The Leak Detection System (LDS) consists of one or more refrigerant detection sensors and is required in ducted HVAC systems that have more than 3.91 lbs. of A2L refrigerant charge, per safety standard UL 60335-2-40. For any units with more than 3.91 lbs. of charge in a circuit, an LDS will be factory-installed. Having the leak detector installed in the factory by the manufacturer on applicable units reduces the risk of improper installation in the field as well as bypassing the added cost in the field for installation, leading to peace of mind that the right solution has been applied to your unit.

The information shared in this article is to troubleshoot and replace the 454B sensor if needed. 

1. Error Codes displayed for R454B sensor

• 1.b3 / 2.b3

• 1.b4 / 2.b4

• 1.b7 / 2.b7 

• 1.b8 / 2.b8

Locate the sensors in the unit. Verify the sensor is installed correctly and no refrigerant is present in the location of the sensor in alarm. If no leak is present at R454B Refrigerant Sensor location voltage testing is required.

2. Voltage and Communication

The R454B Refrigerant sensor (leak detector sensors) both plug into the main board on CN59 & CN61.  It does not matter which plug the two sensors are plugged into.  From the factory however the Black plug is inserted into the Black socket CN59, and the White plug is inserted into the White socket CN61. The Black plug harness goes to the A2L sensor located in the Heat section and the White plug harness goes to the Return Air located A2L sensor. Verify voltage on the board at both CN59 & CN61 or trace back to the sensor location in current alarm to identify which plug it is connected to on the board. The plug has 5 VDC supply voltage on Red to Black and +2.5/-2.5 VDC pulsing communication voltage from Black to blue, Black to Brown, Black to Yellow. If the voltages are present at plug CN59 or CN61 and also at the sensor in question it will be recommended to replace sensor. 

White Plug Harness is the Return Air Section   /   Black Plug Harness is the Gas Heat Section

3. Order and replacing the R454B Refrigerant Sensor

There is two R454B Refrigerant Sensors available for the Medium Foundation unit. Make sure you know which sensor is needed for correct replacement. The sensors are addressed differently so the board can Identify the failed location. 

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.