Centralised vs Distributed Security Power Supplies: Which Architecture Is Better?

Centralised security power places supplies and batteries together, usually in a secure equipment room. Distributed power places smaller supplies closer to the equipment they serve. Neither arrangement wins every project: the better choice follows cable distance, fault consequences, battery servicing and the agreed behaviour of each door during a failure. For NZ installers, the useful comparison is the complete powered circuit, rather than the number of boxes on a drawing.

Define what each architecture actually includes

A central supply can feed individually protected branches to several controllers, readers or locks. Distributed supplies can serve a floor, tenancy or small door group. A hybrid combines central monitoring with local conversion or local standby power. Record these boundaries on the design because a controller in one room and its lock supply in another can create two separate service dependencies.

Do not confuse a distribution board with an additional power source. A fused output module may isolate a branch fault, but every connected branch still depends on its upstream supply. Likewise, two supplies sharing one mains circuit are not independent against loss of that circuit. Draw mains, DC, battery and communication paths separately before describing a design as resilient.

Start with distance and voltage at the load

Cable resistance causes voltage drop when current flows. Calculate the full outgoing and return path using the actual conductor resistance and worst simultaneous current, then compare the minimum voltage at the device with its documented operating range. An idle reading at the power supply cannot establish whether a distant lock will operate during an unlock pulse or low battery condition.

For an illustrative circuit drawing 1 A through a total loop resistance of 1.2 ohms, the drop is 1.2 V. A nominal 12 V source would deliver about 10.8 V before other losses. This is an arithmetic example, not an approved cable size or a prediction for a particular lock. Repeat the calculation using the specified supply and device limits, including battery operation.

Distributed power can shorten the DC run. It also introduces a local mains connection, enclosure, battery and maintenance location. A local DC converter changes the calculation but does not create energy or standby capacity. Check its input limits, efficiency, start behaviour and fault response, rather than treating conversion as a universal cure for a long cable.

Compare faults before comparing equipment quantities

Imagine a twelve-door office supplied from one equipment room. Ask what happens if a branch shorts, the charger fails, a battery disconnects or the room loses power. Individually protected branches may limit one short, while a common charger failure can affect every branch. Confirm protection coordination and recovery using the selected manufacturers' documentation.

A distributed design might divide the same office into three four-door groups. That can reduce the number of doors affected by one local supply fault, but there are now three locations to inspect. If none reports a battery fault, a failed battery may remain hidden until an outage. Distribution improves fault boundaries only when those boundaries are deliberate, monitored and serviceable.

Specify standby power and monitoring together

Prepare a load schedule for every supply. Separate continuous readers and controllers from intermittent lock demand, and include auxiliaries, interfaces and any equipment needed for the intended service. Check whether the published current rating includes battery charging. Powerbox's PB256 documentation distinguishes load and battery current limits; that distinction matters when comparing nominally similar supplies.

Battery capacity, charger capacity and recovery time answer different questions. A larger battery may extend standby but take longer to recharge, exceed the permitted battery range or require another enclosure. Define the required standby scenario first, then use the manufacturer's battery and charging instructions. Do not infer a universal standby duration from battery amp-hours alone.

List which conditions reach the alarm or management system: mains failure, DC failure, low battery, enclosure tamper and branch faults where supported. Allocate a named recipient and response for each. A volt-free fault contact provides an interface; it does not prove the event is configured, supervised or acted upon at the monitoring end.

Choose an architecture using a project decision table

Use the table to ask questions, rather than to select equipment automatically. Record the chosen arrangement, rejected alternatives and the site constraints that drove the decision. On a staged retrofit, retain spare capacity and documented interfaces without assuming future tenants will share the same schedules, voltage or standby requirements.

Keep door safety separate from power convenience

An architecture diagram does not determine emergency egress. For each controlled opening, document the required lock state, local exit operation, relevant emergency interfaces and behaviour during mains loss, battery exhaustion and controller failure. Have the responsible project specialists confirm the arrangement against the applicable building design and exact hardware instructions.

Do not parallel supplies, connect batteries across separate chargers or bridge protective outputs unless the manufacturer expressly supports that configuration. Isolation, earthing, mains installation and enclosure segregation need appropriate design and competent installation. A blog comparison cannot supply a universal terminal-level wiring scheme for different lock and controller combinations.

Commission the complete circuit and leave a service map

Test normal operation with the expected simultaneous load, then repeat the agreed tests under standby power. Measure at the farthest load and record the instrument, circuit identity and operating condition. Test one approved fault at a time, verify which equipment is affected and confirm that fault reporting reaches the correct destination.

Leave an enclosure schedule showing supply model, output voltage, protected circuits, battery arrangement, replacement information and monitoring points. Label both ends of each feed. Include restoration checks so a test does not leave a battery disconnected, a branch isolated or an alarm bypassed. The best architecture is one the next technician can understand and safely maintain.

Equipment selection and technical references

Use these access control options as a starting point for a project specification. The pictured items are equipment candidates, not a pre-approved complete design. Confirm model, accessories, interface support and suitability before ordering.

Related installer guidance: Access control power supply sizing battery backup.

Primary references checked 24 October 2026: powerbox.co.nz technical guidance; www.altronix.com technical guidance.

Get project specification help

Contact Essential Security Supplies with your site layout, proposed equipment and operating requirements. Ask for model-specific technical support or a trade quotation before finalising the design.