Hitachi RAM-90QH5, Service Manual, Page: 35 / 83

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Power
Unit 1
Unit 2
Unit 3
Unit 5
Operation
Rush-in prevention
Power
Outdoor fan
Compressor
rotation speed
Turns on
for heating
Compressor requirement
Power relay
Reversing
valve
Cooling
Cooling
Cooling
Unit 3
Cooling
Cooling
1S 1S 1S
100ms
100ms
520
Unit 1
Unit 2
Expansion valve
Unit 3
Unit 4
480
0
520
480
0
520
480
0
520
480
0
Initialization
Power Power Power Power Power
Start sequence
Target speed
Step up control
[SDSTEP]min
—1
/[TSKSPT] sec
[TSKTM1_C
*
]
[SDRCT1_C
*
]
[PSTARTC3
*
]
<TD c N compen Diving control >
[PSTARTC3
*
]
[PSTARTC3
*
]
[PSTARTC3
*
]
Steady speed period
100ms
520
Unit 5
480
0
Initialization
[PSTARTC3
*
]
<TD c N compen Diving control >
<TD c N compen Diving control >
<TD c N compen Diving control >
<TD c N compen Diving control >
TSKTM1, SDRCT1, SDSTEP, TSKSPT, CMAX2, PSTART and PSTARTH are EEPROM data.
MODEL RAM-90QH5
◆ ◆
Expansion valves
• The expansion valves are initialized when power is supplied. The valve for unit 1 is fully closed (–520
pulses), and then that for unit 2 is fully opened (480 pulses). The valve for unit 2 is fully closed (–520
pulses), and then that for unit 3 is fully opened (480 pulses). The valve for unit 3 is fully closed (–520
pulses), and then that for unit 4 is fully opened (480 pulses). The valve for unit 4 is fully closed (–520
pulses), and then that for unit 5 is fully opened (480 pulses). When the valve for unit 1, 2, 3, 4, 5 is fully
closed (0 pulse), start-up is possible.
• The start openings are held during the steady speed period when the compressor is started. After the
steady speed period is finished, the TD control is entered. The start openings are set to PSTARTH when
the outdoor temperature at start 40
°
C or more, and to PSTART when it is less than 40
°
C. PSTART C3 is
used for 3 rooms and 4 rooms operation.
◆ ◆
Compressor rotation speed
• When the compressor is started, the SDRCT1 speed / TSTKTM1 second is held. (Steady speed period)
After the steady speed period is finished, the speed increases at the rate of SDSTEP speed / TSKSPT
second until the target speed is reached.