Panasonic U-72MF2U9 Service Manual page 41

9. Defrost Control
9. Defrost Control
9-3. Frost Detection
(1) Frost detection does not occur for 5 minutes after operation starts.
(2) Frost is detected when either condition 1 or 2 below is met.
Condition 1: L2 line or below is detected twice, each time continuously for 4 minutes, when the compressor
is operating.
Condition 2: L1 line or below is detected for a total of 60 minutes when the compressor is operating.
-13 (–25)
9-4. Reverse Cycle Defrost
Reverse cycle defrost is performed in systems where only 1 outdoor unit is connected to the refrigerant system.
Special control : Reverse Cycle Defrost features one of the functions of special control.
9-4-1. Start of reverse cycle defrost
When conditions of section "9-2" and "9-3" contents are satisfied, defrost control is started.
9-4-2. Simplified flow of reverse cycle defrost
Whole process
Reverse cycle defrost shall be performed as the flow mentioned below.
(0) Normal operation
(1) Pre-processing time of reverse cycle defrost for 2.5 minutes
(2) Reverse cycle defrost processing time *
(3) Post-processing time of reverse cycle defrost for 2 minutes
(4) Normal operation
Heat exchange liquid temperature °F (°C)
Defrosting operation
end temperature
59 (15)
50 (10)
30.2 (–1)
26.6 (–3)
17.6 (–8)
14 (–10)
The frost detection area is
located under the thick lines
-13.9 (–25.5)
-17.5 (–27.5)
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3WAY VRF SYSTEM 3WAY SYSTEM
Control Functions
Control Functions
(The end temperature
is different from the
above detection
temperature.)
External temperature °F (°C)
L1
L2
1
2
3
4
5
6
7
8
9