Troubleshooting Power Supplies for Access Control Systems

troubleshooting power supplies for access control systems

Additionally wire handling and routing during the installation are essential areas of concern. Improper handling of materials will result in wasted material and man-power; and could possibly result in damage to the wire. Inappropriate routing will result in a non-code compliant installation which has legal and ethical ramifications.

So in the case of my service call, I had the opportunity to rethink, or perhaps more accurately actually address the power supply specification and the power distribution and management aspects of the project which had been initially overlooked.

This system was inadequately powered; there was no power distribution scheme, and system and power supply status were not being monitored remotely or by the end-user.

Having extensive experience with risk assessment, loss prevention and litigation, thankfully we were able to get things re-secured without an attack, robbery or injury occurring first.

The idea is not so much doing it right the first time in case there is a crisis, as it is to follow best practices to avoid a problem from occurring at all.

The access control industry has evolved dramatically, and the choice of product is amazing. For some applications, centrally located power supplies are preferred, while on others, power supplies are best deployed on a door by door basis.

Door by door deployments can be indicated when the system grows door by door over an extended period of time, or when the size of the site would mean pulling long lines that would create voltage drop issues.

Also for certain specialized locking solutions, specifically Electric Latch retraction on exit devices, the in-rush current and manufacturers’ installation guides force power supplies to be deployed near the locking devices.

Where a system is pre-planned, where the structure’s architecture or usage, where system component security are issues (putting a power supply out by a door would invite tampering while securing it in a electrical closet wouldn’t), a centralized approach to power supply deployment may be preferred.

Centrally locating power supplies also simplifies providing line voltage and connection of Fire Alarm interfaces to the power supplies. Fire alarm interfaces are mandated for certain locking arrangements to ensure safe egress in the event of a fire.

Typically an access control system will require power to a door controller, a card reader and an electric locking device at each door.

By providing individually fused circuits, a failure on an individual device does not produce a failure of the entire system, and it also expedites troubleshooting and repair. Without fused circuits, a failure on one door can possibly bring down the whole system.

We also could have implemented monitoring features available through the access control system to email if power or communications were lost.

Many power supplies are provided with monitoring outputs specifically for this purpose.

Our project had a backup battery on the controller, so the controller continued to function for a while before it finally crashed. A simple loss of AC power alarm would have alerted us in enough time to take action.

Following is a listing of some of the power supplies available for access control applications.


SCHLAGE PS900 Series

The PS900 Series is a consolidated line of power supplies and accessories that offers enhanced flexibility and functionality. In addition, the PS900 is easy to order and install.

The full line is UL 294 certified, the industry standard for reliability and performance.

The PS900 Series can be used in a variety of applications to convert high voltage AC power into the low voltage DC outputs required by most access control devices.

The PS900 Series of power supplies protects devices downstream by providing Class 2*, filtered, and regulated power. Once power is converted to low voltage DC, the PS900 Series offers a variety of distribution options, including basic fuse protection, simple relay, and advanced logic providing complex sequencing and timing functions.

* PS906 can provide Class 2 rated outputs when used with 900-8P distribution board.

Three models of the PS900 Series are available. All convert high voltage 120 VAC- 240 VAC (50-60 HZ) power to regulated and filtered low voltage power. Output can be field configured to either 12 VDC or 24 VDC.

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