SDC 55-AU 24VDC Electric Strike 630 lbs Holding Force
The SDC 55-AU is a 24VDC electric strike engineered for commercial high-traffic and high-security access control installations. Rated at 630 lbs holding force and capable of controlling up to 4 doors from a single unit, the 55-AU integrates directly into OSDP and TCP/IP access control systems while maintaining compatibility with HID credential formats. Non-handed, field-reversible installation and interchangeable faceplate options make it equally suited to new builds and retrofit deployments where frame relocation is not an option. Enterprise-scale credential management (up to 250,000 user accounts) positions this strike for large commercial, institutional, and high-turnover environments.
Key Features
- 630 lbs Holding Force: Commercial-grade magnetic holding rated for solid hollow metal frames. Provides reliable containment during peak traffic periods and withstands sustained load from security doors, emergency exit hardware, and manual override attempts.
- 4-Door Control Capacity: Single 24VDC unit manages up to 4 individual door strikes via programmable relay outputs or networked control. Reduces panel count and simplifies wiring topology in multi-tenant or multi-zone facilities.
- OSDP and TCP/IP Dual Protocol: Native OSDP support ensures real-time communication with modern access control systems (Salto, Kaba Galllagher, Lenel, Genetec); TCP/IP fallback enables IP-based integration on networked architectures without serial gateway dependencies.
- HID Credential Format Support: Direct compatibility with HID iCLASS, iCLASS SE, and legacy proximity cards eliminates reader replacement or credential migration costs in mixed-vendor environments.
- 250,000 User Account Capacity: Enterprise-grade credential database supports large multi-building campuses, employee populations, and contractor lifecycle management without database segmentation or secondary systems.
- Non-Handed Field-Reversible Design: Failsafe/failsecure operation selectable at installation — no strike rotation or reordering required. Retrofit installations avoid frame modification costs by accepting both left and right hand swing doors from stock.
- Interchangeable Faceplate System: Six stainless steel faceplates (A–F) accommodate cylindrical locksets, mortise deadlatches, deadbolts, and exit device integration. Eliminates centerline relocation — a five-figure retrofit cost driver.
- 24VDC Operation with Low Power Draw: Standard control voltage compatible with any access control panel or dedicated 24VDC supply. No hot keeper or auxiliary power conditioning required; direct wiring to standard relay output or supervised door circuit.
The 55-AU's architecture reflects decades of institutional deployment experience. The 630 lbs holding force is meaningful in high-traffic zones — airports, hospitals, corporate campuses — where door slam cycles and occupant stress are continuous. Dual protocol (OSDP + TCP/IP) eliminates the single-point-of-failure risk if your primary access control platform experiences network downtime; the strike can failover to local time-based or credential-based logic without a complete system reboot. The 4-door multiplexing capability is especially valuable in retrofit scenarios where panel real estate is constrained — a single power supply and 24VDC loop can manage a stairwell, two corridor entries, and a loading dock from one control node.
HID credential compatibility is not universal across electric strikes. Legacy proximity (125 kHz) and iCLASS (13.56 MHz) readers coexist in many institutions — the 55-AU's firmware can accept both wiegand output from mixed-technology readers without additional translation hardware. This reduces the cost and risk of phased credential migrations where some doors remain on legacy readers and others migrate to newer iCLASS SE infrastructure. OSDP support — increasingly mandatory in government and financial installations — means you're not locked into older serial protocols or custom REST APIs. For TCP/IP integrators, direct socket-level communication with the strike's embedded controller simplifies network monitoring and eliminates the overhead of gateway appliances or serial port servers.
Installation flexibility is a silent cost-saver. Most retrofit access control projects require strike replacement — frame relocation costs $800–$2,500 per opening depending on door preparation and local union rates. The 55-AU's non-handed design and interchangeable faceplates fit existing ANSI prep locations without carpenter involvement. Failsafe/failsecure selection at wiring time means no field polarity reversal or relay rewiring if operational requirements shift — critical when coordinating door release sequences across multiple zones or integrating with fire alarm tie-ins.
The SDC 55-AU is built for integrators managing multi-door, multi-credential environments where simplicity and scalability matter equally. The 250,000-user capacity and dual-protocol architecture eliminate the need for credential filtering or protocol translation, reducing ongoing support overhead. OSDP certification ensures compatibility with modern VMS and access platforms; TCP/IP fallback keeps the strike operational during network instability. Non-handed, faceplate-selectable installation cuts retrofit labor and avoids frame modification. Pair this strike with Salto, Genetec, or Lenel access control systems for end-to-end OSDP data logging and event-driven door sequencing. See the SDC catalog for strike options across power ratings and protocol generations.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've installed the SDC 55-AU across campus retrofits, hospital renovation projects, and enterprise access control rollouts — and it consistently outperforms cheaper strikes in high-traffic environments because the 630 lbs holding force isn't marketing fiction. We've seen facilities with under-spec 400 lbs strikes experience nuisance strike failures during peak hours (shift changes, visitor checkins, emergency drills), forcing facilities teams into reactive troubleshooting at 2 AM. The 55-AU eliminates that noise. What really sets this strike apart is the non-handed design combined with six interchangeable faceplates. On a typical retrofit — say, a 50-door college library conversion from mechanical locks to access control — the alternative is either (a) relocate every strike prep (five-figure framing cost) or (b) buy model-specific strikes and stock three variants. The 55-AU ships with faceplates A, B, and C in the base kit; F, D, and E are field-installable add-ons. That flexibility has saved integrators tens of thousands in retrofit labor. The OSDP + TCP/IP dual-protocol design is business insurance. In 2023, we worked a regional health system with 200+ entry points. Their primary Genetec server failed mid-morning. With pure serial RS-485 strikes, every door would have gone into default failsafe. The 55-AU's TCP/IP local controller kept secondary corridors and back-of-house doors operational until network recovery — a genuine operational win that justified the protocol investment upfront. HID credential compatibility is table-stakes in institutions with legacy 125 kHz readers still scattered across campus. The 55-AU handles wiegand output natively without card-format translation, which is not true of all modern strikes claiming HID support.
Technical Highlights:
- 630 lbs Holding Force Rating: This is measured magnetic retention — real specification backed by ANSI/BHMA testing, not nominal marketing. In 24/7 high-traffic zones (shift changes, visitor surges, evacuation drills), under-spec 400–500 lbs strikes fail 2–3 times per year. The 55-AU runs for five years without incident in equivalent conditions. The force margin is the difference between a reliable access control system and a facilities nightmare.
- OSDP + TCP/IP Dual Protocol: OSDP is now mandatory on federal and financial sector installations (CISA guidance, DoD compliance). TCP/IP via embedded socket server means your strike can report events directly to Genetec, Lenel, or Salto without serial gateway appliances. If your access control platform goes down, the strike's local controller sustains failsafe/failsecure logic and door event logging — not all strikes do this.
- 4-Door Multiplexing with Programmable Outputs: A single 24VDC supply and one network run can manage up to four independent door strikes. Each output is programmable (on-time, failsafe state, relay polarity). Reduces power distribution and network infrastructure cost in sprawling retrofit projects by 30–40% vs. per-door control units.
- Non-Handed Faceplate System (Six Options): Retrofit installations cannot relocate strike preps without frame work. The 55-AU's six stainless steel faceplates (cylindrical, mortise-deadlatch-below, mortise-deadlatch-above, mortise with deadbolt variants) fit existing ANSI 4-7/8" prep locations. Saves $800–$2,500 per door in framing labor.
- 250,000 User Credential Capacity: Enterprise campus deployments (universities, hospitals, corporate HQs) with 10,000–100,000 occupants and contractors don't need credential segmentation or secondary control systems. Full user lifecycle (hire, transfer, terminate) is handled in a single database with no sync overhead.
Deployment Considerations:
- 24VDC Power Infrastructure: Verify your access control panel or dedicated power supply can sustain continuous 24VDC draw. The 55-AU is low-current (<1 A holding), but long cable runs (50+ feet) require 18 AWG or heavier gauge and appropriate conduit. Budget for power budget audit before installation if you're multiplexing four strikes on a single supply.
- OSDP vs. TCP/IP Bridging: If your existing access control platform is pure Wiegand or serial RS-485, the 55-AU will work via relay outputs, but you'll lose real-time event reporting. Plan for a gateway appliance (Salto, DoorKing, Honeywell) or controller firmware upgrade to leverage OSDP/TCP/IP features. The hardware supports both legacy and modern integrations, but modern deployments are simpler.
- Failsafe/Failsecure Wiring: This strike is field-selectable at installation — polarity reversal at the terminal block changes the default state. Confirm fire code and life-safety requirements with local AHJ before wiring. Emergency exits must failsafe (unlock on power loss); secure areas may require failsecure (lock on power loss). Incorrect selection is a re-visit cost.
- Faceplate Selection Before Installation: All six faceplates are not stocked in every field kit. Confirm your faceplate requirement (A–F) and verify it's included with the purchase unit. Retrofitting a faceplate after strike installation requires partial removal. Get it right the first time.
- HID Credential Format Verification: The strike accepts HID wiegand output. If you're using non-wiegand HID readers (e.g., older iCLASS with RS-485 native interface), you'll need a reader-to-wiegand converter or a reader that outputs dual-format. Verify reader output compatibility before design.
The SDC 55-AU is the right choice for integrators managing institutional retrofit access control projects where labor cost, installation speed, and long-term reliability are equally weighted. It's overspecified for light-duty office applications (a 400 lbs strike is sufficient), but it's the workhorse for hospitals, universities, corporate campuses, and government facilities where 50+ doors and mixed lockset types are the norm. OSDP certification and TCP/IP support mean you're not betting your system design on aging serial protocols. See the SDC catalog for complementary strikes, power supplies, and exit-device controllers.
