Access Control Power Supply Calculator

Inputs

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Most access-control systems are 12 VDC or 24 VDC. Higher voltage reduces current and voltage-drop percentage for the same wattage.
Number of powered doors/openings included in this power supply load.
Use all openings for continuous maglocks. For electric strikes, use the maximum locks expected to energize together.
Current draw for each maglock, electric strike or electrified lockset while energized.
mA
Card reader, keypad or biometric reader current per opening.
mA
Combined request-to-exit, door-position, PIR, relay or local accessory current per opening.
mA
Controller, expansion board, network module and panel accessory current fed by the same supply.
mA
Extra power-supply capacity before rounding up to a listed DC supply size.
%
Use per-opening for a separate home-run pair to the farthest door. Use total panel load for a shared trunk feeding the whole load.
Copper conductor size used for the voltage-drop check. This is a voltage-drop screen, not an ampacity or listed-cable approval.
One-way cable distance from the power supply to the farthest checked lock/opening or trunk end.
ft
Maximum desired voltage drop to the farthest load. Check device minimum voltage and manufacturer limits.
%
Desired battery-backed runtime at the calculated load.
h
Capacity fraction assumed usable after aging, temperature, discharge-rate and reserve derating.
%

Results

Default result
Edit inputs
Recommended supply size(I_supply)
3A
Pass

next listed low-voltage DC supply size

Also computed

Design current with margin(I_design)2.613A

Total active load(I_load)2.09A

Selected wire drop(VD)Pass4.58%

At or below the 5% target.

Recommended wire area(CM_min)Pass1.62kcmil

nearest listed size: #18 AWG

Load-end voltage(V_load)22.9V

Farthest-leg current(I_leg)0.46A

one active opening

Method notes 3 notes
  • Power-supply load uses simultaneous lock current plus reader/accessory current for every powered opening, then applies the entered margin.
  • Wire voltage drop uses a copper two-wire DC circular-mil shortcut with one-way length; it does not verify listed cable, ampacity, fire alarm interface, door release, egress or local code requirements.
  • Battery Ah uses active load, standby hours, supply margin and usable-capacity derating. Final standby design must follow the access-control/fire-life-safety design documents, listed equipment instructions and local AHJ requirements.

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