Defrost control

2. Processes and functions

Defrost sequence

Heating operation

(25-minute mask)

1 Frost detection

Defrost start

(reverse cycle defrost)

Defrost in progress

2 Defrost cancel

3 Start-up operation

•Operating frequency: 61.8 Hz

•Outdoor unit fan: OFF

•Electronic control valve: step 300

•4-way valve: OFF

•Indoor unit fan: OFF

Frost detection

1. Outdoor heat exchanger temperature (C1) method (15-minute mask after operation start)

2.Outdoor air temperature is 7°F or above and outdoor heat exchanger temperature (C1) of 0°F or below is detected continuously for 20 seconds.

3.Outdoor air temperature is below 7°F and outdoor heat exchanger temperature (C1) of below (outdoor air temperature -10)°F is detected continuously for 20 seconds.

(2)Defrost cancel

•Defrost end conditions

1.Outdoor heat exchanger temperature (C1) rises to 54°F or higher.

2.Outdoor heat exchanger temperature is 45°F or higher continuously for 1 minute.

3.Defrost time of 10 minutes has elapsed.

(3) Startup operation

After defrost ends, the compressors and outdoor unit fan stop for approximately 40 seconds, then operation begins in heating mode.

SM831148

II-8