background image

After all detectors have been
installed, test the complete
system to ensure that no
wiring faults exist, and that all
parts of the system operate as
intended. A complete system

checkout consists of testing each detector at its installed
location and following the panel manufacturer’s instruc-
tions for system checkout. Also, refer to NFPA 72 for addi-
tional information.

Where to Place Detectors

Detector placement is critical to early warning functions.
To provide effective early warning of a developing fire sit-
uation, smoke detectors should be installed in all areas of
the protected premises. Total coverage as defined by NFPA
72 should include all rooms, halls, storage areas, base-
ments, attics, lofts, and spaces above suspended ceilings
including plenum areas utilized as part of the HVAC sys-
tem. In addition, this should include all closets, elevator
shafts, enclosed stairways, dumbwaiter shafts, chutes and
other subdivisions and accessible spaces.

Fire detection systems installed to meet local codes or ordi-
nances may not be adequate for early warning of fire.

A

P

P

L

I

C

A

T

I

O

N

S

 

G

U

I

D

E

:

 

S

Y

S

T

E

M

 

S

M

O

K

E

 

D

E

T

E

C

T

O

R

S

8

Figure 16 is an example of properly connected
smoke detectors provided with pigtails. This
method of termination supervises all wiring to
the point at which it connects to the detector.

Figure 17 shows an incorrect pigtail connec-
tion. This is a form of “T-tapping” discussed
earlier. Note that the conductor between the
wire nut (or splice) and the detector is unsu-
pervised, and could be cut or disconnected
without resulting in a trouble signal.

Wireless Systems

Wireless smoke detectors do not require any
field wiring as the power for the initiating
devices is contained and incorporated within
the device. Removal of a wireless smoke detec-
tor initiates a distinct tamper or trouble signal.
Follow the instructions in the manufacturer’s
installation manual for wireless systems.

Installation Do’s and Don’ts

Do:

• Verify that 2-wire smoke detectors to be

used have been tested and UL listed for
compatibility with the equipment to
which they are connected. If necessary,
contact the manufacturer for this informa-
tion.

• Locate any end-of-line devices electrically

at the end of the circuit, beyond all initi-
ating devices (not at the control unit,
except in a Class A installation).

• Use caution when utilizing 2-wire detec-

tors with integral relays, because they

may require more power than the initiating device cir-
cuit can supply. This could result in the inability of the
relay to control auxiliary equipment to which it is con-
nected.

• When using wireless detectors, follow the manufactur-

er’s installation instructions to assure proper radio
communication between the smoke detector and the
control panel.

• Observe polarity when required.
• Protect detectors against contamination during con-

struction or renovation.

• Carefully follow the manufacturer’s installation

instructions.

Don’t:

• “T-tap” smoke detectors or circuit conductors, except

when specifically permitted by the manufacturer as
part of an intelligent/addressable system.

• Loop uncut installation conductors around screw ter-

minations.

• Exceed the maximum resistance permitted for the ini-

tiating device system.

• Exceed the number of 2-wire detectors allowed on a 2-

wire initiating circuit (specified by UL).

Wiring and System Checkout

As required for all installation wiring of fire alarm systems,
check the detector loop wiring for grounds, short circuits,
and open faults before the system is placed into operation.
Each detector should be tested in accordance with the
manufacturer’s instructions.

When using wireless detectors, verify the radio signal trans-
mission strength in accordance with the installation manual.

Section 4

Proper Detector
Applications,
Placement and
Spacing*

*The guidelines in this section of the guide are adapted from Standards published by the National Fire Protection Association, Quincy,
Massachusetts, USA. These standards include NFPA 72, National Fire Alarm Code; NFPA 70, “National Electrical Code”, Article 760; and NFPA
90A, “Installation of Air Conditioning and Ventilating Systems”.

Smoke

Detector

Wire Nut

Figure 16: Pigtail Connections –
Correct Wiring Method

Figure 17: Pigtail Connections –
Incorrect Wiring Method

Some codes or ordinances have minimum objectives such
as capturing elevators or preventing circulation of smoke
through the HVAC systems instead of early detection of fire. 

A user should weigh the costs against the benefits of
installing a complete fire detection system when any detec-
tion system is being installed. The location, quantity and
zoning of detectors should be determined by what objec-
tives are desired rather than the minimum requirements of
any local codes or ordinances.

“Total coverage”, as defined in NFPA 72, is the definition
of a complete fire detection system. In some of the speci-
fied areas of coverage, such as attics, closets, under open
loading docks or platforms, a heat detector may be more
appropriate than a smoke detector. Careful consideration
should be given to the detector manufacturer’s instructions
and the following recommendations in this guide.

In general, when only one detector is required in a room or
space, the detector should be placed as close to the center
of the ceiling as possible. Central location of the detector is
best for sensing fires in any part of the room. If a center
location is not possible, it may be placed no closer than 4
inches from the wall, or if listed for wall mounting, it may

Smoke

Detector

Wire Nut

Summary of Contents for A05-1003-002

Page 1: ...A P P L I C A T I O N S G U I D E System Smoke Detectors ...

Page 2: ...ectors Have Limitations 5 Section 3 Typical System Layout 5 Electrical Supervision 5 Class B Circuits 5 Class A Circuits 6 Wireless Circuits 6 General Zoning Guidelines 6 Fire Safety Functions 6 Smoke Detector Installation 6 Wiring Installation Guidelines 6 Typical Wiring Techniques 6 Wireless Systems 8 Installation Do s and Don ts 8 Wiring and System Checkout 8 Section 4 Proper Detector Applicati...

Page 3: ...e Council ICC for the purpose of combining the codes produced by the above three organizations into a single set of model building and fire codes ICC s International Building Code and International Fire Code were first published in 2000 and have been adopted by some states Testing Laboratories Testing laboratories test smoke detectors control panels and other components of fire alarm systems to ve...

Page 4: ... number of ionized particles in the chamber is reduced This reduction in the ionized particles results in a decrease in the chamber current that is sensed by elec tronic circuitry monitoring the chamber When the current is reduced by a predetermined amount a threshold is crossed and alarm condition is established Changes in humidity and atmospheric pressure affect the chamber current and create an...

Page 5: ...f insects dirt drywall dust and other forms of contamina tion into the sensing chamber can also reflect light from the light source onto the photosensitive device Electrical transients and some kinds of radiated energy can affect the circuitry of both ionization and photoelectric smoke detectors and be interpreted by the electronic cir cuitry to be smoke resulting in nuisance alarms The allowable ...

Page 6: ...ors such as flame detectors heat detectors and other detection devices may be used The application of these special types of detectors should be based on an engineering survey and used in accordance with the manufacturer s installation instructions provided Smoke Detectors Have Limitations Smoke detectors offer the earliest possible warning of fire They have saved thousands of lives in the past an...

Page 7: ...our hours General Zoning Guidelines The faster the source of an alarm can be pinpointed the faster action can be taken Although formal rules for zon ing are not given in fire protection codes except for wire less devices where each smoke detector must be individu ally identified it is always sensible to zone any system that contains more than a small number of detectors Experienced detector instal...

Page 8: ...installation wiring loop beyond the T tap however the detector would not function and no trou ble condition would occur NOTE T tapping may be permitted with some intelligent fire alarm systems Refer to manufacturer s recommendations Figure 13 illustrates the correct installation wiring method for smoke detectors None of the connections can be bro ken without opening the circuit causing loss of sup...

Page 9: ...instructions to assure proper radio communication between the smoke detector and the control panel Observe polarity when required Protect detectors against contamination during con struction or renovation Carefully follow the manufacturer s installation instructions Don t T tap smoke detectors or circuit conductors except when specifically permitted by the manufacturer as part of an intelligent ad...

Page 10: ...tor incorporates a microprocessor controlled air intake fan and filter that allows the unit to be installed in areas where ordinary detectors cannot be used Filtrex is an intelligent smoke detector that removes airborne particles before they reach the sensing chamber It is ideal for textile mills dusty manufacturing facilities paper mills and recycling centers For more information see System Senso...

Page 11: ... the sys tem into alarm after the alarm condition was cleared System detectors latch in alarm They do not reset until power is momentarily disconnected This makes it conven ient to identify the location of a detector that caused the control panel to alarm In addition system detectors are specifically designed to connect to a panel Two wire detec tors require a UL compatibility review to verify tha...

Page 12: ...and on intermediate levels of the racks adjacent to alternate pallet sections shown in NFPA 72 1999 A 2 3 6 5 A consultant s judgement may be required for specific installations Partitions Partitions and many types of large tall equipment standing on the floor can block the flow of smoke toward detectors Any partition or similar obstruction that is less than 18 inches 45 cm from the ceiling should...

Page 13: ...if the contents are espe cially valuable for example sophisticated and expen sive machinery or irreplaceable records detectors should be placed closer together Detectors in Air Handling and Air Conditioning Systems See NEMA Guide for Proper Use of Smoke Detectors in Duct Applications and NFPA 72 National Fire Alarm Code for more specific information Detectors in Above Ceiling Plenum Areas Includin...

Page 14: ... unit specified range then follow the manufacturer s recom mended procedure Restore zone or system at the completion of testing Notify the proper authorities that testing has been com pleted and the system is again operational Refer to paragraph 7 4 1 of NFPA 72 for additional infor mation To assure that each smoke detector is within its listed and marked sensitivity range it should be tested usin...

Page 15: ... silenced the problem unit located and the alarm system controls reset so that the effectiveness of the detection system is restored Make sure that all the detectors in the zone or pinpointed device s that show an alarm are checked before deciding that it is a false alarm If a fire does exist more than one detector may be in the alarm state although no signs of fire may be evident in the vicinity ...

Page 16: ...en to protect detectors from dust whenever maintenance requires sawing sanding drilling or other dust producing operations in the vicinity of the detector heads to prevent false alarms due to the dust get ting into the detector sensing chambers In new construc tion applications drywall dust contamination affects all types of smoke detectors To help overcome this problem it is strongly recommended ...

Page 17: ...o the owners for a specified break in period after installation in case problems develop Helping the owner set up appropriate Detector Maintenance and Alarm Logs for the system Providing initial instruction and training to the owner s personnel or outside organization which will be monitoring and maintaining the system Providing troubleshooting assistance if nuisance alarm problems cannot be solve...

Page 18: ...t the end of a Class B wire loop to maintain supervision Appendix 1 Glossary of Terms End of Line Relay Device used to supervise power for four wire smoke detectors and installed after the last device on the loop False Alarms An unwanted alarm caused by non smoke contaminants such as dust or insects Fire A chemical reaction between oxygen and a combustible material where rapid oxidation results in...

Page 19: ...utside of its listed sensitivity Smoke Detector A device that detects the visible or invisible particles of combustion Smoothing Algorithms A method of smoothing out a detector s interpretation of sudden short duration increases in obscuration within the sensing chamber intended to reduce the occurrence of nui sance alarms Spot Point Detector A device whose detecting element is concentrated at a p...

Page 20: ...tallation Date Installing Contractor Inspection and Test Date Inspection and Test Performed By Check one Location Action Taken By Date Time Recorded By Fire Trouble Bldg Zone Det Probable Cause Action Taken Name and Date Appendix 2 Fire Alarm Log ...

Page 21: ... 2002 System Sensor The company reserves the right to change specifications at any time A05 1003 002 ...

Reviews: