Refrigerant Leak Sensor System
Sensor
Sensor Purpose
- UL requirement for units using A2L refrigerant
- Detect the leakage of the refrigerant
- Installed in the air handler unit (for split units)
Who manufactures the R-454B Leak Detection Sensor used
- Danfoss
- The sensors self-calibrate
- The sensor auto resets
- Sensors are calibrated to trip at 15% Lower Flammable Limit (LFL)
- The factory-provided sensor is only set up to detect R-454B
Mitigation Action in the Event of a Leak
When the system detects a leak, the following mitigation actions will be initiated until the refrigerant has not been detected for at least 5 minutes.
- LDS Alarm LED is illuminated
- Disable Compressor Operation
- Disable Electric Heat
- Run the indoor supply fan to deliver a required minimum amount of circulation airflow
- Provide an output to energize Mechanical Room Ventilation (only binary output provision)
If the leak detection sensor has a fault, at the end of its life, or is disconnected, the unit will initiate mitigation actions. Disconnecting the sensor may verify mitigation actions.
Relay Board LDS Alarm LED Light and Location
Sensor Location
Connection Type
- The leak detection sensor is a 6-pin plug. 2-pin 24Vac Power, 2-pin Modbus (not currently used), and a 2-pin contact.
Factory-installed wiring
- Odyssey R-454B refrigerant air handlers are equipped with factory-installed leak detection sensor (LDS) and wired to relay board terminals (J12, J13). The refrigerant sensors are designed to detect the presence of refrigerant in the air handlers. When operating normally and not detecting refrigerant, the sensor binary output is closed, providing a 24 Vac signal to the relay board through terminals J12-3 and J13-3. If either sensor detects a refrigerant concentration above a predetermined threshold, the sensor output opens, removing the 24 Vac signal to the relay board input. This indicates an alarm state. During an alarm condition, the relay board initiates the following mitigation actions:
- Supply fan operates continuously to ensure proper airflow and ventilation.
- Electric heat operation is disabled.
Wiring Diagram
Terminal Description
RB = Relay Board
LDS = Leak Detection Sensor
TB = Terminal Block
UC = Symbio 700 Unit Controller
- RB-J12-1 to LDS1-1 back to LDS1-2 to RB-J12-4 = 24VAC to power the sensor
- RB-J12-2 to LDS1-5 back to LDS1-6 to RB-J12-3 = 24VAC No Alarm LED (0VAC triggers alarm LED on RB)
- RB-J13-1 to LDS2-1 back to LDS2-2 to RB-J13-4 = 24VAC to power the sensor
- RB-J13-2 to LDS2-5 back to LDS2-6 to RB-J13-3 = 24VAC No Alarm LED (0VAC triggers alarm LED on RB)
- TB-1 to RB-J14-4 back to RB-J14-3 to TB-2 = 24VAC No Alarm on the unit controller
Note: When the sensor powers up and the LDS contacts close, J14 contacts close, indicating that the LDS is in its normal operating state. For UC‑J14 to close, both RB‑J12‑3 and RB‑J13‑3 must be supplied with 24 VAC.
The relay board also provides additional hardware outputs that are important for system monitoring and integration. The following table details these outputs, along with their recommended wiring configurations.
| Relay Board Terminal | Type | Leak Detection System | Description |
|---|---|---|---|
J14-1, J14-2 [VENT] | N.O. Dry Contact, Binary Output | Normal | Dry contact binary output is open. |
Alarm | Binary output closed. Can be used to signal an independent ventilation system to provide additional ventilation. | ||
J14-3, J14-4 [ALARM] | N.O. Dry Contact, Binary Output | Normal | Dry contact binary output is closed indicating the refrigerant sensor is operating normal and not measuring a concentration of refrigerant above a specified threshold. |
Alarm | Dry contact binary output is open indicating the refrigerant sensor detecting refrigerant above a threshold. After the refrigerant concentration reduces below a threshold, the alarm state will continue for 5 additional minutes. The Alarm state is also active if the refrigerant sensor fails. The alarm state remains active until the sensor is replaced. | ||
J14-5 Y1o | N.O. 24 Vac, binary output | Normal | Binary output is open, 0 Vac at the output. |
Alarm | Binary output is closed, providing 24 Vac. To be utilized as compressor disabling signal to Electromechanical condensing units when air handler Refrigerant Sensor is in alarm. The output is intended to drive an isolation relay coil to minimize VA consumption | ||
J14-6 Y2o | N.O. 24 Vac, binary output | Normal | Binary output is open, 0 Vac at the output. |
Alarm | Binary output is closed, providing 24 Vac. To be utilized as compressor disabling signal to Electromechanical condensing units when air handler Refrigerant Sensor is in alarm. The output is intended to drive an isolation relay coil to minimize VA consumption. |
Replacement Positions
Alarm
- Diagnostic: Refrigerant Concentration Sensor A (With Symbio Condenser)
If there is no 24VAC between RB-J12-3 and RB-J12-4 or between RB-J13-3 and RB-J13-4, the contact between RB-J14-4 and RB-J14-3 will not close, which will create a "Diagnostic: Refrigerant Sensor Concentration Sensor A" on the Symbio 700 unit controller.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.