Proper Power Supplies Ensure Peak Performance

Line condition – Most fire and security system power supplies are known as switching power supplies. These units convert power from an AC line into the DC voltages needed to operate a security system.

A typical switching power supply does not draw its power from the AC line smoothly. It actually draws sudden gulps of current, creating uneven loads on the AC power lines. In instances when a lot of equipment is utilizing switching power supplies, it is common for wiring to overheat and trip circuit breakers because of the way they gulp power. Quality power supplies have circuitry that smoothes out the gulps to keep the AC line better balanced.

Installers know that video equipment is susceptible to damage by transient voltages and surge currents. Noise problems are best handled by a distributed power supply that has built-in protection for these types of events.

Higher quality supplies incorporate sophisticated surge protection components into products. The protection module inside the supply should employ the latest technology to manipulate these potentially damaging voltages.

These advanced modules have three stages of protection that work in concert to either bar entry, redirect or absorb damaging energy. The first stage of protection reflects energy back down the supply line barring it from entering the supply. The second stage rapidly redirects errant voltages to ground, while the third stage suppresses remaining currents and spikes. In addition to shielding the power supply from this harm, the module also may protect adjoining equipment by connecting its feeds through its protection circuits.

Environment – Installers should de-rate power supplies based on the ambient temperature of the installation room.  Unless the manufacturer specifically states the operating temperature range in the product’s technical documentation, power supplies are generally current rated at a room temperature of 20° C (or 68° F).

Another piece of advice offered by experts is to derate power output 5W for each degree the room ambient will be over 20° C.

Considerations should be made for air circulation as well. Most power supplies are constructed with venting in order to allow the release of heat generated from within the unit’s enclosure. This heat should not build up around the supply.  Room selection, interior placement and available ventilation should be considered so adequate airflow around the supply will always be present.

Humidity is another concern for indoor-rated supplies. The best units are rated for 90 percent or more relative humidity. Some supplies are rated to withstand extreme outdoor conditions. They are contained in a sealed enclosure that should be made from durable nonmetallic polycarbonate material with stainless-steel or brass hardware. These tend to be mounted near loads such as outdoor cameras and complement the professional appearance of modern outdoor domes.

Safety – Power supplies that offer robust protection features should always be chosen to keep the installer and end users out of harm’s way. The best supplies have fused power disconnects to cut primary power to the supply in the event of overload, and so it can be easily serviced in a safe manner.

Source of product – The most trustworthy products are developed by manufacturers with a proven track record of quality and product solutions verified through rigorous testing. Power supply manufacturers that also produce the control units for fire and security systems can better assure system compatibility, given their access to system design detail that is not publicly available.

For the complete version of this story, see the November issue of Security Sales & Integration magazine.

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