LG Multi V Water V ARWM072CAS5 User manual

Outdoor Unit
SERVICE MANUAL
CAUTION
Before Servicing the unit, read the safety precautions in General SVC manual.
Only for authorized service personnel.
R410A
CONFIDENTIAL
Any reproduction, duplication, distribution (including by way of email, facsimile or other electronic means), publication,
modification, copying or transmission of this Service Manual is STRICTLY PROHIBITED unless you have obtained
the prior written consent of the LG Electronics entity from which you received this Service Manual. The material
covered by this prohibition includes, without limitation, any text, graphics or logos in this Service Manual.
Copyright © 2020 LG Electronics Inc. All rights reserved. Only training and service purposes.

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
Air Conditioner Service Manual
TABLE OF CONTENTS
Safety Precautions .....................................................................................................3
Part 1 General Information ........................................................................................8
Part 2 Outdoor units.................................................................................................16
Part 3 HR Units ........................................................................................................44
Part 4 PCB Setting and Test Run ........................................................................... 55
Part 5 Trouble shooting guide................................................................................ 87

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
Safety Precautions
Safety Precautions
To prevent injury to the user or other people and property damage, the following instructions must
be followed.
nIncorrect operation due to ignoring instruction will cause harm or damage. The seriousness is
classified by the following indications.
nMeanings of symbols used in this manual are as shown below.
WARNING
CAUTION
This symbol indicates the possibility of death or serious injury.
This symbol indicates the possibility of injury or damage to properties only.
Be sure not to do.
Be sure to follow the instruction.
WARNING
nInstallation
Have all electric work done by a licensed
electrician according to "Electric Facility
Engineering Standard" and "Interior Wire
Regulations" and the instructions given in
this manual and always use a special circuit.
• If the power source capacity is inadequate or
electric work is performed improperly, electric
shock or fire may result.
Ask the dealer or an authorized technician to
install the air conditioner.
• Improper installation by the user may result in
water leakage, electric shock, or fire.
Always ground the product.
• There is risk of fire or electric shock.
Always intstall a dedicated circuit and breaker.
• Improper wiring or installation may cause fire or
electric shock.
For re-installation of the installed product,
always contact a dealer or an Authorized
Service Center.
• There is risk of fire, electric shock, explosion, or
injury.
Do not install, remove, or re-install the unit
by yourself (customer).
• There is risk of fire, electric shock, explosion, or
injury.

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
Safety Precautions
Do not store or use flammable gas or
combustibles near the air conditioner.
• There is risk of fire or failure of product.
Use the correctly rated breaker or fuse.
• There is risk of fire or electric shock.
Prepare for strong wind or earthquake and
install the unit at the specified place.
• Improper installation may cause the unit to top-
ple and result in injury.
Do not install the product on a defective
installation stand.
• It may cause injury, accident, or damage to the
product.
When installing and moving the air condition-
er to another site, do not charge it with a
different refrigerant from the refrigerant
specified on the unit.
• If a different refrigerant or air is mixed with the
original refrigerant, the refrigerant cycle may
malfunction and the unit may be damaged.
Do not reconstruct to change the settings of
the protection devices.
• If the pressure switch, thermal switch, or other
protection device is shorted and operated
forcibly, or parts other than those specified by
LGE are used, fire or explosion may result.
Ventilate before operating air conditioner
when gas leaked out.
• It may cause explosion, fire, and burn.
Securely install the cover of control box and
the panel.
• If the cover and panel are not installed securely,
dust or water may enter the Outdoor unit and fire
or electric shock may result.
If the air conditioner is installed in a small
room, measures must be taken to prevent the
refrigerant concentration from exceeding the
safety limit when the refrigerant leaks.
• Consult the dealer regarding the appropriate
measures to prevent the safety limit from being
exceeded. Should the refrigerant leak and cause
the safety limit to be exceeded, harzards due to
lack of oxygen in the
room could result
Use a vacuum pump or inert(nitrogen) gas when
doing leakage test or air purge. Do not compress
air or Oxygen and do not use flammable gas es.
Otherwise, it may cause fire or explosion.
• There is the risk of death, injury, fire or explo-
sion.

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
nOperation
Safety Precautions
Do not damage or use an unspecified power cord.
• There is risk of fire, electric shock, explosion, or
injury.
Use a dedicated outlet for this appliance.
• There is risk of fire or electrical shock.
Be cautious that water could not enter the product.
• There is risk of fire, electric shock, or product
damage.
Do not touch the power switch with wet hands.
• There is risk of fire, electric shock, explosion, or
injury.
When the product is soaked (flooded or
submerged), contact an Authorized Service
Center.
• There is risk of fire or electric shock.
Be cautious not to touch the sharp edges
when installing.
• It may cause injury.
Take care to ensure that nobody could step
on or fall onto the Outdoor unit.
• This could result in personal injury and product
damage.
Do not open the inlet grille of the product
during operation. (Do not touch the electro-
static filter, if the unit is so equipped.)
• There is risk of physical injury, electric shock, or
product failure.
CAUTION
nInstallation
Always check for gas (refrigerant) leakage
after installation or repair of product.
• Low refrigerant levels may cause failure of
product.
Do not install the product where the noise or
hot air from the Outdoor unit could damage
the neighborhoods.
• It may cause a problem for your neighbors.
Keep level even when installing the product.
• To avoid vibration or water leakage.
Do not install the unit where combustible gas
may leak.
• If the gas leaks and accumulates around the
unit, an explosion may result.

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
Safety Precautions
Use power cables of sufficient current
carrying capacity and rating.
• Cables that are too small may leak, generate
heat, and cause a fire.
Do not use the product for special purposes,
such as preserving foods, works of art, etc. It
is a consumer air conditioner, not a precision
refrigeration system.
• There is risk of damage or loss of property.
Keep the unit away from children. The heat
exchanger is very sharp.
• It can cause the injury, such as cutting the finger.
Also the damaged fin may result in degradation
of capacity.
When installting the unit in a hospital, com-
munication station, or similar place, provide
sufficient protection against noise.
•
The inverter equipment, private power generator,
high-frequency medical equipment, or radio com-
munication equipment may cause the air condition-
er to operate erroneously, or fail to operate. On the
other hand, the air conditioner may affect such
equipment by creating noise that disturbs medical
treatment or image broadcasting.
Do not install the product where it is exposed to sea wind (salt spray) directly.
• It may cause corrosion on the product. Corrosion, particularly on the condenser and evaporator fins,
could cause product malfunction or inefficient operation.
nOperation
Do not use the air conditioner in special
environments.
• Oil, steam, sulfuric smoke, etc. can significantly
reduce the performance of the air conditioner or
damage its parts.
Do not block the inlet or outlet.
• It may cause failure of appliance or accident.
Make the connections securely so that the
outside force of the cable may not be applied
to the terminals.
• Inadequate connection and fastening may gen-
erate heat and cause a fire.
Be sure the installation area does not deteri-
orate with age.
• If the base collapses, the air conditioner could
fall with it, causing property damage, product
failure, or personal injury.

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
Safety Precautions
Install and insulate the drain hose to ensure
that water is drained away properly based on
the installation manual.
• A bad connection may cause water leakage.
Be very careful about product transportation.
• Only one person should not carry the product if it weighs
more than 20 kg.
• Some products use PP bands for packaging. Do not use any
PP bands for a means of transportation. It is dangerous.
• Do not touch the heat exchanger fins. Doing so may cut
your fingers.
• When transporting the Outdoor unit, suspending it at the
specified positions on the unit base. Also support the
Outdoor unit at four points so that it cannot slip sideways.
Safely dispose of the packing materials.
•
Packing materials, such as nails and other metal or
wooden parts, may cause stabs or other injuries.
• Tear apart and throw away plastic packaging bags
so that children may not play with them. If children
play with a plastic bag which was not torn apart,
they face the risk of suffocation.
Turn on the power at least 6 hours before
starting operation.
• Starting operation immediately after turning on
the main power switch can result in severe
damage to internal parts. Keep the power switch
turned on during the operational season.
Do not touch any of the refrigerant piping
during and after operation.
• It can cause a burn or frostbite.
Do not operate the air conditioner with the
panels or guards removed.
• Rotating, hot, or high-voltage
parts can cause injuries.
Do not directly turn off the main power
switch after stopping operation.
• Wait at least 5 minutes before turning off the
main power switch. Otherwise it may result in
water leakage or other problems.
Auto-addressing should be done in condition of
connecting the power of all indoor and outdoour
units. Auto-addressing should also be done in
case of changing the indoor unit PCB.
Use a firm stool or ladder when cleaning or
maintaining the air conditioner.
• Be careful and avoid personal injury.
Do not insert hands or other objects through
the air inlet or outlet while the air conditioner
is plugged in.
• There are sharp and moving parts that could
cause personal injury.

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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
Part 1
General Information
1. Model Names ..................................................................................9
1.1 Indoor Unit.................................................................................9
1.2 Outdoor unit.............................................................................10
1.3 HR Unit....................................................................................10
2. External Appearance .....................................................................11
2.1 Indoor Unit ...............................................................................11
2.2 Outdoor unit.............................................................................12
3. Combination of Outdoor units .....................................................13
4. Nomenclature.................................................................................14
4.1 Indoor Unit...............................................................................14
4.2 Outdoor unit.............................................................................14
4.3 HR Unit....................................................................................15

Model Names
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Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
1. Model Names
1.1 Indoor Unit
h*Wall Mounted - L : Basic, R : Mirror
*Ceiling Cassette - A : Basic, C : Plasma
*Ceiling Concealed Duct - A : Basic, Z : FAU
Category Chassis
Name
Capacity[Btu/h(kW)]
5.5
(1.6)
7.2
(2.2)
9.6
(2.8)
12.3
(3.6)
15.4
(4.5)
19.1
(5.6)
24.2
(7.1)
28.0
(8.2)
30.0
(8.8)
36.2
(10.6)
42.0
(12.3)
48.1
(14.1)
54.0
(15.8)
76.4
(22.4)
96.5
(28.0)
Wall Mounted
SJ
ARNU053SJ*4 ARNU073SJ*4 ARNU093SJ*4 ARNU123SJ*4 ARNU153SJ*4
SK ARNU183SK*4 ARNU243SK*4
SV ARNU303SVA4 ARNU363SVA4
ART
COOL SF
ARNU093SFA4 ARNU123SFA4
Ceiling
Cassette
1 Way
TU
ARNU073TUC4 ARNU093TUC4 ARNU123TUC4
TT ARNU183TTC4 ARNU243TTC4
2 Way TL ARNU183TLC4 ARNU243TLC4
4 Way
TR
ARNU053TRC4 ARNU073TRC4 ARNU093TRC4 ARNU123TRC4
TQ ARNU153TQC4 ARNU183TQC4
TP ARNU243TPC4 ARNU283TPC4
TN ARNU073TNA4 ARNU093TNA4 ARNU123TNA4 ARNU153TNA4 ARNU183TNA4 ARNU243TNA4 ARNU363TNA4
TM ARNU243TMA4 ARNU283TMA4 ARNU363TMA4 ARNU423TMA4 ARNU483TMA4
Ceiling
Concealed
Duct
High
Static
BH
ARNU073BHA4 ARNU093BHA4 ARNU123BHA4 ARNU153BHA4 ARNU183BHA4 ARNU243BHA4
BG ARNU073BGA4 ARNU093BGA4 ARNU123BGA4 ARNU153BGA4 ARNU183BGA4 ARNU243BGA4 ARNU283BGA4 ARNU363BGA4 ARNU423BGA4
BR ARNU283BRA4 ARNU363BRA4 ARNU423BRA4 ARNU483BR*4 ARNU543BRA4
B8 ARNU363B8A4 ARNU423B8A4 ARNU483B8A4 ARNU763B8*4 ARNU963B8*4
Low
Static
L1
ARNU073L1G4 ARNU093L1G4
L2 ARNU123L2G4 ARNU153L2G4 ARNU183L2G4
L3 ARNU243L3G4
Middle
Static
M2 ARNU073M2A4 ARNU093M2A4 ARNU123M2A4 ARNU153M2A4 ARNU183M2A4 ARNU243M2A4 ARNU283M2A4 ARNU363M2A4 ARNU423M2A4
M3 ARNU283M3A4 ARNU363M3A4 ARNU423M3A4 ARNU483M3A4 ARNU543M3A4
Built
In
B3
ARNU073B3G4 ARNU093B3G4 ARNU123B3G4 ARNU153B3G4
B4 ARNU183B4G4 ARNU243B4G4
Ceiling & Floor VE ARNU093VEA2 ARNU123VEA2
Ceiling Suspended VJ ARNU183VJA2 ARNU243VJA2
Floor
Standing
With
Case
CE
ARNU073CEA4 ARNU093CEA4 ARNU123CEA4 ARNU153CEA4
CF ARNU183CFA4 ARNU243CFA4
Without
Case
CE
ARNU073CEU4 ARNU093CEU4 ARNU123CEU4 ARNU153CEU4
CF ARNU183CFU4 ARNU243CFU4
Vertical AHU
NJ
ARNU123NJA4 ARNU183NJA4 ARNU243NJA4 ARNU303NJA4 ARNU363NJA4
NK ARNU423NKA4 ARNU483NKA4 ARNU543NKA4

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Copyright © 2020 LG Electronics. Inc.
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Model Names
1.2 Outdoor Unit
1.3 HR Unit
Heat Pump ARWM
Heat Recovery
Power Supply 24 HP
(20 Ton)
28 HP
(24 Ton)
34 HP
(28 Ton)
43 HP
(36 Ton)
46 HP
(16 Ton)
54 HP
(48 Ton)
3 Ph, 575 V, 60 Hz 240CAS5 288CAS5 336CAS5 432CAS5 480CAS5 576CAS6
Power Supply 8 HP
(6 Ton)
10 HP
(8 Ton)
12 HP
(10 Ton)
14 HP
(12 Ton)
20 HP
(16 Ton)
3 Ph, 575 V, 60 Hz 072CAS5 096CAS5 121CAS5 144CAS5 192CAS5
Power Supply 2 branches 3 branches 4 branches
1 Ph, 208/230 V, 60 Hz PRHR022A PRHR032A PRHR042A
Power Supply 2 branches 3 branches 4 branches
1 Ph, 220-240 V, 50 Hz / 1 Ph, 220 V, 60 Hz PRHR023 PRHR033 PRHR043
1 Ph, 208/230 V, 60 Hz PRHR023A PRHR033A PRHR043A
Power Supply 6 branches 8 branches
1 Ph, 220-240 V, 50 Hz / 1 Ph, 220 V, 60 Hz PRHR063 PRHR083
1 Ph, 208/230 V, 60 Hz PRHR063A PRHR083A

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Copyright © 2020 LG Electronics. Inc.
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External Appearance
2. External Appearance
2.1 Indoor Unit
Wall Mounted
ART COOL
Ceiling Cassette- 1Way
Ceiling Cassette- 4Way
Ceiling & Floor
Ceiling Suspended
ARNU073TUC4
ARNU093TUC4
ARNU123TUC4
ARNU183TTC4
ARNU243TTC4
Ceiling Cassette -2Way
ARNU183TLC4
ARNU243TLC4
ARNU053TRC4
ARNU073TRC4
ARNU093TRC4
ARNU123TRC4
ARNU153TQC4
ARNU183TQC4
ARNU073TNA4
ARNU093TNA4
ARNU123TNA4
ARNU153TNA4
ARNU183TNA4
ARNU243TNA4
ARNU363TNC4
ARNU243TPC4
ARNU283TPC4
ARNU243TMA4
ARNU283TMA4
ARNU363TMA4
ARNU423TMC4
ARNU483TMC4
Ceiling Concealed Duct – Middle Static
ARNU073M2A4
ARNU093M2A4
ARNU123M2A4
ARNU153M2A4
ARNU183M2A4
ARNU243M2A4
ARNU283M2A4
ARNU363M2A4
ARNU423M2A4
ARNU283M3A4
ARNU363M3A4
ARNU423M3A4
ARNU483M3A4
ARNU543M3A4
Ceiling Concealed Duct - Low Static
ARNU073L1G4
ARNU093L1G4
ARNU123L2G4
ARNU153L2G4
ARNU183L2G4
ARNU243L3G4
ARNU053SJ*4
ARNU073SJ*4
ARNU093SJ*4
ARNU123SJ*4
ARNU153SJ*4
ARNU183SK*4
ARNU243SK*4
ARNU303SVA4
ARNU363SVA4
ARNU093SFA4
ARNU123SFA4
ARNU093VEA2
ARNU123VEA2
URNU183VJA2
URNU243VJA2
Floor Standing
With case
ARNU073CEA4
ARNU093CEA4
ARNU123CEA4
ARNU153CEA4
ARNU183CFA4
ARNU243CFA4
Without case
ARNU073CEU4
ARNU093CEU4
ARNU123CEU4
ARNU153CEU4
ARNU183CFU4
ARNU243CFU4
Vertical AHU
ARNU123NJA4
ARNU183NJA4
ARNU243NJA4
ARNU303NJA4
ARNU363NJA4
ARNU423NKA4
ARNU483NKA4
ARNU543NKA4
Ceiling Concealed Duct - High Static
ARNU363B8A4
ARNU423B8A4
ARNU483B8A4
ARNU763B8*4
ARNU963B8*4
Ceiling Concealed Duct – Built-in
ARNU073B3G4
ARNU093B3G4
ARNU123B3G4
ARNU153B3G4
ARNU183B4G4
ARNU243B4G4
* L : Basic, R : Mirror
* A:Basic, C:Plasma
* A : Basic, Z : FAU

External Appearance
- 12 -
Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
2.2 Outdoor unit
2.2.1 Heat Recovery & Heat Pump
Chassis Model Name Model
UWB
ARWM072CAS5
ARWM096CAS5
ARWM121CAS5
ARWM144CAS5
ARWM192CAS5
UWB
UWB
ARWM240CAS5
ARWM288CAS5
ARWM336CAS5
UWB
UWB
UWB
ARWM432CAS5
ARWM480CAS5
ARWM576CAS5

Combination of Outdoor units
- 13 -
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3. Combination of Outdoor Units
3.1 Heat Recovery & Heat Pump
• The biggest module should be master module and others are slaves.
• Setting method of master/slave and position of master in the system is explained in the installation chapter.
Model Name HP Ton Number
of Units
Module (Ton)
6 8 10 12 16
ARWM072CAS5 8611
ARWM096CAS5 10 8 1 1
ARWM121CAS5 12 10 1 1
ARWM144CAS5 14 12 1 1
ARWM192CAS5 20 16 1 1
ARWM240CAS5 24 20 2 2
ARWM288CAS5 28 24 2 1 1
ARWM336CAS5 34 28 2 1 1
ARWM432CAS5 43 36 3 3
ARWM480CAS5 46 40 3 2 1
ARWM576CAS5 54 48 3 3

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Copyright © 2020 LG Electronics. Inc.
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Nomenclature
4. Nomenclature
4.1 Indoor Unit
4.2 Outdoor unit
ARN U 307 ATJ 4
Generation
Chassis Name
Electrical Ratings
1 : 1 Ph, 115 V, 60 Hz 2: 1 Ph, 220 V, 60 Hz
6 : 1 Ph, 220 - 240 V, 50 Hz 7: 1 Ph, 100 V, 50/60 Hz
3 : 1 Ph, 208/230 V, 60 Hz
Total Cooling Capacity in Btu/h Class
EX) 18,000 Btu/h Class '18'
Combination of Inverter Type and
Cooling Only or Heat Pump
N: AC Inverter and H/P V: AC Inverter and C/O
U: DC Inverter and H/P and C/O
System with
Indoor Unit using R410A
LGETA:U Ex) URN
Combinations of functions
A: Basic function
L: Neo Plasma(Wall Mounted)
C:Plasma(Ceiling Cassette)
G: Low Static
U: Floor Standing without Case
ART COOL Type Panel Color
B:Blue R:Mirror V: Silver
Serial Number
A: Basic Function
Indicates that this is Water System
Outside Unit using the R410A
Combination of Inverter Type and
for both Heat Pump and Heat Recovery
M : for both Heat Pump and Heat Recovery
ARW M C072 AS5
Primary. Main Fuction
S : Standard
E : High Efficiency
Secondary. Usage Embient
H : High Ambient
C : Cold Area
R : Anti-Corosion
Electrical Ratings
B : 3 Ph. 208 V/230 V, 60 Hz
C : 3 Ph. 575 V, 60 Hz
D : 3 Ph. 460 V, 60 Hz
Total Cooling Capacity in Btu/h
EX) 72,000 Btu/h Class →'072'
※ Heat recovery ventilator refer to the DX-Coil manual

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Nomenclature
Copyright © 2020 LG Electronics. Inc.
All right reserved. Only for training and service purposes
4.3 HR Unit
Serial Number
No. of Connected branches
02 : For 2 branches
03 : For 3 branches
04 : For 4 branches
06 : For 6 branches
08 : For 8 branches
Indicates that this is System
HR Unit using the R410A
PRHR 04 3 A
※ These are model names of the basic function.

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Part 2
Outdoor units

- 17 -
Copyright © 2020 LG Electronics. Inc.
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Function
Function
1. Basic control ...................................................................................................................18
1.1 Normal operation .......................................................................................................18
1.2 Compressor control....................................................................................................18
1.3 Master and slave unit's EEV control ..........................................................................19
2. Special control ................................................................................................................20
2.1 Oil return control ........................................................................................................20
2.2 Stop operation............................................................................................................22
3. Protection control ...........................................................................................................23
3.1 Pressure protection control ........................................................................................23
3.2 Discharge temperature control...................................................................................24
3.3 Inverter protection control ..........................................................................................24
4. Other control ...................................................................................................................25
4.1 Initial setup.................................................................................................................25
4.2 Cool & Heat selector .................................................................................................29
4.3 Outdoor unit address ................................................................................................30
4.4 IDU capacity adjusting ...............................................................................................31
4.5 Target pressure adjusting...........................................................................................32
4.6 Geothermal mode ......................................................................................................33
4.7 220 V out for solenoid valve.......................................................................................34
4.8 Variable water flow control .........................................................................................35
4.9 Pump out....................................................................................................................36
4.10 Vacuum Mode ..........................................................................................................39
4.11 Back up ....................................................................................................................40
4.12 Forced oil return.......................................................................................................41
4.13 Cycle Data View.......................................................................................................42
4.14 Refrigerant noise reduction mode............................................................................43

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Function
1.2 Compressor control
Fuzzy control : Maintain evaporating temperature(Te) to be constant on cooling mode and condensing tem-
perature(Tc) on heating mode by Fuzzy control to ensure the stable system performance.
[TC:47~51°C(116.6~123.8°F), Te:2~5°C(35.6~41°F)]
(1) Cooling mode
Te can be set various step at installation mode.
(2) Heating mode
Tc can be set various step at installation mode.
Note: By setting dip switch, Te and Tc are decided simultaneously.
1.1 Normal operation
1. Basic control
Fuzzy Control
Stop(0Hz)
Min. frequency
Fuzzy control start
Target
Inverter linear control as cooling and heating load increasing
System Capacity
Cooling and heating load
(Linear Control)
(Linear Control)
(Linear Control)
Inverter
Comp 2
Inverter
Comp 1
Inverter
Comp 2
Inverter
Comp 3
Inverter
Comp 1
Inverter
Comp 2
Inverter
Comp 3
Inverter
Comp 4
Inverter
Comp 1
Actuator Cooling operation Heating operation Stop state
Compressor Fuzzy control Fuzzy control stop
Main EEV Full open Fuzzy control Min. pulse
Subcooling EEV Fuzzy control • Avoiding control of high discharge temperature
• Fuzzy control Min. pulse
Indoor Unit EEV Superheat fuzzy control Subcooling fuzzy control Min. pulse

- 19 -
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Function
1.3 Master and slave Unit's EEV control
(1) Main EEV control
Main EEV operates with fuzzy control rules to keep the degree of super Heat(Superheat) (about 3°C or
6°F)at the evaporator outlet stable during heating mode
The degree of Superheat = Tsuction - Tevaporation
Tsuction : temperature at suction pipe sensor(°C,°F)
Tevaporation : evaporation temperature equivalent to low pressure(°C,°F)
(2) Subcooling EEV control(about 15°C or 30°F)
Subcooling EEV works with fuzzy rules to keep the degree of Subcool at the outlet of subcooler during
cooling mode
The degree of Subcool = Tcondensation - Tliquid
Tliquid : temperature at outlet of subcooler(°C,°F)
Tcondensation : condensation temperature equivalent to high pressure(°C,°F)
(3) Avoiding excessive high discharge temperature : when main EEV opens some given opening (R410A :
800 pls) and discharge temperature is above 85°C(185°F) in heating operation, subcooling EEV may con-
trol the "subcooling out temperature-evaporating temperature" to be some given difference.

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Function
2.1 Oil return control
2.1.1 Oil return control on cooling mode
Oil return operation recovers Oil level in compressor by collecting oil accumulated in pipe.
Each cycle component operates as shown on the below table during oil return operation.
• Oil return operation time : 3 min for running step
• Starting condition : When low oil level which is measured by oil level sensor is kept continuously then oil return
operation will be start.
• Oil return process ends if compressor protection control starts
2. Special control
Outdoor unit
Indoor Unit
Component Starting Running Ending
Fan Normal control OFF Normal control
Thermo on unit EEV Normal control Normal control Normal control
Thermo off unit EEV 40 pulse 400 pulse 80 pulse
Oil return signal OFF ON OFF
Component Starting Running Ending
Inv Compressor 30 Hz Setting Value 30 Hz
Main EEV Max. pulse Max. pulse Normal control
Subcooling EEV Min. pulse 20 pulse 80 pulse
4way valve 1 OFF OFF OFF
4way valve 2 Heat Recovery : OFF
Heat pump : ON OFF OFF