How to Wire an Electric Strike

The strike is in the frame and the controller is on the wall; now the two have to meet. Knowing how to wire an electric strike comes down to four decisions: the right power supply, the right relay contact, the right suppression, and a test of every door state before handover. This guide works through them in the order you would on site.

Read the strike and controller sheets first

Every wiring decision comes from two data sheets. Before pulling cable, note from the strike sheet:

• Voltage and type: 12 or 24 V, AC or DC. Many strikes are field-selectable.
• Current draw at that voltage, in amps or milliamps.
• Duty rating: continuous duty if the door will be held unlocked on a schedule. Some AC strikes are rated only for brief pulses.
• Fail mode: fail-secure or fail-safe, and whether it is set by a jumper or screw.
• Suppression: whether a diode or varistor is supplied or required.

From the controller sheet, note the lock relay’s contact rating and whether the output is a dry contact or supplies voltage itself. A University of Nevada, Las Vegas physics handout on relay basics puts the rule simply: choose contacts that can handle the voltage and current of the load. If the strike exceeds the rating, an interposing relay goes between them.

Sizing the electric strike power supply

Use a dedicated, regulated supply whose voltage and type (AC or DC) match the strike, rather than borrowing power from the controller’s auxiliary terminals. The fail mode changes the duty: a National Institutes of Health technical bulletin on fail safe vs fail secure locksets notes that fail-secure hardware draws power only to unlock, while fail-safe hardware draws it continuously.

Size it by adding every load on the output. As a worked example, assume a 12 VDC strike drawing 0.45 A and a reader on the same supply drawing 0.15 A; both are assumed figures, so use your own data sheets:

• Total load: 0.45 + 0.15 = 0.60 A.
• With 25 percent headroom, an installer’s margin rather than a standard: 0.60 x 1.25 = 0.75 A.
• Choose a supply whose rated continuous output is above that figure.

Add battery backup if card access must keep working through an outage. A fail-secure strike stays locked without power, so the backup keeps users getting in, not the door closed.

AC vs DC strikes and the suppression diode

An AC strike hums or buzzes while energized. A DC strike is quiet, which most owners prefer on offices. When a DC coil switches off, the energy stored in its magnetic field has to go somewhere. The UNLV handout notes that the resulting spike can reach hundreds or thousands of volts, and that kickback from a DC inductive load shortens relay contact life.

A diode across the coil gives that energy a path. Fit it at the strike, banded end (cathode) to positive and the other end to negative, so it carries no current in normal operation. Use the part and polarity in the strike instructions; some makers specify a varistor instead or as well.

Never put a diode across an AC strike. It conducts on every other half cycle and shorts the supply.

Electric strike wiring diagram, step by step

The common pattern switches the positive leg through the controller’s dry lock relay:

1. Supply positive to the relay’s common (COM) terminal.
2. Relay normally open (NO) for fail-secure, or normally closed (NC) for fail-safe, to the strike’s positive lead.
3. Strike negative back to supply negative.
4. Suppression device across the strike leads, at the strike.

If the controller’s lock output supplies voltage itself, follow its own diagram instead. Make every connection with the supply and battery disconnected.

Which fail mode a door should have is a separate decision, covered in maglock vs electric strike. Either way, the inside lever or panic bar still opens the door mechanically.

Cable size and voltage drop

Long runs lose voltage, and a strike that receives too little may hum without releasing. Measure the one-way run, double it for the loop, and multiply by the copper resistance; the table in our speaker wire gauge guide gives 6.385 ohms per 1,000 ft for 18 AWG.

• 100 ft one way is a 200 ft loop: 200 x 6.385 / 1,000 = 1.28 ohms.
• At the assumed 0.45 A: 1.28 x 0.45 = 0.57 V, or 4.8 percent of 12 V.
• A 24 V strike of similar power draws about half the current: 0.29 V, or 1.2 percent of 24 V.

Check the result against the voltage tolerance on the strike sheet, step up a gauge or move to 24 V if it is tight, and measure at the strike while it is energized.

Fit the strike to the latch and keeper

Wiring cannot fix a strike that does not suit the door. The strike must match the lockset’s latch type and the frame, and its keeper has to line up with the latch both across and up and down.

• With the door closed, check that the latch sits in the keeper without pressing on it. Preload from weatherstrip or a warped door can stop a keeper releasing.
• Check that the latch’s deadlocking plunger rests where the lock and strike instructions show, so the latch stays deadlocked.
• Close the door slowly and briskly to confirm it latches every time.

Door contact, REX and fire alarm by reference

A strike door normally also has a door position switch and a request-to-exit input. Wire the switch to the controller’s contact input, and the REX as set out in our request to exit sensor guide.

Fire-rated doors are stricter. The NIH bulletin states that electric strikes on fire-rated doors must be fail-secure, per NFPA 80, and that fail-secure is typical unless a fire alarm must release access. Any fire alarm interface follows the design, and the authority having jurisdiction decides.

Testing and handover

Test every state before handover, and leave an as-installed wiring diagram with the owner. A practical sequence:

1. Present a valid credential: the strike releases and relocks on the set time.
2. Present an invalid credential: nothing releases.
3. Exit from inside: the REX shunts the alarm and no forced-door event is logged.
4. Prop the door: the held-open alarm reports.
5. Remove mains, then battery: the strike goes to its stated fail mode.
6. Trip the fire alarm input where fitted: the door does what the design says.

For larger sites, standalone vs networked access control covers the controller side.

Where to find access control products

The access control category lists access control products, and the security wire and cable category lists cable, both in the Security, Surveillance and Control division. For pricing and availability, ask your sales representative through the Bursma contact page, or open a Bursma dealer account.

Frequently asked questions