Sprinkler Suppression System Selection and Reducing Data Center Risk

November 21 2014

by: Joe Reep, P. E. Mechanical Engineer at TechSite

Site assessments are one of TechSite’s core offerings and a valuable service for IT and

facilities personnel to gain a better understanding of their critical data center infrastructure. In

addition to evaluating and documenting the critical electrical and mechanical elements of a

data center, observations and recommendations for the fire detection and suppression

systems are often included with one of these assessments. Many different approaches have

been taken throughout the industry to protect the critical IT assets from fire with varying

degrees of design complexity, including the use of pre-action sprinkler systems.

Pre-Action Sprinkler Systems in a Data Center

Conventional wet pipe, water based sprinkler systems are never preferred in the data center

due to the inherent risks associated with a potential leak and/or damaged sprinkler head

accidentally discharging water onto the IT equipment. A pre-action system however, is a water

based system that is not only considered acceptable, but is a component of TechSite’s

standard recommendations for protecting a data center from a fire. The following article will

provide a quick summary of a pre-action system, several configurations available, a summary

of operation and the reasoning behind installing such a system in a data center.

A pre-action sprinkler system is different than a wet pipe system typically found in commercial

applications. Instead of water, the pipes are normally filled with compressed air or nitrogen

and water is only released to the space following a combination of events that would indicate

a fire is present in the area(s) being protected. A pre-action system can be used in conjunction

with a clean agent gas suppression system or as the single form of fire protection but requires

a supplemental electric fire detection system to be in place. A pre-action system includes a

specialized control valve that is configured to remain closed until absolutely necessary to delay

a discharge of water onto critical IT equipment. This type of system is highly desirable in a data

center due to the fact that a water discharge, equipment emergency power off (EPO) and the

associated cleanup is often more costly to a business than the fire itself.

Two types of pre-action systems are most common (Single and Double Interlock) and are

similarly designed with the primary differences being the valve that is installed and the

number of events necessary prior to water being released into the pipe. Both a single and

double interlock system require two events to occur before water is discharged to the

protected area.

Single Interlock System

Pressurized sprinkler piping with fusible sprinkler heads.

Single stage pre-action valve requires activation of one of the following prior to opening:

a. Heat Detector

b. Smoke Detector

c. Manual Pull Station

Upon a sprinkler head melting, water fills the pipe and is discharged in the location of the

melted head(s).

A loss of pressure in the system will only generate an alarm

Double Interlock

System

Pressurized sprinkler piping with fusible sprinkler heads.

A loss of pressure in the system will only generate an alarm

Two stage pre-action valve requires loss of pressure in the pipes and activation of one of the

following prior to opening:

a. Heat Detector

b. Smoke Detector

c. Manual Pull Station

Upon a sprinkler head melting, water fills pipes and is discharged from the melted head(s).

Reasons for Installing a Pre-Action Sprinkler System in Your Data Center

Reduces the risk associated with a wet pipe system, e.g. an accidental discharge due to a

faulty or disturbed sprinkler head.

Reduces the risks associated with a deluge system, e.g. an accidental discharge due to a false

smoke and/or heat detection.

Fusible sprinkler heads isolate the location of water discharge to only those being

threatened by a fire.

Eliminates water from being stored overhead in the data center.

By monitoring the pressure within the piping at all times, leaks can be identified through loss

of air pressure, not water leaking in the data center.

Provides supervisory and first stage alarms that may allow enough time for a first responder

to extinguish a fire prior to discharging water in the data center.

Installation and retrofit costs for installing a pre-action system are higher than a standard wet

pipe system. There is also additional maintenance, training and documentation over a

standard wet sprinkler system due to added complexity. Ultimately, a pre-action sprinkler

system provides one of the safest forms of data center protection when contemplating a

water-based system.