Written by Steven G., licensed NYC locksmith (DCWP License #2065742-DCA), Golden Key Locksmith, 328 Columbus Ave, Manhattan. We install and wire electric strikes across NYC offices, storefronts, and apartment buildings.
An electric strike circuit has three parts: a power supply (transformer or regulated supply), a switch (a button, keypad, intercom relay, or access-control panel), and the strike itself. Power flows from the supply, through the switch’s relay contact, to the strike — and when the switch closes, the strike’s keeper releases and the door opens. Everything else in this guide is about getting three decisions right before you connect those wires: voltage, AC vs DC, and fail-safe vs fail-secure.
The basic wiring diagram
The standard single-door circuit, in words:
- Power supply positive (+) runs to one terminal of your switching device — the relay output on an access panel, intercom amplifier, or a simple normally-open (NO) push button.
- From the switch’s other terminal, the wire continues to the strike’s first terminal.
- The strike’s second terminal returns to the power supply negative (−), completing the loop.
That’s the whole circuit: supply → switch → strike → back to supply. Press the button, the contact closes, current energizes the strike’s solenoid, the keeper releases. On an access-control panel, the panel’s relay plays the role of the button.
One component beginners skip and regret: on a DC strike, fit the small suppression diode (typically a 1N4004, included in the box) across the strike terminals, stripe toward positive. Without it, the voltage spike each time the strike releases will eventually damage your access panel’s relay. On AC strikes, use the supplied MOV instead.
Decision 1: Voltage — 12V or 24V
Match the strike, the power supply, and the controller. Most small installations run 12V DC; larger commercial systems and longer cable runs favor 24V because it tolerates voltage drop better. Check the strike’s label — many modern strikes accept both via a jumper or dual coils. Never guess: a 24V supply on a 12V-only strike burns the solenoid.
Decision 2: AC or DC
- AC gives the classic buzz when the door releases — useful as an audible cue on street doors and intercom entries.
- DC releases silently, runs cooler, and is required for strikes held powered for long periods and for battery-backup systems.
Intercom buzzer systems in NYC apartment buildings are traditionally AC; modern access-control installs are almost always DC. Your controller’s output must match.
Decision 3: Fail-safe or fail-secure (the one that involves the law)
- Fail-secure (standard): the strike stays locked when power is cut. The door still opens freely from inside with the handle. Right choice for most entries — burglars can’t get in by cutting power.
- Fail-safe: the strike unlocks when power is cut. Required where a locked door in a power failure would trap people or block emergency access — stairwell re-entry doors and certain egress paths in commercial buildings.
In NYC this is not a style preference: egress and re-entry requirements in the Building Code and FDNY rules dictate which mode specific doors must use, and fire-rated door assemblies must keep their rating after the strike is cut into the frame. Wiring the strike is the easy half; specifying it legally on the right door is where commercial jobs go wrong.
Wire gauge and run length
Thin wire over a long run starves the strike. As a working rule: 18 AWG covers typical runs to roughly 50 feet at 12V; go one size heavier (16 AWG) for longer runs or 24V systems with multiple devices; intercom-style low-current buzzers tolerate more. If a strike buzzes weakly or releases intermittently at the end of a long run, measure voltage at the strike under load — voltage drop is the usual culprit.
Wiring into an access-control system
On the panel, the strike wires to the relay output: common (COM) and normally-open (NO) for fail-secure, or common and normally-closed (NC) for fail-safe, so the panel’s “unlock” action does the correct thing in each mode. Keep the strike on its own fused supply output — sharing one unfused output between readers, panel, and strike is the most common cause of controllers rebooting each time the door releases. If the system includes a request-to-exit device or door position sensor, those wire to the panel’s inputs, not into the strike circuit.
Troubleshooting quick table
- Nothing happens: check voltage at the strike terminals while the switch is held. No voltage = supply/switch problem; correct voltage = strike or alignment problem.
- Buzzes but doesn’t release: keeper is binding against the latch — the door is pre-loaded. Realign the strike pocket or adjust the door so the latch isn’t pressing into the keeper.
- Releases intermittently: voltage drop on a long run, or a failing supply under load.
- Panel resets when door releases: missing suppression diode, or strike sharing the panel’s power output.
When to call a pro
DIY is reasonable for a single interior door on a plug-in supply. Call a licensed pro when the door is fire-rated (nearly all apartment-building entry and stairwell doors in NYC), when the strike ties into an intercom or building-wide access system, or when the door is on an egress path — the fail-safe/fail-secure specification carries legal weight there. We wire strikes into access control systems across the city, handle the code side, and quote a flat price before work begins. Golden Key Locksmith — DCWP #2065742-DCA, at 328 Columbus Ave since 1984. (212) 204-1655.
Frequently asked questions
What power supply does an electric strike need?
A supply matching the strike’s voltage and type (12V or 24V, AC or DC) with enough current for the strike’s rating — typically a fraction of an amp per strike. For access-control systems, use a fused, regulated DC supply with battery backup rather than a bare transformer.
Can I wire an electric strike to my apartment intercom?
Usually yes — the intercom’s door-release button already switches a strike circuit; a compatible strike replaces the old one on the same pair. In multifamily buildings the intercom and entry door are typically building property, so this is a job for building management and their installer, not an individual tenant.
Does an electric strike still let people out in a power failure?
Yes, in both modes. The strike only controls the outside of the door; the inside handle always retracts the latch mechanically. Fail-safe vs fail-secure decides whether the outside is locked or unlocked when power is lost.
Fail-safe or fail-secure — which do I want?
Fail-secure for almost every entry door: power cut = still locked from outside. Fail-safe only where code requires the door to release on power loss, such as stairwell re-entry doors. On NYC commercial jobs this is dictated by egress code, not preference.
Why does my electric strike buzz but not open?
The door is pressing its latch into the strike’s keeper, so the keeper can’t pivot. Have someone push the door slightly closed while releasing — if it opens, realign the strike or adjust the door closer so the door isn’t pre-loading the latch.
