Mitsubishi Electric PRH-P8MYA Technical & Service Manual page 46

2) Control at heating
a) When the compressor is stopped and during defrosting, the fan is stopped.
b) When the power is turned on, or when the compressor is restarted after being stopped for 30 minutes or longer,
the piping temperature (TH1) determines the fan step.
TH1 > 8˚C
TH1 ≤ 8˚C
c) When the compressor is restarted within 30 minutes, the fan step is the step before the compressor was stopped.
d) When the mode is changed from cooling to heating, the fan step conforms to item b).
e) When returning from defrosting, the fan step is the step before defrosting.
f) Two minutes after the fan was restarted, the fan step is controlled every 30 seconds based on the piping
temperature (TH1).
g) When TH1 is –5˚C or lower, the fan output is made 100%.
• FAN step
The following expression determines the next fan step count nj + 1:
nj + 1 = nj + ∆nj
nj control
• If nj + 1 ≤ 100% nj + 1 = 100%
• If nj + 1 ≤ 20%
• If TH1 < –5 °C
FAN ∆nj
Target evaporation
temperature 10 °C
20 ≤ nj + 1 ≤ 100
(4) Defrosting control
1) When the following conditions are satisfied, defrosting starts:
a) When the integrated compressor operation time has exceeded T
temperature (TH1) is below –10˚C
b) When the integrated compressor ˚C
Piping differential temperature
2) The defrosting prohibit time T
≤ 3 (minutes)
T
2
3 < T
= 15
T
2
Note: When the compressor was stopped during defrosting, T
defrosting end.
3) During defrosting, all the outdoor fans are stopped and the bypass solenoid valve (SV1) is turned ON and the 4-way
valve (21S4) is turned OFF.
4) When the following conditions are satisfied, defrosting ends:
≤ 2 mins
a) T
2
b) 2 < T < 15 minutes
2
c) T =15 minutes
2
5) When the fan and 4-way valve (21S4) are turned ON at the end of defrosting, the heating mode is reset. Two
minutes after defrosting reset, the bypass solenoid valve (SV1) turns OFF.
Fan output = 60%
Fan output = 100%
nj: Current fan step, ∆nj: Displacement step amount
nj + 1 = 20%
nj + 1=100%
T = 19
T > 19 °C
T > 17
–10 –4
∆TH1 = TH10 – TH1
is set as following based on the defrosting time T
1
T 60 (minutes)
1
< 15 40
2
30
Note: T
TH1 ≤ 30°C
TH1 ≤ 8°C continuous 2 minutes
Evaporation temperature TH1
T = 17 T = 15 T = 13 T = 11
T > 15 T > 13 T > 11 T > 8
–3 –2 –2 0
(initial setting 50 minutes) and the piping
1
Current piping temperature
Piping temperature 10 minutes after starting or
10 minutes after returning from defrosting
is reset at the end of defrosting, or by cooling ON command.
1
= 20 minutes is set to recognize the stop as
1
- 43 -
Outputs are all %.
T = 8 T = 6 T = 4 T = 2
T > 6 T > 4 T > 2 T > 0
2 2 3 4
:
2
T≤ 0˚C
10