Safety systems protect life and property from damage or loss due to accidents. For equipment, the degree of protection should be based on the value and criticality of the facility.
Personnel safety is covered rigorously in the NEC and many other standards. Defining this degree requires an in-depth knowledge of the installation and its function.
The following questions should be considered when designing these systems:
a) How long will it take to replace the equipment and at what cost?
b) Can the function of the facility be performed elsewhere?
c) Loss of what key component would result in operation interruptions?
Safety systems can be as simple as a manually operated emergency power-off button, or as complex as a fully interlocked system. However, the more complex a fully integrated system becomes, the higher the probability of system confusion or failure.
Typical systems include the following functions:
— Smoke and fire protection
— Environmental control
— Smoke exhaust
— Fire extinguishing
— Emergency lighting
The interfacing of a safety system is generally unique for each installation and requires a logical design approach. Through a well-defined logic matrix and sequence priorities, it is possible to develop a system that can be maintained, modified, or expanded with little confusion and minimum expense.
Generally, safety systems operate from 120 V ac, 24 V ac, or 24 V and 12 V dc. In any case, these systems must remain powered at all times. The quality of the power supplied to these systems is as important as that of the power delivered to the IT system.
Disturbances in the power supply of the safety system can cause shutdown of the protected system.