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newSchoolWorks.com › VoTechWorks › Business & Cross-Cutting › Locksmith & Security Systems › Electronic Locks: Installation, Programming, and Servicing › Lesson 2
BUS-LOCK72-07 · Lesson 2 · 14 clock hours · lab

Wiring, Low-Voltage Electrical Safety, and Hardware Installation

Objective. Students will safely wire and mechanically install an electrified strike and a maglock on a practice door frame to manufacturer specifications, passing an instructor inspection checklist with no safety violations and no more than two correctable wiring errors.

⚠ 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.

Wiring, Low-Voltage Electrical Safety, and Hardware Installation

Why This Lesson Matters

Electrified strikes and maglocks are the mechanical heart of every access control system. A loose wire termination can cause intermittent failures that are almost impossible to diagnose remotely. An incorrectly wired maglock on an egress door can trap occupants during a fire. Getting the electrical and mechanical installation right the first time protects people, protects property, and protects your license.

Low-Voltage Electrical Hazards

Most access control hardware runs on 12 VDC or 24 VDC supplied by a dedicated power supply. "Low voltage" does not mean "no hazard." The real dangers are:

Rule for this lab: The power supply remains unplugged or switched off until the instructor approves your wiring. This is the low-voltage equivalent of lockout/tagout (LOTO).

Lockout/Tagout for Low-Voltage Work

OSHA's lockout/tagout standard (29 CFR 1910.147) applies whenever workers service or maintain equipment where unexpected energization could cause injury. For low-voltage access control:

1. Identify the energy source (the DC power supply).

2. Disconnect and, where possible, lock or tag it out before making or changing terminations.

3. Verify the circuit is de-energized with a digital multimeter before touching bare conductors.

4. Re-energize only after all tools are clear and all persons are aware.

In this lab the instructor acts as the authorized person who verifies de-energized status before you connect wires and who authorizes re-energization after inspection.

PPE Selection

Reading a Manufacturer Wiring Diagram

Every electrified strike and maglock ships with an installation manual that includes a wiring diagram. Before picking up a tool, locate:

Installing an Electrified Strike

An electrified strike replaces a conventional door strike in the frame. In fail-secure mode, power is required to unlock it — the door stays locked if power fails, which is appropriate for secure-area doors that are not primary egress.

Mechanical installation steps:

1. Remove the existing or placeholder strike; verify the mortise cutout dimensions match the electrified strike body.

2. Route 18/2 wire from the power supply location through the frame to the strike location before mounting; dress wire so it cannot be pinched by the frame hardware.

3. Seat the strike body flush, fasten with the supplied screws to manufacturer torque guidance.

Wiring steps:

1. Strip approximately 1/4 inch of insulation from each conductor — no more, to minimize exposed bare wire at the terminal.

2. Connect the positive (usually red) conductor to the + terminal and the negative (usually black) conductor to the COM or − terminal.

3. Tighten terminal screws firmly; tug each wire gently to confirm it does not pull free.

4. Connect the door position switch in series with the control circuit per the wiring diagram so that the panel knows whether the door is open or closed.

Installing a Maglock

A maglock (electromagnetic lock) holds a door closed by magnetic attraction between the lock body mounted on the frame and an armature plate mounted on the door. In fail-safe mode, power is required to lock it — the door releases if power fails. Fire code requires fail-safe operation on emergency egress doors so occupants can exit during a power outage or fire alarm event.

Mechanical installation:

1. Use the manufacturer's drilling template to locate anchor points on the frame header and on the door face. Accuracy here is critical — misalignment reduces holding force significantly.

2. Drill anchor holes with the correct bit diameter for the supplied hardware.

3. Mount the maglock body to the frame header; mount the armature plate to the door, leaving the adjustment screws slightly loose.

4. Close the door and allow the maglock to pull the armature plate into full-face contact before tightening armature plate screws. Full-face contact is essential to achieve rated holding force.

Wiring steps:

1. Route 18/2 wire from the power supply through the frame; use a frame raceway or door loop for the door-side run if needed.

2. Connect wires per polarity markings on the maglock.

3. Wire the push-button REX (request-to-exit) device in parallel with the control input so that pressing the button interrupts power to the maglock and releases the door.

4. Route and dress all wire neatly; secure with cable staples at intervals consistent with the manufacturer's guidance — never staple through the wire.

Verifying the Installation

Once the instructor approves the wiring, restore power and test:

Record any measured deviations and correct them before signing off.

Key terms9

Fail-secureA lock mode in which the device remains locked when electrical power is removed; used on secure-area doors that are not required egress paths.
Fail-safeA lock mode in which the device releases (unlocks) when electrical power is removed; required by fire code on emergency egress doors so occupants can exit during a power failure or fire alarm.
Electrified strikeA door strike mounted in the frame that uses electric current to retract or hold the keeper, allowing a credential reader to control access without modifying the door-mounted hardware.
Maglock (electromagnetic lock)An access control device that uses the attractive force between an electromagnet body and a steel armature plate to hold a door closed; holding force is rated in pounds and must be verified at installation.
REX (request-to-exit) deviceA sensor or push button that signals the access control system that a person inside intends to exit, triggering lock release without requiring a credential from that side.
Lockout/tagout (LOTO)An OSHA-required safety procedure (29 CFR 1910.147) that isolates energy sources — including electrical power supplies — and verifies de-energization before workers make connections or repairs.
18 AWG two-conductor wire (18/2)The wire gauge and configuration commonly used for short access control runs; AWG (American Wire Gauge) numbers decrease as wire diameter increases, so 18 AWG is thicker and lower-resistance than, for example, 22 AWG.
Door position switch (DPS)A magnetic contact sensor mounted on a door and frame that signals the access control panel whether the door is open or closed, enabling alarm and audit functions.
Armature plateThe steel plate mounted on the door face that contacts the maglock body; full-face contact between armature and maglock is required to achieve the device's rated holding force.

Worked examples4

1. A maglock datasheet lists a current draw of 0.5 A at 12 VDC. The technician plans a wire run of 40 feet (one-way) using 18 AWG copper wire, which has a resistance of approximately 6.4 ohms per 1,000 feet. What is the total wire resistance for the round-trip run, and what is the resulting voltage drop across the wire?
  1. Calculate the total wire length for the round trip: 40 ft (positive run) + 40 ft (return run) = 80 ft total.
  2. Calculate total wire resistance: (80 ft ÷ 1,000 ft) × 6.4 Ω = 0.08 × 6.4 = 0.512 Ω.
  3. Apply Ohm's Law to find voltage drop: V = I × R = 0.5 A × 0.512 Ω = 0.256 V.
  4. Compare to supply voltage: 0.256 V drop on a 12 V supply is about 2.1%, well within the typical 10% maximum tolerance listed in most installation manuals, so 18 AWG is acceptable for this run.
Answer: Total round-trip resistance ≈ 0.51 Ω; voltage drop ≈ 0.26 V, which is acceptable for a 12 VDC maglock on this run length.
2. A maglock is rated at 1,200 lb holding force. During the pull-off test, the technician notices the door releases with noticeably less effort than expected. The armature plate mounting screws were tightened while the door was open. What is the likely cause and correction?
  1. Identify the installation step: armature plate screws were tightened with the door open, meaning the armature was not pulled into full-face contact with the maglock body when fastened.
  2. Diagnose the result: a gap or misalignment between armature plate and maglock body reduces the magnetic flux path, dropping holding force well below the rated value.
  3. State the correction: loosen the armature plate screws, energize the maglock to pull the armature into full contact with the lock body, then tighten the screws with the door closed and the maglock energized.
  4. Verify the fix: attempt the pull-off test again; resistance should be consistent with the rated holding force.
Answer: The cause is armature plate misalignment due to tightening screws with the door open. The correction is to re-set the armature with the maglock energized and door closed before final tightening.
3. A technician strips 3/4 inch of insulation from each conductor before inserting them into a terminal block designed for 1/4-inch strip length. What are two risks created by the excess bare conductor?
  1. Identify the first risk: excess bare wire extending beyond the terminal clamp can contact an adjacent terminal, causing a short circuit that may damage the power supply or the lock controller.
  2. Identify the second risk: bare wire extending outside the terminal housing is exposed to incidental contact — by tools, by a building occupant, or by a metal frame surface — creating a shock or short-circuit hazard and a code violation.
  3. State the correct action: re-strip conductors to approximately 1/4 inch (or to the strip-length gauge marked on the device), re-terminate, and confirm no bare copper is visible outside the terminal clamp.
Answer: Excess bare conductor risks: (1) short circuit to an adjacent terminal, and (2) incidental contact with tools or conductive surfaces. Re-strip to the manufacturer's specified strip length.
4. A technician measures 0 VDC across a maglock terminal block after energizing the power supply. The supply output measures 12 VDC at its own terminals. What is a logical diagnostic sequence using a digital multimeter?
  1. Step 1 — Check the wire run from supply to lock: place meter probes at the far end of the positive and negative conductors (before they enter the terminal block) and measure voltage. If 12 VDC is present here, the wire run is intact.
  2. Step 2 — If voltage is present at the wire ends but not at the terminals, suspect a loose or missed termination; re-seat and re-tighten both conductors in the terminal block.
  3. Step 3 — If voltage is absent at the wire ends, use the meter in continuity mode (power off, LOTO applied) to trace the break — probe from supply terminal to lock terminal on each conductor separately to find which conductor is open.
  4. Step 4 — Once the fault is located and repaired, de-energize, reconnect, re-energize, and re-measure at the lock terminals to confirm 12 VDC is present before testing lock operation.
Answer: Systematically trace voltage from supply to lock terminals using a multimeter; a missing voltage at a mid-point isolates the fault to that segment, directing the repair.

The math in this lesson2

Learners express a 0.256 V drop as about 2.1% of a 12 V supply.
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Brush up in the math halls at newSchoolWorks.com:
In class: Safety briefing (mandatory before tool use): instructor reviews low-voltage electrical hazards, OSHA lockout/tagout requirements for working on powered circuits, PPE selection (safety glasses, insulated hand tools), and fire code considerations for fail-safe maglocks on egress doors; students sign a safety acknowledgment form. · Hands-on wiring lab in pairs: students read a manufacturer wiring diagram, strip and terminate 18 AWG two-conductor wire at an electrified strike and at a door position switch, connect to a practice access control power supply, and verify operation by presenting a credential; instructor circulates and flags incorrect polarity or loose terminations before energizing. · Maglock installation exercise on a steel practice door frame: students locate and drill anchor points, mount the maglock body and armature plate, route and dress wire through the door frame, connect to a power supply with a pushbutton REX, and test holding force by attempting manual pull-off; measured holding force is compared to the rated specification on the datasheet.
Materials: Practice door frame stations (one per pair), fail-secure electrified strike, fail-safe maglock with armature plate, 18 AWG two-conductor wire, wire strippers, insulated screwdrivers, cordless drill and bits, fish tape, cable staples, door position switches, push-button REX devices, DC power supplies, digital multimeters, manufacturer installation manuals, instructor wiring inspection checklist, safety glasses (provided), OSHA low-voltage electrical safety reference
Check: Instructor completes a 15-point installation inspection checklist for each pair's finished work: zero safety violations (immediate fail and re-do required), wire terminations secure with correct polarity, lock operates on credential presentation, REX releases lock, door position switch signals correctly. Maximum two correctable wiring errors permitted before sign-off.

Practice check8

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

Electronic security systems — access control and life safety
1. A fail-safe maglock is required on an emergency egress door primarily because:
Occupational safety — lockout/tagout
2. Before re-terminating wires on a powered access control power supply in a commercial installation, the technician's first action should be to:
Electronic security systems — electrified hardware installation
3. After mounting an armature plate, a technician tests the maglock and finds holding force is well below the rated value. The most likely cause is:
Occupational safety — electrical hazards
4. Which wiring error poses the greatest immediate fire risk when an access control power supply is energized?
Electronic security systems — access control wiring
5. A REX (request-to-exit) push button should be wired in __________ with the maglock control circuit so that pressing it releases the door.
Electronic security systems — installation practices
6. When stripping conductors for termination in a terminal block, the correct strip length is generally:
Electronic security systems — troubleshooting
7. A digital multimeter set to DC voltage reads 0 V at a maglock terminal block, but 12 V at the power supply output terminals. The most logical next diagnostic step is to:
Electronic security systems — access control components
8. On an access control wiring diagram, the terminal labeled 'NO' on a door position switch refers to:
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