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detectors installed on a 10 foot (3m) ceiling.

This method provides an accepted, easy to

apply approach, in dealing with high ceiling

applications for generalized fire conditions. It

does not, however, provide guidance for ceiling

heights over 30 feet (9.1m). In such installa-

tions, engineering judgment, the manufactur-

er’s recommendation or detector spacing

approved by the authority having jurisdiction

should be used.

In many applications, Protectowire Linear

Heat Detector is used for electrical activation

of pre-action or deluge type sprinkler sys-

tems. In sprinkler release applications, special

Factory Mutual (FM) spacing requirements

may be required. In some cases, FM spacing

requirements may conflict with the recom-

mendations for high ceilings provided in

NFPA 72. In these situations, general practice

is to utilize NFPA 72 recommendations in sys-

tems involving detection only, and to follow

FM detector spacing guidelines when design-

ing a detection system to be used for sprinkler

system release. In all cases, the final detector

spacing must be accepted and approved by

the authority having jurisdiction.

The reduction of heat detector spacing on

high ceilings as required in NFPA 72, is by no

means universally applied. Several types of

heat detectors including “line-type electrical

conductivity detectors,” more commonly

known as analog line-type detectors, have

been identified in NFPA 72 as an “exception”

to the high ceiling derating requirements.

This “exception” has been promoted on sev-

eral levels to infer that analog detectors have

been excluded from the reduced spacing

requirements due to superior performance.

In actual fact, The Fire Detection Institute Fire

Test Report, which was used as a basis for the

high ceiling derating information contained

in NFPA 72, does not include data on integra-

tion-type detectors and therefore, “exception”

was granted only until such time as data is

developed for this type of detector.

For the purposes of this manual, good system

design dictates that the listed spacing of all

installed heat detectors, regardless of operat-

ing principle, be reduced to compensate for

the effects of ceiling height.

Sloped Ceilings

In areas having a sloped or peaked ceiling, at

least one line of Protectowire must be located

at or within 3 feet (0.9 m) measured horizon-

tally from the peak, but not closer than 4 inches

(10 cm) vertically to the peak. The spacing of

additional runs of Protectowire, if any, should

be based on the horizontal distance projected

down from the ceiling and in accordance with

the type of ceiling construction.

Pre-Action Sprinkler Systems

When Protectowire Linear Heat Detector is

used as the initiating device for pre-action

sprinkler systems, special Factory Mutual loca-

tion and spacing guidelines may be found in

FM Loss Prevention Data Sheets such as 8-29,

which covers Refrigerated Storage Facilities.

As a general rule, FM acceptance criteria for open

area ceiling applications such as that

covered in 8-29, requires that the detector be

installed at a spacing not exceeding the allowable

ceiling sprinkler spacing. The detector

spacing is accomplished by maintaining a contin-

uous run of Protectowire parallel to each branch

line. At the end of each branch line the detector is

run at a right angle (maintaining the appropriate

2.5 inch [6.4 cm] bend radius) across to the next

Figure 5

DETECTOR MAY

E PLACED

ANYWHERE IN

HIS AREA,

BUT NOT CLOSER

THAN 4 INCHES

(102MM)

ERTICALLY TO

THE PEAK.

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 32 33

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