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A manufacturer’s installation wiring drawing routes wires
and shows connections in a certain manner to accommo-
date supervision requirements. Any variance from the
manufacturer’s drawings might cause a portion of a circuit
to be unsupervised and, if an open or short circuit fault
occurred, it could prevent the circuit from being able to
perform its intended function without giving the required
trouble indication.

The rules of supervision are not very complex. However,
unless an installer is experienced in fire alarm system instal-
lations, he or she would not likely be familiar with them.

Smoke detector manufacturer’s installation drawings will
show how their detectors are to be connected into a system.
However, a manufacturer’s drawings may not show how
devices located on the same floor, but served by a different
riser (vertical wiring run), should be connected. The dia-
grams on the following page should be considered as typi-
cal initiating device circuits utilizing smoke detectors. They
are offered to illustrate proper and improper installation
wiring and termination techniques. Since there are always
exceptions to typical installation drawings, experienced
installers use the primary rule of installation wiring: Follow
the manufacturer’s instructions, and meet the local codes.

Figure 12 illustrates improper wiring of smoke detector “A”.
This wiring method is referred to as “T-tapping.” This com-
mon installation error is often made in riser wiring as well
as single floor wiring. The smoke detector may operate
properly under alarm conditions. If it becomes disconnect-
ed from the 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 supervi-
sion, and the fire alarm control panel to indicate trouble.

Smoke detectors should be connected to supervised instal-
lation wiring in a manner that ensures electrical supervision
of the device. Removal of a detector from its associated ini-
tiating circuit should cause the loop to open, resulting in a
trouble condition. The required termination at the smoke
detector may involve either screw terminals or wire pigtails.
Regardless of the method utilized, removal of the smoke
detector or a single installation wire must open the initiat-
ing circuit and result in a trouble signal at the control panel.

Screw termination of either side of the initiating circuit may
require only one or two screws. Figure 14 is an example of
proper termination when one screw terminal is used. Note
that the installation conductor has been cut before termina-
tion. This assures full supervision of the smoke detector.

Figure 15 details common connection errors. In both exam-
ples, removal of the smoke detector wire does not open the
initiating circuit. The fire alarm control panel will not rec-
ognize a trouble condition, and the detector that has been
deliberately or inadvertently disconnected will be disabled.

Smoke Detector “A”

Smoke Detector

Smoke Detector

Smoke Detector

Smoke Detector

Smoke Detector

Figure 12: Incorrect Wiring Method

Figure 13: Correct Wiring Method

Figure 14: Proper Termination

Figure 15: Improper Termination

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 ...

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