Installation and User Guide for Senva TG Series Toxic Gas Sensor

Quick Guide

The Senva TG Series Toxic Gas Sensor is designed to detect gas concentrations and communicate via BACnet/Modbus or Analog outputs. Key installation requirements include using wires rated for 75°C or above, de-energizing power before installation, and sealing conduits to prevent condensation and airflow interference. The device requires a warm-up time of up to 2 minutes after power is applied.

Installation

The sensor can be installed as a Wall Mount, Duct Mount, or Remote Mount unit.

• Wall Mount: Locate away from drafts. Mount 3-6 feet above the floor for most gases (CO, NO2, CO2, Oxygen, H2S). Mount Methane, Hydrogen, and Ammonia sensors within 1 foot of the ceiling. Propane sensors should be 1-3 feet above the floor. Refrigerant sensors should be 6 inches above the floor.
• Duct Mount: Drill a 3/4 inch hole in the duct. Install using the provided gasket and screws. The pickup tube ensures adequate airflow.
• Remote Mount: Use the TGx-REM kit for separate mounting heights. Replace the sensor board in the primary unit with the extender board, connect via the provided RJ45 cable, and plug the sensor board into the remote enclosure.

Wiring

Ensure all wiring complies with local electrical codes. Use a Class 2 LPS power supply or greater (15-30VDC or 24VAC).

• BACnet/Modbus: Communication wires can be daisy-chained. Use shielded twisted pair wire (14-26 AWG). Total wiring runs should not exceed 4000 feet. Use built-in EOL termination resistors if necessary.
• Analog: Connect to the appropriate inputs/outputs for 0-5V or 0-10V circuits.
• Relays: Fan and alarm relays are available for external control. Ensure fan relay set-points are uniform if multiple sensors are wired in parallel.

Operation

The device features an LCD display and LED indicators. Green indicates normal readings, Yellow indicates gas concentration above the fan set-point but below the alarm set-point, and Red indicates levels above the alarm set-point. The buzzer can be silenced by pressing all three buttons simultaneously.

Maintenance

Periodic maintenance is required to ensure accuracy.

• Every 6 Months: Retest and recalibrate H2S, Ammonia, and Refrigerant sensors using NIST traceable reference gas. Visually inspect for damage and clean exterior intake ports.
• Annual: Conduct a bump test for Methane, Propane, and Hydrogen. Retest and recalibrate Oxygen, CO, and NO2 sensors.
• Sensor Replacement: Power down the unit, remove the old element, plug in the new element, and re-apply power.

Troubleshooting

If the device is not functioning correctly, check the following:

• No output: Verify wiring and power supply requirements.
• Sensor reading error: The sensor may be contaminated or at the end of its life; replace the sensor element.
• Relay function issues: Verify set-points and test gas concentration. Ensure there are no drafts during testing.
• Chirping noise: Indicates a faulty or missing sensor; replace the sensor element.
• Refrigerant sensor unstable: Requires 1-3 hours of runtime post-installation to stabilize.