When contractors begin electrifying a door, most of the attention goes to the lock, strike, or panic hardware. But none of it works properly without the correct power supply. The power supply is the foundation of every access control opening. If it is undersized, unregulated, or improperly specified, you will see intermittent failures, premature hardware wear, and expensive service calls.
Before selecting a power supply, you must confirm voltage requirements. Most commercial access control hardware operates on 12VDC or 24VDC. Some devices are field selectable, while others are voltage specific. Running incorrect voltage can damage components or reduce holding force in devices such as magnetic locks or solenoid driven exit hardware.
Next, calculate total amperage draw. Add the current requirements of each device connected to the opening, including electrified mortise locks, latch retraction kits, electric strikes, REX devices, card readers, and door position switches. Always allow additional capacity for inrush current. Under sizing the power supply leads to voltage drop and inconsistent operation.
Battery Backup and Fire Alarm Integration
Another major consideration is battery backup. Many commercial installations require continued operation during power loss. A properly listed access control power supply enclosure typically includes space for sealed lead acid batteries to maintain uninterrupted output.
For example, the PS220B from Command Access delivers 2 amps at 24VDC and supports two 12V 7AH batteries for automatic switchover during power failure. This ensures electrified locks, solenoid exit devices, and latch retraction hardware continue operating when building power is interrupted.
Fire alarm integration is equally critical. In fail safe applications such as maglocks, the power supply must drop power when the fire alarm activates. The PS220B includes fire alarm link compatibility, allowing the system to release power appropriately during emergency conditions. This is essential for maintaining life safety compliance.
Centralized vs Distributed Power
Finally, determine whether the project calls for centralized or distributed power. Centralized panels are common in schools and larger facilities where multiple openings are managed from a single enclosure. Smaller projects may benefit from localized supplies closer to the door to reduce voltage drop.
Choosing the correct power supply is not optional. It is the backbone of a reliable, code compliant access control system. Electrified hardware gets the attention, but the power supply determines whether the opening performs consistently year after year.