Products Affected: R-454B products: Furnace/Furnace coil/Outdoor Split combinations Fan coil/Outdoor Split combinations Small Package Products (SPP)

Situation: It is important to identify the system to know what to expect when it comes to the A2L sequence of operations. There are several different scenarios depending on the type of equipment. Once the detected refrigerant level reaches the alarm level specified in Table 1, the system will begin its dissipation mode. Except for Midea multi-family systems, once the refrigerant leak reaches the alarm level specified in Table 1, the compressor immediately turns off and dissipation begins. There will be no call for the compressor in either cooling or heating for fifteen (15) minutes. With the blower running, and a leak large enough to be detectable, the charge of the system will leak out in this timeframe. After the fifteen (15) minute dissipation mode is completed, the compressor can come back on unless the pressure is too low (pressure switches if applicable). During dissipation mode, depending on the system and scenario (see Table 1), auxiliary heat will cycle on before the compressor comes on to continue the heating cycle.

Communicating: In a communicating system, the system heating device (furnace or electric heat) will turn on five (5) minutes after the system sees the detected refrigerant level drop below 20% of the LFL (Lower Flammability Level). After ten (10) minutes from the beginning of dissipation mode, if the detected refrigerant level is still above 20% of the LFL, the dissipation system determines the sensor is faulty. If the sensor is faulty, the furnace or electric heat will still cycle on and off allowing the heating cycle to continue.

Non-communicating: In a non-communicating system, the system heating device (furnace or electric heat) will turn on ten (10) minutes after the system sees the detected refrigerant level drop below 20% of the LFL. After fifteen (15) minutes from the beginning of dissipation mode, if the detected refrigerant level is still above 20% of the LFL, the dissipation system will determine that the sensor is faulty. If the sensor is faulty, the furnace or electric heat will still cycle on and off allowing the heating cycle to continue. Quality and Continuous Improvement Only trained and qualified personnel should design, install, repair and service HVAC systems and equipment. All national standards and safety codes must be followed when designing, installing, repairing, and servicing HVAC systems and equipment. It is the responsibility of the Dealer to ensure local codes, standards, and ordinances are met.

Midea multi-family: In Midea multi-family systems, the dissipation system will function differently. Once detected refrigerant level is above 10% of the LFL, dissipation mode begins. Dissipation mode will run for five (5) minutes. At the end of those five (5) minutes, operations will resume if the detected refrigerant level drops below 10% of the LFL. If the sensor is determined to be faulty, then the system will run in dissipation mode until the sensor is replaced (no cooling or heating operation will be allowed).

See attached bulletin for all the information.