CHAPTER 8 ALARM SYSTEMS

INTRODUCTION

Many buildings and complexes being constructed today are equipped with some type of intrusion detection and fire-alarm systems. You, as a Construction Electrician, will be challenged to install, troubleshoot, and maintain these systems. Numerous detection and fire-alarm systems are in existence today. In this chapter, we will discuss the function and operation of a typical detection system and various fire-alarm systems. When you are in charge of the installation or maintenance of either a detection or a fire-alarm system, you should acquire reference material, such as manufacturer's literature. If such material is unattainable, refer to Maintenance of Fire Protection Systems, NAVFAC MO-117, that provides an excellent description of several fire-alarm systems. Commercial Intrusion Detection Systems (IDS), Design Manual 13.02, provides descriptions ofvarious intrusion detection systems.

The purpose of any alarm system is either to protect life or property or to detect an intrusion. Alarm systems are set up to (1) give early warning so occupants may evacuate the building and (2) notify the fire department and/or security so they can react as soon as possible.

This chapter will increase your knowledge about security/fire-alarm system installation techniques, operations, and maintenance.

INSTALLATION TECHNIQUES

Before the installation of a security/fire-alarm system is started, a sketch of the building should be prepared or the original blueprints should be obtained. This sketch should be drawn to scale and should show the location of all windows and doors, chases, closets, and so forth. A simple riser diagram showing the various components, such as smoke and heat sensors, control panel, and alarm signals, should also appear on the sketch. When this is completed, the installer can begin the design of the security/fire-alarm system. As a Seabee, it is important to check all supporting documents in the manufacturer's manual before installing a system. If you encounter a problem, contact the NAVFAC alarm systems coordinator.

TYPES OF FIRE-ALARM SYSTEMS

Building alarm systems may be local or local with base alarm system connections. They may be coded or noncoded and may operate either on line-voltage or low-voltage electric power. Their characteristics are described in the following paragraphs.

Coded Alarm Systems

A coded alarm system has audible or visual alarm signals with distinctive pulsing or coding to alert occupants to a fire condition and the location or type of device that originated the alarm. Coding the audible appliances may help personnel to distinguish the fire- alarm signal from other audible signals. Clear and early recognition of the signal should encourage a more orderly and disciplined evacuation of the building. A common characteristic of coded alarm systems, especially of selective coded and multiplex coded systems, is that the coded alarm identification provided by the audible alarm signals is not repeated continuously. Normally, after four complete repetitions of the coded signal, the coding process ends.

Noncoded Alarm Systems

A noncoded alarm system has one or more alarm- indicating appliances to alert the building occupants of a fire but does not tell the location or the type of device that has been activated (manual alarm or automatic protection equipment). The audible or visual alarm appliances operate continuously until they are turned off, until a predetermined time has passed, or until the system is restored to normal. The location or type of device originating the alarm condition can be determined by using an annunciator system. An annunciator is a visual-indicating device.