NFPA 72 Chapter 5 Initiating Devices –
Heat Detectors
This is a continuation
on the series of articles about the most important requirements in NFPA 72
National Fire alarm Code Book. Make sure to read the first article NICET Study Guide – NFPA 72 Chapter 4
Fundamentals of Fire Alarm. In
this articles I will discus Heat Detectors and give you the most important code
requirement that you must know about for the exam.
General Requirements for all types of initiating devices:
·
Initiating devices
shall only be installed in accessible locations.
·
Initiating devices
shall be protected if they are exposed to mechanical damage.
·
A mechanical guard
shall be listed for use with the detector.
·
Initiating devices
shall be supported by another means besides their own conductors.
·
Initiating devices
shall be installed in a manner to allow for regular maintenance.
·
Duplicate terminals
shall be provided on the detectors for monitoring the wires for integrity.
·
Heat & Smoke
Detectors Shall not be recces mounted unless they are listed and tested.
·
In a non required
application where detectors are installed to achieve specific fire safety
objective, additional detectors shall not be required throughout.
Heat Detectors General
Requirement
·
Heat detectors shall
be classified by the temperature of operation and marked with a color code
according to the following table
Temperature Classification
|
Temperature Rating
|
Max Ceiling Temp
|
Color Code
|
Low
|
100-134 F
|
80 F
|
Unclolored
|
Ordinary
|
135-174 F
|
115 F
|
Uncolored
|
Intermediate
|
175-249 F
|
155 F
|
White
|
High
|
250-324 F
|
230 F
|
Blue
|
Extra High
|
325-399 F
|
305 F
|
Red
|
Very Extra High
|
400-499 F
|
380 F
|
Green
|
Ultra High
|
500-575 F
|
480 F
|
Orange
|
·
Heat detectors shall
be marked with the listed operating temperature.
·
Spot type heat
detector shall also be marked with the response time index.
·
Combination heat smoke
detector shall be listed for no less than 50ft spacing.
Location of Heat
Detectors
·
Ceiling mounted heat
detector shall be located not less than 4 inch from side wall
·
Sidewall mounted heat
detector shall be located between 4 and 12 inches from the ceiling.
·
Line type heat
detector shall be mounted within 20 feet from the ceiling.
·
In a solid joist
construction heat detectors shall be mounted at the bottom of the joist.
·
In beam construction
detectors can be mounted on the bottom of the beam if the beams are less than
12 inches deep and less than 8 inches on center.
Spacing of Heat
Detectors
Smooth
Ceiling
·
Any point on the
ceiling shall have a detector within 0.7 times the listed spacing.
·
Distance from a detector
to a wall shall not exceed 1/2 of the listed spacing.
·
Heat Detectors Shall
not Exceed their listed spacing.
·
In irregular areas
spacing of heat detector is permitted to be more than listed spacing, provided
that it should be within 0.7 time the listed spacing from a wall.
Beam
Construction
·
The ceiling shall be
treated as a smooth ceiling if the beam is less than 4″
·
When beam is more than
4″ spacing shall be no more than 2/3 of smooth ceiling spacing.
·
When beam project more
than 18 inches from ceiling and more than 8 feet on center. than these pockets
shall be treated as a separate areas.
Sloped
ceiling
·
The first row of
detector in sloped ceiling shall be within 3 ft of the peak.
·
If the slope is less
than 30 degrees, detectors shall be spaced using the height at the peak.
·
If the slope is more
than 30 degree, then the average slope height shall be used except the first
detectors on the peak.
High
Ceiling
·
On ceiling between 10
feet and 30 feet high, the spacing shall be reduced according to table below.
·
The minimum spacing
shall not be less than 40% the height of the ceiling
Ceiling Height Above (Feet)
|
Up to and Including (Feet)
|
Multiply Listed Spacing By
|
0
|
10
|
1.00
|
10
|
12
|
0.91
|
12
|
14
|
0.84
|
14
|
16
|
0.77
|
16
|
18
|
0.71
|
18
|
20
|
0.64
|
20
|
22
|
0.58
|
22
|
24
|
0.52
|
24
|
26
|
0.46
|
26
|
28
|
0.40
|
28
|
30
|
0.34
|
This post should be
part of your study guide for NICET Level 1 and Level 2. Please pay attention to
the two tables above, they are table 5.6.2.1.1 and 5.6.5.5.1 on pages 72-39 and
72-40 respectively, make sure to label these sections. I am sure that these
tables are good candidate for questions on the exam. I will discuss the
requirement of smoke detectors and other initiating devices in upcoming
post. as always please let me know in the comment area below on what you
think about this post and what would you like to see in future articles.
Cheers!!
- Types of initiating devices include:
- Manual fire alarm boxes / Manual Pull Station / Manual Call Point
- Smoke detectors
- Heat detectors
- Flame detectors
- Sprinkler waterflow detectors
- Switches indicating actuation of fire suppression systems
- Valve supervisory devices
- Pressure supervisory devices
- Level supervisory devices
