OUTDOOR UNITS
2-14
TC-16001-rev.5
2.11.2 Control System
Cycle Control
(a): Difference between Indoor Inlet Air Temperature and Setting Temperature
(b): Amount of Temperature Difference Change
(c): Capacity Ratio between Operating Indoor Unit and Outdoor Unit
(d): Temperature Difference between Indoor Gas Pipe and Indoor Liquid Pipe
(= Indoor Gas Pipe Temperature - Indoor Liquid Pipe Temperature)
No. Item Details
1
Cooling
Operation
Comp. Frequency Control
To determine the compressor frequency depending on (a),
(b) and (c).
I.U. Electronic Exp. Valve Control
● Quasi PI Control:
To determine the I.U. electronic expansion valve opening
so as to keep (d) at an optimum value.
● To change the I.U. electronic expansion valve opening
when the number of operating indoor units is changed.
O.U. Electronic Exp. Valve Control EVO: 480pls (Fully Opened)
Outdoor Fan Control
To control the fan steps so that High Pressure is within a
stable temperature range.
Reversing Valve Control Reversing Valve: OFF
Control of Solenoid Valve for
High/Low Pressure Bypass (SVA)
At Start-up and when High Pressure Increase Protection
activated: ON
High/Low Pressure Control SVA: ON (during Operation Stop)
2
Heating
Operation
Comp. Frequency Control
● PI Control:
To determine the compressor frequency so as to keep
High Pressure.
● To determine the compressor frequency from (a) and
(c) when heating operation is started or the number of
operating indoor units is changed.
I.U. Electronic Exp. Valve Control
● To determine the I.U. electronic expansion valve opening
so that the indoor liquid pipe temperature (trl) is at an
optimum level.
● To change the I.U. electronic expansion valve opening
when the number of operating indoor units is changed.
O.U. Electronic Exp. Valve Control
● Quasi PI Control:
To determine the O.U. 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 O.U. electronic expansion valve
opening from the compressor frequency ratio before/after
the change and Quasi PI Control.
Outdoor Fan Control
The fan steps are dependent on Ta in the beginning. After
that to control the fan steps so that Pd is within a stable
pressure range.
Reversing Valve Control Reversing Valve: ON
Control of Solenoid Valve for
High/Low Pressure Bypass (SVA)
At Start-up and when High Pressure Increase Protection
activated: ON
High/Low Pressure Control SVA: ON (during operation stop)
3
Defrost
Operation
Comp. Frequency Control Fixed Compressor Frequency
I.U. Electronic Exp. Valve Control
To determine the I.U. electronic expansion valve opening
depending on the temperature at the top of the compressor
(Td).
O.U. Electronic Exp. Valve Control EVO: 480pls (Fully Opened)
Outdoor Fan Control To stop the outdoor fan.
Reversing Valve Control Reversing Valve: OFF
Control of Solenoid Valve for
High/Low Pressure Bypass (SVA)
at Start-up: ON
4 Comp. Preheating Control Crankcase Heater Control
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