System Sensor 4WTR-B Photoelectric i3 Smoke Detector, 4-Wire, Thermal Sensor, Form C Relay

The System Sensor 4WTR-B is a 4-wire i3 Series photoelectric smoke detector with a built-in 135 F fixed-temperature heat sensor and Form C alarm relay for conventional fire alarm systems. Operating on 12/24 VDC with a 10-35 VDC operating range, it features drift compensation, dual-color status LEDs, a 41 F freeze trouble indication, and a removable sensing chamber. The detector provides 2.5%/ft nominal smoke sensitivity, draws 50 A in standby, and includes a prewired mounting base with Stop-Drop 'N Lock installation technology.

System Sensor 4WTR-B i3 4-Wire Photoelectric Smoke and Heat Detector with Relay

The System Sensor 4WTR-B is a conventional 4-wire photoelectric smoke detector with an integrated 135 F (57.2 C) fixed-temperature thermal sensor and Form C relay designed for commercial and institutional fire alarm systems. Part of the System Sensor i3 Series, the 4WTR-B combines smoke and heat detection within a single device, providing an additional method of identifying fire conditions in protected spaces. Its advanced optical sensing chamber detects smoke particles using photoelectric technology, while the built-in thermal element responds when ambient temperature reaches its fixed alarm threshold. The detector includes a Form C dry-contact relay rated at 2 amps at 30 VAC/DC for compatible auxiliary signaling and control applications. Designed for use with conventional fire alarm control panels, the 4WTR-B provides smoke detection, thermal sensing, local status indication, and relay functionality in a compact ceiling- or wall-mounted assembly.

The 4WTR-B operates on nominal 12 or 24 VDC power with non-polarized connections and an operating voltage range of 10-35 VDC. Its low-power electronics draw approximately 50 A during normal standby operation and up to 35 mA during an alarm condition, supporting integration with compatible conventional fire alarm systems and auxiliary power supplies. The detector features 2.5% per foot nominal smoke sensitivity and incorporates microprocessor-controlled drift compensation and smoothing algorithms that automatically adjust detector sensitivity as environmental contaminants accumulate in the sensing chamber. This technology helps maintain consistent smoke detection performance while reducing nuisance alarms associated with gradual dust buildup. The integrated 135 F fixed-temperature heat sensor is self-restoring, while the detector also provides a freeze trouble indication when ambient temperature falls below 41 F (5 C). Dual-color LEDs communicate operating conditions, with a flashing green indicator during normal standby, a solid red indicator during alarm, and distinctive red flashing patterns for sensitivity maintenance and freeze trouble conditions.

The System Sensor 4WTR-B features an installer-friendly plug-in design with a prewired mounting base and Stop-Drop 'N Lock attachment mechanism, allowing technicians to complete electrical connections before installing the detector head. The supplied base accommodates single-gang electrical boxes, 3-1/2-inch and 4-inch octagonal boxes, and 4-inch square boxes with plaster rings, as well as approved direct ceiling mounting using drywall anchors. Its screw terminals accept 14-22 AWG conductors, providing flexibility for conventional fire alarm wiring configurations. The detector measures 5.3 inches in diameter and 2 inches high, including the mounting base, and weighs approximately 7.1 ounces. An optional tamper-resistant feature helps prevent unauthorized removal from the mounting base, while the removable cover and optical sensing chamber simplify cleaning and routine maintenance. The i3 Series also supports simplified sensitivity measurement using the optional System Sensor SENS-RDR infrared sensitivity reader, allowing technicians to evaluate detector sensitivity without removing the unit from its installed location.

The System Sensor 4WTR-B is designed for commercial offices, schools, healthcare facilities, warehouses, retail buildings, and other properties requiring conventional smoke and heat detection. The detector operates within an ambient temperature range of 32 F to 100 F (0 C to 37.8 C) and supports relative humidity levels from 0% to 95% noncondensing. Its combination of photoelectric smoke detection, fixed-temperature thermal sensing, drift compensation, and auxiliary relay operation supports integration with compatible fire alarm control panels and supervised detection circuits. The 4WTR-B is UL 268 Listed for smoke detection in fire protection signaling systems and is intended for installations designed in accordance with applicable NFPA 72 requirements and local fire codes. Unlike the System Sensor 4WTA-B, which includes an integral audible sounder, the 4WTR-B provides a Form C relay without a built-in horn. The 4WTAR-B combines both relay and sounder functionality, while the 4WITAR-B adds an isolated thermal sensing configuration. With its dual-sensor detection, low standby current, flexible mounting options, visual diagnostics, and maintenance-friendly construction, the 4WTR-B provides a practical solution for new conventional fire alarm installations and compatible system upgrades.