Overview
To maintain full system operation during a power outage, all components in the access control chain must have backup power — not just the intercom and controllers.
Components That Must Be on UPS
The following devices should each be connected to a UPS:
- ButterflyMX intercom
- Door controller(s)
- PoE switch or injector (if applicable)
- Router, firewall, and ISP modem/ONT
⚠️ Without network equipment on UPS, the intercom may stay powered but lose cloud connectivity, preventing mobile app calls and remote unlock.
Door Strikes & Maglocks
The door controller sends the unlock signal, but locking hardware depends on its own power source. If that power source is not backed up, the controller will function but doors will not respond to unlock commands.
- Electric strikes are typically fail-secure — they remain locked when power is lost
- Maglocks are typically fail-safe — they release when power is lost
If strikes or maglocks are powered by a dedicated 12/24VDC power supply, that supply must also be on UPS or replaced with a battery-backed access control power supply.
Exception — Wet Relay on a 2-Door Controller
If a 2-door controller is powering the lock directly via its wet relay output, the lock draws power from the controller itself. Placing the controller on UPS covers the lock as well.
⚠️ Always verify wiring on-site to confirm this configuration before assuming the lock is backed up.
UL 294 Battery Backup — Optional
The 2-door controller supports an optional 12VDC 9Ah lead acid battery connected directly to the controller's battery backup input. This is only required for buildings that need UL 294 compliance and is separate from the UPS on the primary AC power supply.
Minimum UPS Sizing Guidance
UPS sizing should be based on the power source or power group, not every individual endpoint. In most deployments, readers, keypads, vehicle readers, and other downstream accessories are already covered by the controller power supply or the PoE switch powering them.
| Power Group | Typical Covered Devices | Minimum Recommended UPS |
|---|---|---|
| Intercom power | 8" and 12" intercoms (surface and recessed) | 600VA / 300W |
| Controller power | 2-door controller, connected readers, wet relay locks if powered from controller | 100VA / 60W per controller power supply |
| Camera gateway | Camera gateway | 25VA / 15W |
| Small PoE camera setup | Up to 5 cameras or similar low-draw PoE devices | 150VA / 80W |
| Larger PoE camera setup | Up to 10 cameras or similar higher-draw PoE devices | 250VA / 150W |
| Network equipment | Router, modem, firewall, small switch | 350VA / 200W baseline |
| Dedicated lock power | Separate 12/24VDC strike or maglock supply | Size to actual lock load + 25% headroom |
Additional notes:
- Readers powered from the controller do not need their own separate UPS
- PoE devices should be sized based on the PoE switch or injector total load, not per endpoint (unless dedicated injectors are used)
- If a lock is powered by a dedicated power supply, that supply must be backed up separately
- If a lock is powered from the 2-door controller wet relay, the controller UPS covers it — verify wiring on-site
Universal Sizing Rule
Add the total wattage of all devices sharing the same UPS, then select a unit rated at least 20–25% above that load to allow for startup variation, battery aging, and future expansion.
ℹ️ These recommendations are intended as minimum baseline sizing guidance. Actual UPS sizing should be based on the full connected load and the desired battery runtime.