10 Considerations When Selecting Power Supplies

Calculating the power requirements of each system's components and how they integrate with one another is critical

To comply with NFPA requirements, there are two classifications of locking devices that need to be addressed: Fail-Safe and Fail-Secure. Fail-Safe locking devices, such as magnetic locks, release when they lose power. Fail-Secure locking devices, such as electric strikes, unlock when power is applied and may be manually released from inside a secured area. This determines the manner in which your power solution removes or provides power and the sequence and timing of each action.

Some systems may also require the installation of panic hardware devices. Upon activation, the devices’ high current power demand can reach up to 16 amps, but not all power supplies can handle these high inrush currents. As a result, you need to specify a power supply designed for this type of application. Some operate a single panic hardware device and require optional modules to add features like timing functions, output relays, fire alarm disconnect or power for additional panic hardware devices. Therefore, these "base" models almost always require additional modules to deliver the functionality you need and may not be cost-effective. More advanced models offer integrated features and supply a comprehensive solution.

6. For Video Surveillance Systems: Video’s constant operation typically places high demands on power supplies. These video power supplies need to deliver a clean and consistent source of 24VAC or 12VDC power to ensure uninterrupted operation. Depending on the video component’s specific power requirements and its location, there is a wide selection of power supplies. They can be wall- or rack-mounted, designed for use indoors or outdoors, and feature AC or DC outputs. Configurations typically range from 1 to 32 outputs and some models offer additional features like 115 or 230VAC input with current ratings as high as 25 amps, power LED indicators, and PTC or fused protected outputs. Certain models provide both 24VAC and 12VDC to power both types of cameras simultaneously.

7. Temperature: Temperature differences due to change of seasons, day or night can often be extreme and can have a direct affect on the performance of both the video components and the power supply when located outdoors. Enclosures for outdoor power supplies should be rated to withstand the elements.

8. Ground Isolation: In some cases, cameras are not equipped with internal electrical ground isolation. Should this be the case, it is important to specify a power supply with this feature.

9. UTP Transceiver Hubs: The use of structured cable has been an inexpensive method for transmitting video and data between head-end equipment and camera systems. The introduction of UTP transceiver hubs with integral camera power make it possible to transmit both video and data via structured cable along with the power needed for the cameras. This is accomplished via video balun/combiners which pass the power and data to the camera and send the video back to the head-end equipment. These devices greatly reduce the time and expense of configuring and installing separate components while helping to minimize bandwidth requirements for large systems.

10. Find Help: Selecting power supplies is a complex process given all the individual equipment and system variables, functionality requirements and compliance issues to be considered. The safest practice to follow is to consult with your dealer/installer and draw on their expertise and field experience.

Paul Rizzuto is Technical Sales Manager for Altronix Corp. All trademarks are the property of their respective owners.