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
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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.
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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.
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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.
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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).
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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.
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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.
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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.
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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
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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
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2W-B — 2-wire photoelectric-only version; alarm current limited by the control panel
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2WT-B — 2-wire photoelectric/thermal version
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4WTA-B — 4-wire photoelectric/thermal with an 85 dBA sounder; 35 mA alarm current
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4WTAR-B — 4-wire photoelectric/thermal with sounder and Form C relay; 50 mA alarm current
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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.
