System Sensor 2W-B — conventional 2-wire photoelectric smoke detector from the i3 series, supplied as a plug-in head with its mounting base included. The 2W-B is the photoelectric-only model in the family; it has no thermal sensor and no freeze trouble signal.
The detector powers from a conventional 2-wire initiating device circuit, so its alarm current is limited by the control panel rather than by the detector. The plug-in design lets the base be pre-wired and mounted during rough-in and the head fitted later with a Stop-Drop ’N Lock action. Drift compensation and smoothing algorithms compensate for gradual chamber contamination and short-term interference. On a loop equipped with the 2W-MOD2 loop test/maintenance module or a panel running the i3 protocol, the 2W-B provides remote maintenance signaling and the EZ Walk loop test, which gives LED status at each detector to verify initiating-circuit wiring. Sensitivity is read in percent-per-foot obscuration with the SENS-RDR. Head and mounting base ship together.
Specifications
| Model |
2W-B (i3 series) |
| Detection |
Photoelectric; no thermal sensor |
| Wiring |
2-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 |
| Peak standby current |
100 µA |
| Maximum alarm current |
130 mA, limited by control panel |
| Alarm contacts |
None (2-wire) |
| 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″ height (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 the panel’s job: the 130 mA figure is a maximum limited by the control panel, not a current the detector draws on its own. Size the initiating circuit from the panel’s published alarm current, and verify the 2W-B appears on the panel’s compatibility list before ordering.
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No thermal, no freeze trouble: the 135°F fixed thermal sensor and the 41°F freeze trouble signal belong to the 2WT-B and 4WT-B. A 2W-B will never report freeze trouble; do not specify it where a combination photoelectric/thermal head is required.
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Wider temperature range than the thermal models: the 2W-B and 4W-B are rated to 120°F (49°C); adding the thermal sensor drops the ceiling to 100°F (37.8°C) on the 2WT-B and 4WT-B.
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Power-up blink is normal: both LEDs blink every 10 seconds for the first 80 seconds after power is applied. This is the initial status indication, not a trouble condition.
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Remote maintenance needs a companion device: maintenance signaling and the EZ Walk loop test are only available when the loop includes a 2W-MOD2 module or an i3-protocol panel. On a plain conventional panel the detector still works, but those features are inactive.
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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 is installed, which keeps the optical chamber out of construction dust.
Related models
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2WT-B — same 2-wire detector with a 135°F (57.2°C) fixed thermal sensor and 41°F (5°C) freeze trouble indication; temperature range narrows to 100°F
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4W-B — 4-wire photoelectric-only version; 20 mA at 12 V / 23 mA at 24 V alarm current and 0.5 A @ 30 V AC/DC alarm contacts
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4WT-B — 4-wire photoelectric/thermal version
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2WTA-B — 2-wire photoelectric/thermal with an 85 dBA sounder
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2W-MOD2 — 2-wire loop test / maintenance module that enables remote maintenance signaling and EZ Walk
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SENS-RDR — wireless sensitivity reader; RT removal/replacement tool; A77-AB2 retrofit adapter bracket
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.
