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Installation of Model HI921 intelligent, addressable thermal detector requires a two -wire SLC circuit. In many retrofit <br />cases, existing wiring may be used. 'T-tapping' is permitted only for Style 4 (Class B) wiring. Model HI921 is polarity <br />insensitive when not used in Class-X mode, which can reduce installation and debugging times. The unit's value is <br />multiplied with built-in ISOtechnology the True Class-X - NFPA 72 compliant SLC isolation feature supporting up to 252 <br />isolation ready devices per loop. When used in mixed mode a maximum of 30 non -isolated devices between isolation <br />devices (wired in polarity -insensitive mode). Each detector fits into one (1) wall -or -ceiling footprint, and only occupies <br />one (1) address on the signal -line circuit (SLC). <br />Model HI921 can be applied within the maximum 50-feet (15.24 m.) center spacing (2,500 sq. ft. [232.3 sq. mJ) per <br />Underwriters' Laboratories. This application guide is based on ideal conditions, specifically, smooth -ceiling surfaces, <br />minimal air movement, and no physical obstructions between potential fire sources and the actual detector. Do not <br />mount detectors in close proximity to heating I ventilation I air-conditioning (HVAC) outlets. Exposed joists or beamed <br />ceilings may also affect safe spacing limitations for detectors. <br />Should questions arise regarding detector placement, observe NFPA 72 guidelines. Good fire -protection system <br />engineering and common sense dictate how and when fire detectors are installed and used. Contact your local <br />Siemens - Fire Safety distributor or sales office whenever you need assistance applying Model HI921 in unusual <br />applications. <br />Be sure to follow NFPA guidelines and UL Listed I ULC Listed installation instructions - included with every Siemens - Fire <br />Safety detector - and local codes for all fire -protection equipment. <br />Model HI921 is a plug-in, (2) two -wire thermal (heat) detector, compatible with Cerberus PRO Modular I FireFinder <br />XLSIV and Model FC9-series FACPs. Each Model HI921 detector has microcomputer -chip technology and highly stable, <br />solid-state electronic circuitry. Model HI921 detectors utilize a modern, accurate and shock -resistant thermistor to <br />sense temperature changes. This electronic -sensing method virtually eliminates thermal lag associated with mechanical <br />temperature -sensing devices and provides almost instantaneous temperature status to the FACP. <br />Model HI921 provides seven (7) field -selectable, pre-programmed temperature settings: <br />Fixed Temperature set points (5) <br />Rate of Rise set points (2) <br />• Fixed 135°F (57°C) <br />• Fixed 145°F (63°C) <br />• Rate -of -Rise: 15°F I min. (8.3°C) at fixed 135°F (57°C) <br />• Fixed 155°F (68°C) <br />• Rate -of -Rise: 15°F I min. (8.3°C) at fixed 175°F (79°C)— — — <br />• Fixed 165°F (74°C) <br />• Fixed 175°F (79°C) <br />Additionally, the Model HI921 detector has the following optional feature: <br />• Model HI921 provides indication of potential water freezing for sprinkler systems, via configuration for reporting a <br />low -temperature warning of 407 (4.4°C). <br />This feature is compatible with Cerberus PRO Modular systems, as well as with FireFinder XLSIV and Cerberus PRO <br />FCIFV922 or FCIFV924 FACPs. <br />Mounting Diagrams I Dimensions I <br />:M. I <br />Model HI921 <br />Siemens <br />usa.siemens.comlfire <br />Smart Infrastructure - Building Products -3- <br />