System Sensor 4W-B — conventional 4-wire i3 series photoelectric smoke detector, supplied as a plug-in head with its mounting base included. The 4W-B is the photoelectric-only 4-wire model; it has no thermal sensor and no freeze trouble signal. A 4-wire detector takes operating power from a separate supervised power circuit and reports alarm through dry contacts, so the panel sees a contact closure rather than a change in loop current. That keeps detector power independent of the initiating circuit and makes the 4W-B a common choice where a security or combination panel supplies auxiliary power. Its own alarm draw is modest — 20 mA at 12 V, 23 mA at 24 V — and standby is 50 µA. The plug-in design lets the base be pre-wired and mounted during rough-in, with the head fitted later by a Stop-Drop ’N Lock action. Drift compensation and smoothing algorithms adjust for gradual chamber contamination and reject short-term interference, and wide-angle dual-color LEDs show power up, standby, out-of-sensitivity and alarm. Sensitivity is read in percent-per-foot obscuration with the SENS-RDR. Head and mounting base ship together. Specifications Model 4W-B (i3 series) Detection Photoelectric; no thermal sensor Wiring 4-wire Operating voltage 12/24 V nominal, non-polarized; minimum 8.5 V, maximum 35 V Maximum ripple voltage 30% peak to peak of applied voltage Standby current 50 µA maximum average Maximum alarm current 20 mA at 12 V; 23 mA at 24 V Alarm contact ratings 0.5 A @ 30 V AC/DC Sensitivity 2.5%/ft nominal Operating temperature 32°F to 120°F (0°C to 49°C) Operating humidity 0 to 95% RH, non-condensing Input terminals 14 to 22 AWG, SEMS screws Dimensions (including base) 5.3″ diameter × 2.0″ (51 mm) height Weight 6.3 oz (178 g) Listing UL 268, Fire Protection Signaling Systems LED — power up Green and red both blink every 10 seconds, 80 second initial indication LED — normal standby Green blinks every 5 seconds, red off LED — out of sensitivity Red blinks every 5 seconds, green off LED — alarm Red solid, green off Mounting 3½″ octagonal, 4″ octagonal, single-gang or 4″ square back box with plaster ring, or direct to ceiling Installation notes Alarm current is voltage dependent: 20 mA at 12 V and 23 mA at 24 V. Size the 4-wire power supply and standby battery for the system voltage actually used, allowing for every head expected to be in alarm at once plus 50 µA standby each. Supervise the power circuit: as with any 4-wire detector, loss of detector power must be annunciated as a trouble at the panel — normally by an end-of-line relay at the far end of the power run. A 4-wire detector whose supply fails silently is an unsupervised detector. No thermal, no freeze trouble: the 135°F fixed thermal sensor and 41°F freeze trouble signal belong to the 4WT-B and 2WT-B. A 4W-B will never report freeze trouble. Wider temperature range than the thermal models: the 4W-B and 2W-B are rated to 120°F (49°C); the thermal models are limited to 100°F (37.8°C). Contacts are rated 0.5 A @ 30 V AC/DC: do not switch heavier auxiliary loads directly. Where a higher-rated Form C contact is needed, use a relay model or an external relay. Power-up blink is normal: both LEDs blink every 10 seconds for the first 80 seconds after power is applied — the initial status indication, not a fault. EZ Walk and remote maintenance are 2-wire features: the 2W-MOD2 module serves 2-wire i3 detectors. Use the SENS-RDR to read a 4W-B’s sensitivity. Pre-wire the base: in-line terminals and a large wire entry port allow the base to be wired and mounted before the head goes in, keeping the optical chamber out of construction dust. Related models 4WT-B — same 4-wire detector with a 135°F (57.2°C) fixed thermal sensor and 41°F freeze trouble; temperature range narrows to 100°F 2W-B — 2-wire photoelectric-only version; alarm current limited by the control panel 2WT-B — 2-wire photoelectric/thermal version 4WTA-B — 4-wire photoelectric/thermal with an 85 dBA sounder; 35 mA alarm current 4WTAR-B — 4-wire photoelectric/thermal with sounder and Form C relay; 50 mA alarm current SENS-RDR — wireless sensitivity reader; RT removal/replacement tool; A77-AB2 retrofit adapter bracket, 6.6″ (16.76 cm) diameter Specifications taken from the System Sensor data sheet “i3 Series Photoelectric Smoke Detectors,” document A05-0318-007 (6/09). Manufacturer specifications are subject to change without notice.
