110
KHD-S1_ _.R Backup System Wiring Diagram
Function description
Unit start and operating mode (heating/cooling) can be selected by an external signal. e E2 heat exchanger is alternatively
used for heating or cooling of fresh air supplied to the air-conditioned object. e heat potential of the outlet air is always used.
In winter, the outlet air transfers the heat to the E1 heat exchanger. us, heat recovery is achieved. e unit works in heat pump
mode. e valve is without power. Cold inlet air is heated in the E2 heat exchanger (condenser).
In summer, fresh air is cooled as needed in the E2 heat exchanger. e SV valve is energized and the 4-way valve is moved to
the opposite position. e E2 heat exchanger now works as an evaporator. Relatively cold outlet air exhausted from the building
effectively cools the E1 heat exchanger (condenser). Surplus heat is transferred out of the building.
Proper functionality of the system is ensured by the control switchboard (RKJ) with the integrated PLC control system. e
application soware optimises the unit's operation and protects it against overloading. e heat recovery level can be steplessly
controlled (0…10V signal) depending on the inlet air temperature TA (behind the E2 heat exchanger). If the maximum permissible
condensation temperature is reached, the output is automatically reduced. e system is also protected against freezing of the
evaporator by an automatically limited lowest evaporation temperature.
Note: e 4-way valve is displayed in the "cooling" position (SV
without power); the E1 heat-exchanger is in evaporator mode.
Legend:
C1 Cooling compressor
SV1 Power valve
SV 4-way valve
SG Sight glass
EX Expansion valves
E1, 2 Evaporator/condenser
Td, Ts Temperature sensors
Z1-4 Back valves
LP Low-pressure pressostat
HP High-pressure safety pressostat
RKJ Unit power and control distribution board
TA Room temperature
Header
Valve in position
without power
Building wall
Fresh air
Relief air
C1
SV1
SV
HP
(21/28bar)
HPA
LP
(1.7/2.7bar)
LPA
Z3
Z4
Z1
Z2
RKJ
EX1
EX2
T
D
(Cu8 -50)
E1
E2
Filtr
SG
T
A
Faults
Main switch
Filter
0...10 V
Capacity
control
Mode:
Heat/Cool
ON/OFF
Unit
Alarm
4...20 mA
4...20 mA
HP
Comp
Failure
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