System Description; System Overview - Hitachi DXF-2.0A1 Operation Installation Maintenance Manual

2 System Description
DX-Kit is specially designed to allow connection of direct expansion coils (DX coil) in a field-supplied Air
Handling Unit (AHU) to INVERTER-DRIVEN MULTI-SPLIT SYSTEM AIR CONDITIONERS outdoor units for
cooling and heating applications.
● Select an appropriate AHU with appropriate specifications and compatibility with regulations. Match with
right DX-Kit and outdoor units, if not the performance, operation reliability and Lifetime of entire AHU
system may be influenced.
● The temperature of the heat exchanger inside the AHU may become down to -20°C and the discharge air
temperature may become 0°C during cooling operation. The components and materials inside the AHU
shall be compatible with the temperature. Note that dew condensation on the heat exchanger, AHU main
body and the refrigerant pipe occurs. Drain and insulate the AHU and pipe properly.
● The temperature of the heat exchanger inside the AHU may become up to 120°C and the discharge air
temperature may become 60°C during heating operation. The components and materials inside the AHU
shall be compatible with the temperature.
● The performance may not reach due to outside temperature limitation and protection for outdoor units.
● Interlock the AHU with the system to protect the equipment when the system error occurs.
2.1

System Overview

DX-Kit is composed of Control Box for system control with PCB and all the electronic stuff, and Expansion
Valve Box for refrigerant cycle control in which an electrical expansion valve is located. The following figure
shows an installation example for the system.
● The installation distance between the DX-Kit and the AHU must be as short as possible.
● The distance between the unit or device with heat exchanger and the expansion valve box for the
piping length must be 5m or less. Be certain the elevation difference between the unit or device
with heat exchanger and the expansion valve box does not exceed 2m.
● Installation distance between the control box and the unit or device with heat exchanger must be
short enough so that the thermistors sensing are not distorted.
● The thermistor cable must not be installed in the same ducting as power or control cables.
Capacity
Ratio W2
Capacity
Ratio W1
P5417151-rev.1
Ti
Multi combination with AHU and standard indoor unit
Fig.2.1 System Overview (1)
5