplaces.
Authorized EmployeeUnder 1910.147, the worker who actually applies the lockout/tagout device and performs the servicing; responsible for the entire lockout procedure.
Stored EnergyEnergy retained in a component—such as a charged capacitor—that can cause injury even after the main power source has been disconnected.
Non-Contact Voltage Tester (NCVT)A pen-shaped device that detects the presence of AC voltage through induction without touching conductors; used as a quick initial screen but not a substitute for multimeter verification.
HaspA multi-hole lockout device that allows more than one padlock to be secured to a single isolation point, ensuring no single person can restore power while another worker's lock is in place.
De-energizationThe process of disconnecting and verifying the removal of all hazardous energy from an appliance prior to performing diagnostic or repair work.
Capacitor DischargeThe deliberate and controlled release of electrical charge stored in a capacitor using an appropriate discharge tool or resistor, required before handling components near the capacitor.
240 V AC (Split-Phase)A two-pole residential supply voltage formed by two 120 V ungrounded conductors that are 180 degrees out of phase; used for high-wattage appliances such as electric ranges and dryers.
PPE (Personal Protective Equipment)Equipment worn to minimize exposure to hazards; for electrical appliance work this includes safety glasses and insulated gloves rated for the voltage present.

Worked examples4

1. You are about to diagnose a faulty surface element on a hard-wired 240 V electric range. List and explain every isolation and verification step you must complete before touching the terminal block.
  1. Step 1 – Identify energy sources: The range runs on a 240 V AC two-pole circuit from the panel. Note the wiring diagram location of the terminal block and any capacitors on the control board.
  2. Step 2 – Notify affected personnel that the range is being taken out of service.
  3. Step 3 – Shut down the range using its normal controls (turn all burners and the oven to OFF).
  4. Step 4 – Go to the electrical panel, locate the dedicated two-pole breaker for the range, and move it to the OFF position.
  5. Step 5 – Attach a breaker lockout device over the breaker handle and secure your personal padlock through it. Attach a tag with your name, date, and reason.
  6. Step 6 – Return to the range, press the surface element control to verify the element does not heat and the display does not power on.
  7. Step 7 – Use the non-contact voltage tester near the terminal block wiring to screen for voltage.
  8. Step 8 – Set the DMM to AC volts at a range above 240 V (or auto-range). Verify the meter works on a known live outlet first. Test: Line 1 to neutral = 0 V, Line 2 to neutral = 0 V, Line 1 to Line 2 = 0 V, each line to ground = 0 V.
  9. Step 9 – Confirm all readings are 0 V AC, then sign and date the de-energization log.
Answer: All four conductor-pair combinations (L1-N, L2-N, L1-L2, L1-G, L2-G) read 0 V AC on the DMM, the range does not respond to controls, and the de-energization log is signed. It is now safe to work on the terminal block.
2. A technician unplugs a top-load washer from its 120 V outlet. Before opening the cabinet, what two instrument checks must be performed, and at which points on the appliance?
  1. Step 1 – Unplug the washer from the wall outlet. This is the energy isolation step.
  2. Step 2 – Apply personal padlock and tag to the outlet or plug retention device (or in a shop setting, use a plug lockout device on the cord plug).
  3. Step 3 – Press the washer's power/start button to confirm the machine does not attempt to start.
  4. Step 4 – Use the non-contact voltage tester: hold it near the power cord at the machine end and near the motor wiring harness inside the cabinet (if accessible without removing panels) to screen for residual voltage.
  5. Step 5 – Set the DMM to AC volts above 120 V. Verify meter function on a known live source first. Probe the two terminals of the internal power cord connector (or terminal block) inside the washer: measure line to neutral = 0 V AC and line to ground = 0 V AC.
  6. Step 6 – Document 0 V AC readings on the de-energization log and sign.
Answer: Both instrument checks—NCVT screen and DMM measurement of 0 V AC line-to-neutral and line-to-ground at the internal power connection—confirm de-energization. The washer is safe to open for diagnostics.
3. A refrigerator uses a 120 V AC supply and has a motor-start capacitor on the compressor. After unplugging, why is a zero-voltage DMM reading alone not sufficient, and what additional step is required before touching the capacitor or nearby components?
  1. Step 1 – Unplug the refrigerator and apply lockout/tagout to the plug.
  2. Step 2 – Use NCVT and DMM to verify 0 V AC at the internal power terminals—this confirms AC supply is removed.
  3. Step 3 – Recognize that a motor-start capacitor stores DC charge independently of the AC supply. The DMM AC voltage test does NOT indicate whether the capacitor holds a charge, because the stored charge may be DC.
  4. Step 4 – Set the DMM to DC volts at an appropriate range before touching any capacitor terminals. Measure across the capacitor terminals. If voltage is present, the capacitor must be discharged using a properly rated discharge resistor tool before any work continues near the capacitor.
  5. Step 5 – After discharge, re-measure across the capacitor terminals to confirm the voltage has dropped to a safe level (near 0 V DC).
  6. Step 6 – Only after both AC supply and stored capacitor charge are verified or discharged should work near those components proceed.
Answer: A zero AC voltage reading confirms the supply is isolated but does not address stored DC charge in the capacitor. The technician must also measure and discharge the capacitor, confirming near 0 V DC across its terminals, before the area is safe to work in.
4. You test a known-live 120 V outlet with your DMM before beginning a lockout and the meter reads 118 V AC. After completing lockout/tagout on the appliance, you probe the appliance's internal terminal block and the meter reads 0 V AC. Is this result reliable? Explain what the pre-test on the live outlet confirmed.
  1. Step 1 – The pre-test on the live outlet confirmed that the meter's test leads, fuse, battery, and circuitry are functional—the meter is capable of displaying a voltage when one is present.
  2. Step 2 – 118 V AC is within the normal range for a 120 V nominal circuit (voltage at residential outlets routinely measures between approximately 114 V and 126 V); the meter reading is expected and confirms the meter is working correctly.
  3. Step 3 – Because the meter proved functional on the live source immediately before the appliance test, a 0 V AC reading at the appliance terminal block is a reliable indication that no AC voltage is present at those points.
  4. Step 4 – This two-step verification (live source check → appliance check) is required practice. Skipping the live-source confirmation leaves open the possibility that a faulty meter could falsely read 0 V on an energized circuit.
Answer: Yes, the result is reliable. The pre-test on the live outlet confirmed the meter is functioning correctly. A reading of 118 V AC on a nominal 120 V circuit is normal. The subsequent 0 V AC reading at the appliance terminal block therefore accurately indicates de-energization.
In class: Instructor-led review of OSHA lockout/tagout requirements (OSHA 29 CFR 1910.147) using the program's safety reference guide; students annotate a printed checklist identifying energy sources—120 V AC, 240 V AC, stored capacitor charge, and gas ignition circuits—on three appliance types. · Hands-on station rotation: each student physically locks out a washer, a range, and a refrigerator using a personal lock and tag, then uses a non-contact voltage tester and a multimeter set to AC voltage to verify zero energy before signing a de-energization log. · Group case-study discussion of two documented appliance-related electrical accidents (sourced from CPSC and OSHA investigation summaries); students identify which safety step was skipped and rewrite the correct procedure in their own words.
Materials: OSHA 29 CFR 1910.147 summary card, non-contact voltage testers, digital multimeters (Fluke 117 or equivalent), personal lockout locks and tags, hasp devices, de-energization log forms, PPE (safety glasses, insulated gloves rated 1000 V), sample appliances (washer, range, refrigerator) disconnected from supply
Check: Student completes the lockout/tagout station checklist without prompting and verifies zero voltage at all test points on all three appliances; instructor marks pass if all six steps are performed in correct order with no skipped verification — 100% completion required, no partial credit.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Safety and Environmental Practices
1. Which OSHA standard specifically governs lockout/tagout procedures for the control of hazardous energy?
Safety and Environmental Practices
2. A technician unplugs a gas dryer and immediately begins working on the electronic igniter board. Which hazardous energy source has NOT been controlled?
Safety and Environmental Practices
3. After unplugging a microwave oven, a technician uses a non-contact voltage tester near the magnetron and gets no alarm. Is it safe to touch the high-voltage capacitor?
Electrical Theory and Diagnostics
4. During a lockout/tagout procedure on an electric range, a technician verifies 0 V AC between Line 1 and neutral, and between Line 2 and neutral, but skips the Line 1 to Line 2 measurement. What hazard remains unconfirmed?
Electrical Theory and Diagnostics
5. What is the correct DMM setting for measuring AC voltage on a 240 V appliance circuit when using a non-auto-ranging meter?
Safety and Environmental Practices
6. According to lockout/tagout best practice, who is permitted to remove a personal lock from a lockout point?
Safety and Environmental Practices
7. A technician is about to test for voltage at an appliance terminal block before confirming the lockout is complete. Which PPE is required at this point?
Safety and Environmental Practices
8. A case study shows a technician was injured while servicing a washing machine that had been 'turned off' but not unplugged or locked out. Which step in the six-step lockout/tagout procedure was most critically omitted?
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