Series-3868

Supported Applications

The Dwyer Tell Tale Jr.™ Series-3868 Open Heater Detector is designed to indicate an open heater or other resistive load by monitoring current flow in the circuit. The series provides visual indication via LED models that light when current flows and turn off if current stops, while solid-state switch models provide logic outputs for DC applications or triac outputs for AC applications. These configurations support sending heater data to a PLC or computer having an appropriate power supply.

Operating Conditions & Performance

The Series-3868 operates as a self-powered device, drawing no power from the process and introducing no power loss in the monitored load circuit. Ambient temperature limits vary by output type: Indication Only models operate from 32 to 158°F (0 to 20°C); Logic Output models operate from 32 to 140°F (0 to 60°C); Triac Output models operate from 32 to 104°F (0 to 40°C). A note specifies that the ambient temperature range for LED models is 0 to 70°C, logic output 0 to 60°C and triac output 0 to 40°C at 0.5A with de-rating to 0.35A at 60°C.

Output specifications are defined as Logic: 0.25A @60 VDC max., or Triac: 0.5A @120 VAC. The device features a doughnut-shaped current transformer housing where one heater hookup wire is passed through the center one or more times, providing isolation with no direct contact with power lines.

Configuration Options

The series offers multiple configurations to address specific monitoring needs:

• Housing and Indication: Models include internal red LED (Model 3868-0150), internal green LED (Model 3868-0180), external red LED with a 4 ft (1.2 m) cable (Model 3868-0160), and external green LED with a 4 ft (1.2 m) cable (Model 3868-0170).
• Switch Outputs: Logic output models without an LED include Model 3868-0140, while triac output models without an LED include Model 3868-0130. Both switch variants are provided with a 4 ft (1.2 m) cable.
• Electrical Connections: Standard leads are 4 feet long but may be extended up to 3,000 feet using 22 ga. copper wire if necessary.
• Housing Material and Dimensions: The unit features a black plastic doughnut-shaped current transformer housing with an overall height of 45 mm (1.750 in), width of 37 mm (1.438 in), depth of 24 mm (0.938 in), top width of 13 mm (0.500 in), and a center hole diameter of 19 mm (0.750 in).
• Accessories: Model 3138-0412 Network Snubber is available.

Key Product Differences

Variants within the Series-3868 differ primarily by indication method and output signal type. Indication-only models utilize red or green LEDs, either internal to the housing or external on a 4 ft (1.2 m) cable. Switch action models omit the LED indicator and provide electrical outputs: Logic for DC applications or Triac for AC applications.

When using the triac output model to drive an inductive load such as a relay coil, the Model 3138-0412 snubber network is required. Nylon tie wraps are included with all models to anchor the detector to the wire during installation.