When you are installing access control systems, it is easy to focus all your attention on the shiny keypads, sleek readers, and heavy-duty locks. But the real foundation of any reliable installation is tucked away inside a metal cabinet: the power supply unit (PSU). Get the power wrong, and even the best hardware will fail, leading to dropped doors, locked-out tenants, and frustrating call-outs.
At Door Entry Online, our business was founded by experienced installers of access control kits. We spent years in the field fitting access control systems across the UK. Because of this hands-on background, we know exactly what it takes to build a secure, stable system. We only supply professional-grade hardware chosen for true field reliability. That is why our kits are trusted by professional tradespeople and retail consumers alike.
In this guide, we will walk you through everything you need to know about specifying the right power supplies for your next job.
Why Power is the Heartbeat of All Access Control Systems
Think of the power supply as the heartbeat of your installation. It pumps stable, regulated voltage to every reader, controller, and locking device on the network.
If a power supply is underspecified, you will experience voltage drops. This can cause maglocks to lose their holding force, readers to reboot randomly, or keypads to freeze. In modern access control systems, clean and consistent direct current (DC) is absolutely vital. Using the wrong power supply is a shortcut to a failing system and an unhappy client.
12V vs. 24V Power Supplies: When to Use Which?
One of the most common questions from junior installers is whether to use a 12-volt or a 24-volt power supply. The answer depends on the hardware you are fitting and the layout of the building.
- 12V Power Supplies: This is the industry standard for most small to medium access control systems. The vast majority of proximity readers, electric strikes, and standalone keypads run perfectly on 12V DC.
- 24V Power Supplies: You should step up to 24V when you are dealing with heavy-duty hardware or long cable runs. A 24V supply pushes current further without significant voltage drop, making it ideal for large commercial buildings. It is also commonly used for heavy 1200lb maglocks and automated gate motors.
Always check the data sheets for your locks and controllers before deciding. Many modern devices are dual-voltage, but you must set the jumpers correctly on the hardware to match your PSU.
Calculating Power Requirements for Multiple Doors and Maglocks
You cannot simply plug a massive multi-door system into a standard 1 Amp power supply and hope for the best. You must calculate the total current draw of your access control systems to ensure the PSU can handle the load.
To do this, add up the maximum current draw of every single component:
- Controller board: ~300mA
- Proximity readers (x2): ~100mA each
- Magnetic lock: ~500mA
- Exit button with LED: ~20mA
In this simple one-door example, the total draw is around 1020mA (just over 1 Amp). However, you should never run a power supply at 100% capacity. Always build in a 20% to 30% buffer to prevent the PSU from overheating. For this setup, a 2 Amp power supply would be the safest choice.
The Importance of Battery Backups
Power cuts happen. When the mains electricity fails, your access control systems must either fail-safe (open the doors) or fail-secure (keep the doors locked), depending on fire regulations. In either case, the local controllers and readers need backup power to maintain the system's memory and allow secure egress.
This is where a high-quality battery backup is essential. Fitting a reliable 12V DC 7AMP Battery inside your PSU cabinet ensures the system stays online during temporary outages. It provides enough juice to keep controllers active and allow authorised users to open doors for several hours until the mains power returns.
Understanding Relays and Timers in Access Control
Power supplies often come with built-in relays and timers. A relay is simply an electrically operated switch. When a user presents a valid fob to the reader, the controller sends a low-power signal to the relay. The relay then switches the high-power circuit to open the lock. This protects the delicate circuitry of the controller from the heavy electrical load of the maglock.
Timers allow you to set exactly how long the door stays unlocked after a valid read. For a standard office door, 5 seconds is usually enough. For a loading bay or a disabled access route, you might adjust the timer to 15 or 20 seconds.
Secure Your Installations with Trusted Hardware
Specifying the right power supply guarantees your access control systems will run smoothly for years to come. Because we started as installers, we ensure every PSU, battery, and relay we stock is built to last in tough commercial environments.
Explore our "Power Supplies & Accessories" category to find the perfect power solution for your next project. We support UK trade professionals with automatic tiered discounts to help you maximise your margins. Open a trade account today and get 3% off orders over £250, 10% off orders over £750, and a massive 15% off orders over £1,500.
