ESIE15-11A
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Part 1. Introduction
3. General operation of VRV heat recovery system
23/09/16
Page 9
VRV4 indoor units
3. General operation of VRV heat recovery system
•
When indoor unit is selecting heating mode, discharge gas is supplied by the outdoor unit(s) into the dual pressure line through
EVH (high pressure expansion valve) fully opened in the BS unit to the indoor unit.
•
When indoor unit is selecting cooling mode, suction gas returns from indoor unit gas line through EVL (low pressure expansion
valve) fully opened in the BS unit to the outdoor unit.
•
Indoor unit in cooling controls the indoor expansion valve on suction superheat (SH) by comparing gas and coil sensor on
indoor unit.
•
Indoor unit in heating controls the indoor expansion valve on liquid sub-cool (SC) by comparing Tc (outdoor condensing
temperature) derived from reading of high pressure sensor, and indoor coil temperature.
•
When indoor unit requires change over between cooling and heating, the switching between suction and discharge line is
performed only in the BS unit that received the request of indoor unit to change over. Change over sequence is explained in
“General built up VRV4 BS unit”.
•
Outdoor can switch outdoor heat exchanger separately condenser/evaporator in function of unbalance between cooling and
heating demand indoor side.
“SC”
4 way valve
Receiver
“SH”
off
“Tc”
Pc
D
Tc
HP sensor
LP sensor
Closed
Compressor
on
off
EVL
EVH
Expansion
valve
Suction
accumulator
BS unit -
cooling
BS unit -
heating
VRV indoor heating
VRV indoor cooling
Fully open
Superheat
Sub-cool
Fan
motor
VRV outdoor
“SH” & “Te”
Pe
D
Te
