What size (amp output) rack power supply do I need?
Calculate total continuous current: sum camera PoE draw (typical 5–15W each, or 0.2–0.6A at 24V), plus access control (locks 0.5–1A each, readers 0.2A each), plus any IR or lighting. Add 30–40% safety margin for startup surge and future expansion. A 8-camera + 4-lock system typically needs 30–50W (1.25–2A at 24V); verify your specific equipment datasheets before ordering.
Do I need a supervised output if my cameras are on PoE switches?
Yes. Supervised outputs detect wiring faults, power-distribution failures, and battery discharge—issues that PoE monitoring alone cannot catch. Your PoE switch may report that connected cameras are alive, but a failed internal supply relay or severed output cable will drop power before the NVR ever detects it. Supervision bridges that gap with independent volt-free contacts wired to your access control panel or NVR alarm input.
Can I connect multiple supplies in parallel for redundancy?
Typical rack supplies are not designed for safe parallel operation without additional diode isolation or load-sharing modules. Risk of backfeeding, unequal current distribution, and battery conflicts is high. Instead, use two independent supplies powering separate output banks (e.g., cameras on Supply A, locks on Supply B) or install a dual-supply UPS unit from the vendor. Consult Altronix or your distributor for redundancy guidance specific to your model.
How long will a 5Ah battery back up my system?
Hold-up time = (Battery Ah × Voltage) ÷ Load Current. A 5Ah 24V battery = 120 Wh ÷ 40W load = 3 hours theoretical; however, batteries cannot safely discharge below 50%, so practical hold-up is ~1.5 hours. For incident recovery, expect 3–5 minutes at full load (lock strike + cameras), sufficient for graceful NVR shutdown and emergency egress. Verify your specific battery and load before deployment.
What is the difference between 'supervised' and 'monitored' outputs?
Supervised outputs include a volt-free relay contact (hardwired) that reports presence/absence of DC voltage. Monitored outputs add remote SNMP or IP reporting (network-based) of voltage level, current draw, temperature, and battery status. Supervised is essential and always required; monitoring is optional but highly recommended for large installations where manual checking is impractical. Altronix managed supplies include both capabilities.
Should I use 12V or 24V supplies for my system?
24V is industry standard for access control (locks, readers) and most surveillance head-ends, offering better voltage regulation over long cable runs (less voltage drop). 12V is older, cheaper, and still used for older equipment and small single-camera installs. Choose based on your camera and lock equipment specifications—do not mix 12V and 24V supplies in the same system unless you have independent output banks and external regulators. Standardize across all sites for maintenance simplicity.
