Hitachi UTOPIA RAS-4HVRP2E - Ras-(4-6)H(V)(R;N)(C;P)2 E

5 Control System
Device control system
SMGB0136 rev.0 - 07/2021
81
5
5.1.2 RAS-(4-6)H(V)(R/N)(C/P)2E
Control device
Cooling operation
Control Category Purpose of Control
Compressor inverter
frequency
Total indoor units Operating
Capacity
To determine the compressor frequency depending on:
- Difference between Indoor Inlet Air Temperature and Setting
Temperature
- Amount of Temperature Difference Change
- Capacity Ratio between Operating Indoor Unit and Outdoor Unit
Electronic Expansion
Valve for indoor unit Heat
Exchanger
Indoor units Heat Exchanger
SH
Quasi PI Control:
- To determine the indoor units electronic expansion valve opening so
as to keep (Temperature Difference between Indoor Gas Pipe and
Indoor Liquid Pipe = Indoor Gas Pipe Temperature - Indoor Liquid Pipe
Temperature.) at an optimum value.
- To change the indoor units electronic expansion valve opening when
the number of operating indoor units is changed.
Electronic expansion valve
for the outdoor unit heat
exchanger
Capacity control EVO: 480pls (Fully Opened)
Outdoor unit fan Pd control
To control the fan steps so that High Pressure is within a stable
temperature range.
4-way valve control OFF
Control of solenoid valve
for High/Low pressure Gas
Bypass Valve (SVA)
1. Increase in Pd protection
2. Decrease in Ps protection
At Start-up and when High Pressure Increase Protection activated: ON
High and low pressure
control
Shut-off of high and low
pressure in the cycle during
stoppage
SVA: ON (during Operation Stop)
Comp. Preheating Control Crankcase Heater Control
Control device
Heating operation
Control Category Purpose of Control
Compressor inverter
frequency
Total indoor units Operating
Capacity
- PI Control:
To determine the compressor frequency so as to keep High Pressure.
- To determine the compressor frequency from difference between
Indoor Inlet Air Temperature and Setting Temperature and Capacity
Ratio between Operating Indoor Unit and Outdoor Unit when heating
operation is started or the number of operating indoor units is changed.
Electronic Expansion
Valve for indoor unit Heat
Exchanger
Indoor units Heat Exchanger
SC
- To determine the indoor units electronic expansion valve opening so
that the indoor liquid pipe temperature is at an optimum level.
- To change the indoor units electronic expansion valve opening when
the number of operating indoor units is changed.
Electronic expansion valve
for the outdoor unit heat
exchanger
Outdoor unit Heat Exchanger
SH
- Quasi PI Control:
To determine the outdoor unit electronic expansion valve opening
so as to keep the temperature at the top of the compressor at an
optimum level.
- When Operating Indoor Unit Number Changed:
To determine the outdoor unit electronic expansion valve opening from
the compressor frequency ratio before/after the change and Quasi PI
Control.
Outdoor unit fan Ps Control
The fan steps are dependent on Ta in the beginning. After that to control
the fan steps so that Ps is within a stable pressure range.
4-way valve control ON
Control of solenoid valve
for High/Low pressure Gas
Bypass Valve (SVA)
1. Increase in Pd protection
2. Decrease in Ps protection
At Start-up and when High Pressure Increase Protection activated: ON
Compressor Preheating
Control
Crankcase Heater Control