Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 1042

FDC-HKXR
LP,HP-B controls
Under these controls, the high and low level pressures are controlled with the solenoid valves, outdoor fan and other so as to
operate the outdoor unit in the optimum condition in accordance with changing load on the indoor unit.
Operation patterns consist of the following 12 types and respective functional parts are controlled per each pattern.
Table of operation patterns and operations of functional parts
Operation Four-way valve
Pattern 20SS
A1
A2
B1
B2
B3
C1
C2
D1
D2
D3
E1
E2
Notes (1) and mean ON and OFF respectively.
(2) Hi and Me mean the high and medium temperature operations respectively.
(3) When the fan motor FM01 is in the Me mode, the solenoid valve SV3 is interlocked via a relay. (SV2 open)
• LP control
If the pressure switch [63L: 1.96 close/2.75 open MPa (20 close/28 open kgf/cm
by one step in the direction of A1 to E2 so as to raise the low level pressure by controlling the heat exchanger capacity.
• HP-B down control
If the pressure switch [63H
control and the operation pattern is changed by one step in the direction of E2 to A1 so as to lower the high level pressure by
controlling the heat exchanger capacity.
• HP-B up control
If the pressure switch [63H
control and the operation pattern is changed by one step in the direction of A1 to E2 so as to raise the high level pressure by
controlling the heat exchanger capacity.
• Setting the initial operation pattern
When the compressor is started, the operation starts wish one of the following
operation patterns in accordance with the indoor load.
• Timing to change operation pattern
Operation pattern is changed by one step at the actuation of the pressure switch (63L,
63H or 63H ). Once the operation pattern is changed, the same operation pattern is
3 4
maintained for 2 minutes.
However, when the frequency which was requested from the indoor side has changed 20 Hz or more, the operation pattern is
changed by one step at the actuation of the pressure swich even if it is within 2 minutes.
• Changing of operation pattern after a larger change of load
When the indoor load has changed largely like a case when scales of
heating/cooling loads have been inverted, for example, the operation
pattern is changed as follows.
1040
20SL SVS
: 2.11 close/2.50 open MPa (21.5 close/25.5 open kgf/cm
3
: 1.86 close/1.67 open MPa (19.0 close/17.0 open kgf/cm
4
Solenoid Valve
SVL SV2 SV3
2 )] is actuated, the operation pattern is changed
)] is actuated, it enters the HP-B down
2
2 )] is actuated, it enters the HP-B up
Change from heating large to cooling large
Change from cooling large to heating large
Fan motor
FM01 FM02
HI HI
HI
HI HI
HI
Me
HI HI
Me
Me
HI
HI HI
HI
HI HI
Indoor load Initial operation pattern
Cooling only A1
Cooling > Heating A1
Cooling = Heating B1
Heating < Cooling C2
Heating only D1
Operation pattern
To A1
To D3