Fire alarm specialists, inspectors stress importance of surge protection

Jul 10, 2002 12:00 PM

With the increase in popularity of low-voltage technology, electrical systems are more susceptible to transient damage and malfunction, and system designers need to put more thought into surge protection on the AC power line and data/communications lines, which feed into fire alarm systems, according to the National Burglar and Fire Alarm Association (NBFFA) and other industry analysts. Nearly 30% to 40% of all damaging transients enter a system via the AC circuit, but an even greater number come in by way of 48V phone lines.

“Lightning storms render too many fire alarms inoperable, especially in mutlibuilding complexes connected with cable,” says Whitney Crahen, a fire protection specialist who reviews fire alarm plans for the city of San Antonio. “When lightning hits, it can spread hundreds of feet until it finds the path of least resistance – all too often the highly conductive copper wiring that feeds into life safety alarm systems.”

Making the problem of damaging transients more troublesome is the increased use of low-voltage systems. New data circuits that run on 3V can be damaged by relatively small overvoltages that wouldn’t even be enough to power older analog components.

The solution, according to Crahen, the NBFAA, and others is the addition of aftermarket surge protection. According to a May 2000 NBFAA brief, “By installing a surge protection device at the electrical outlet where the transformer is plugged in, you allow the damaging transient to be bypassed to ground before it gets to the control panel, thereby greatly reducing the potential for false alarms and/or damage to the control board. The same is true when you install surge protection on the phone line prior to it entering the panel.”

Although most system components have built-in protection that meets UL requirements, it doesn’t prevent transients from entering sensitive panels, which can disrupt function in life-saving systems like fire alarms. Aftermarket protection, specifically surge protectors that self-restore after dissipating the surge to ground, can help keep these critical systems online. Self-restoring surge protectors wait for a predetermined voltage to be achieved, clamp the overvoltage, shunting it to ground, then automatically reset themselves to passive mode until it happens again. When a catastrophic surge is detected, self-restoring devices “self-sacrifice” like single-use devices, protecting sensitive equipment from damage.

Regardless of what protection device you use, however, taking the step to add aftermarket protection is critical to the proper operation of fire alarm systems. Crahen suggests even going a step further. “Proper surge protection for fire alarms is a requirement,” he says. “And enforcing it will eliminate many future problems.”