Mitsubishi PWFY-P36NMU-E-BU Service Handbook page 42

2. Frequency control
• The following table shows the frequency change of the inverter compressor during normal operation.
Model
PWFY-P36NMU-E-BU
(1) Pressure limit
The maximum limit of high pressure (Pd) is set for frequency level. If this limit is exceeded, the frequency will
be reduced every 1 minute.
(2) Discharge temperature limit
• Control is performed 1 min after compressor start-up and every 1 min thereafter.
(3) Periodic frequency control
Frequency control other than the ones performed at startup, upon status change, and for protection is called
periodic frequency control (conversent control) and is performed in the following manner.
1 Periodic control cycle
Periodic control is performed after the following time has passed
(a) 1 min after either compressor start up or the completion of defrost operation
(b) 1 min after frequency control by discharge temperature or by pressure limit
2 The amount of frequency change
The amount of frequency change is controlled to approximate the target value based on the set temperature.
3. Subcool control for Heating or Hot water mode (Linear expantion valve <LEV1W(a,b)>)
• The amount of subcool is controlled by LEV1W(a,b) based on the differential between liquid refrigerant piping
temperature (TH22) and condensing temperature every 1 miniute.
• Defrost operation
(1) Booster Unit (PWFY-P36NMU-E-BU)
It stays opened at (LEV1W = 1400 pulse) during defrost operation
(2) HEX Unit (PWFY-P36, 72NMU-E/E2-AU)
It depends on inletwater temperature (TH6) as below.
defrost start
TB142A IN1
Short
Outdoor ambient
temperature(TH7*1)
TH7 -10
Inletwater
temperature(TH6)
High*2
LEV1Wa, b = opened.
SV as bypass circuit for PHEX = shut off.
4. Superheat control for Cooling mode (Linear expantion valve <LEV1Wa,b>)
< PWFY-P36/72NMU-E/E2-AU>
• The amount of superheat is controlled by LEV1W(a,b) based on the differential between gas refrigerant piping
temperature (TH23) and liquid refrigerant piping temperature (TH22) every 1 miniute.
<PWFY-P36NMU-E-BU>
Frequency/heating
25~100Hz 2Hz/sec.
Open
TH7 < -10
Low*2
LEV1Wa, b = closed.
SV as bypass circuit for PHEX = open.
Speed
*1. TH7 - Outdoor unit's thermistor for ambient temperature
*2. High or Low mean as below
Low
16˚C
- 39 -
High
TH6
18˚C