Mitsubishi Electric AT-50B User manual

Before using the controller, read this
Instruction Book carefully to ensure
proper operation.
Retain this Instruction Book for future
reference.
Make sure that this manual as well as the
Installation Manual are passed on to any
future air condition system users.
To ensure safety and proper operation of
the unit, the unit should only be installed
by qualified personnel.
<ORIGINAL>
Air-conditioner Control System
Advanced Touch Controller
MODEL
AT-50B
Instruction Book
Safety Precautions .............................................................. 2
Function List ........................................................................ 4
Names and Functions of Controller Components................ 6
Screen Conguration [HOME screen] ................................. 8
Buttons [HOME screen]..................................................... 10
Icon Displays [HOME screen]............................................ 12
Basic Operations ............................................................... 16
Screen selection......................................................................... 16
Group selection .......................................................................... 17
Operation Screen (GROUP screen)........................................... 18
Operating the Air conditioning unit group • Air To Water (PWFY) group .... 18
ON/OFF operation........................................................................ 18
Mode............................................................................................. 18
Temperature setting...................................................................... 21
Interlocked ventilation units(LOSSNAY)/Fan speed/Air direction/Louver settings ....... 23
Disable-Scheduled-Operation button ........................................... 24
Operating the LOSSNAY group.................................................. 24
Mode............................................................................................. 24
Fan speed setting......................................................................... 24
Operating the general equipment group..................................... 24
ON/OFF operation........................................................................ 24
Multiple group selection screen.................................................. 25
Disabling functions ..................................................................... 25
Menu Screen ..................................................................... 26
Usage - Main Menu Settings ............................................. 28
Operation Setting ....................................................................... 28
Restriction Settings .................................................................... 44
Control Panel.............................................................................. 52
System Management ................................................................. 59
Maintenance...................................................................... 64
Touch Panel Cleaning screen..................................................... 64
Troubleshooting................................................................. 65

2
Safety Precautions
Indicates a risk of death or serious injury.
●Thoroughly read the following safety precautions prior to installation.
●Observe the following precautions to ensure safety.
Indicates a risk of serious injury or structural damage.
WARNING
CAUTION
●After reading this manual, pass it on to the end user to retain for future reference.
●Keep this manual for future reference and refer to it as necessary. This manual should be made available to those who repair or relocate
the controller. Make sure that the manual is passed on to any future AT-50B users.
All electric work must be performed by qualied personnel.
General precautions
(Prohibited actions) (Do not touch) (No water) (No wet hands) (Electric shock hazards) (Injury hazards) (Important actions)
WARNING
Do not install the unit in a place where large amounts
of oil, steam, organic solvents, or corrosive gases,
such as sulfuric gas, are present or where acidic/
alkaline solutions or sprays are used frequently.
These substances can compromise the performance
of the unit or cause certain components of the
unit to corrode, which can result in electric shock,
malfunctions, smoke, or re.
To reduce the risk of shorting, current leakage,
electric shock, malfunctions, smoke, or re, do not
wash the controller with water or any other liquid.
To reduce the risk of electric shock, malfunctions,
smoke or re, do not operate the switches/buttons or
touch other electrical parts with wet hands.
To reduce the risk of re or explosion, do not place
ammable materials or use ammable sprays around
the controller.
CAUTION
To reduce the risk of damage to the controller, do not
directly spray insecticide or other ammable sprays
on the controller.
To reduce the risk of electric shock or malfunctions,
do not touch the touch panel, switches, or buttons
with a pointy or sharp object.
Precautions during installation
WARNING
Do not install the controller where there is a risk of
leaking ammable gas.
If ammable gas accumulates around the controller, it
may ignite and cause a re or explosion.
Properly dispose of the packing materials. Plastic
bags pose suffocation hazard to children.
To reduce the risk of injury or electric shock, before
spraying a chemical around the controller, stop the
operation and cover the controller.
To reduce the risk of injury or electric shock, stop
the operation and switch off the power supply before
cleaning, maintaining, or inspecting the controller.
Properly install all required covers to keep moisture
and dust out of the controller. Dust accumulation and
water can cause electric shock, smoke, or re.
To reduce the risk of injury and electric shock, avoid
contact with sharp edges of certain parts.
To avoid injury from broken glass, do not apply
excessive force on the glass parts.
To reduce the risk of injury, wear protective gear
when working on the controller.
●Nomenclature

33
Precautions for moving or repairing the controller
WARNING CAUTION
The controller should be repaired or moved only by
qualied personnel. Do not disassemble or modify the
controller.
Improper installation or repair may cause injury,
electric shock, or re.
To reduce the risk of shorting, electric shock, re,
or malfunction, do not touch the circuit board with
tools or with your hands, and do not allow dust to
accumulate on the circuit board.
Additional precautions
To avoid damage to the controller, use appropriate tools to
install, inspect, or repair the controller.
AT-50B is designed for exclusive use with the Building
Management System by Mitsubishi Electric. The use of this
controller for with other systems or for other purposes may
cause malfunctions.
To avoid damage to the controller, do not overtighten the
screws.
To avoid discoloration, do not use benzene, thinner, or
chemical rag to clean the controller. To clean the controller,
wipe with a soft cloth soaked in mild detergent that is diluted
with an appropriate amount of water, and wipe down with a
wet cloth followed by a dry cloth. Do not use the detergent
straight.
To avoid damage to the controller, provide protection against
static electricity.
If the supply cord is damaged, it must be replaced by the
manufacturer, its service agent or similarly qualied persons
in order to avoid a hazard.
This appliance is not intended for use by persons (including
children) with reduced physical, sensory or mental
capabilities, or lack of experience and knowledge, unless
they have been given supervision or instruction concerning
use of the appliance by a person responsible for their safety.
Children should be supervised to ensure that they do not
play with the appliance.
This appliance is intended to be used by expert or trained
users in shops, in light industry and on farms, or for
commercial use by lay persons.

4
Function List
The table below summarizes the functions that are available on the AT-50B.
Refer to the pages listed for details.
Function Description Page
Unit Operation
ON/OFF operation
Switches the ON/OFF operation of the units such as air conditioning
units. The LED on the Collective ON/OFF button will light up when one
or more units are in operation and off when all units are stopped.
18
Mode
Switches the mode as follows for each group or all groups.
Air conditioning unit group: Cool/Dry/Fan/Auto/Heat
LOSSNAY group: Bypass/Heat recovery/Auto
Air To Water (PWFY) group: Heating/Heating ECO/Hot Water/
Anti-freeze/Cooling
18
Set Temperature Sets the set temperature for each group or all groups. 21
Fan Speed Adjusts the fan speed for each group or all groups. 23
Air Direction Adjusts the air direction for each group or all groups. 23
Louver Enables/disables the louver for each group or all groups. 23
ON/OFF operation
for interlocked
ventilation
The ON/OFF operation of the interlocked ventilation unit is interlocked
with the ON/OFF operation of the air conditioning unit. The interlocked
ventilation units can be independently operated for ON (High/Low)/OFF
for each group or all groups. (When the ventilation unit is interlocked
with the air conditioning unit, the ventilation mode cannot be used.)
23
Collective Operation The following functions can be collectively executed on multiple groups:
Setback, Schedule, Mode, Temperature Correction, RC Prohibition.
20
40
Time and
Schedule
Date and Time Sets the date, time, and display formats. The current time will appear at
the top right corner of the HOME screen. 28
Weekly/One-day
schedule
• Allows the user to set the weekly schedule for each group.
• Maximum of 16 events can be scheduled for each day.
• The types of actions that can be scheduled are as follows: ON/OFF,
Mode, Set Temperature, Fan Speed, Air Direction, and Prohibit
Remote Controller Operation.
• Maximum of 12 patterns can be congured for the weekly schedule,
and 5 for one-day schedule.
• Two types of weekly schedules (Summer/Winter) can be set.
• One-day schedule overrides the weekly schedule.
30
Setback Control
This function helps keep the indoor temperature in the
temperature range while the units are stopped and during the
time this function is effective.
37
Disabling scheduled
operation
Scheduled operation can be temporarily disabled.
This setting must be set to OFF to run scheduled operation. 24
System
Management System-Changeover
Automatically switches the entire system (all indoor units that are
connected to the same outdoor units) to cooling or heating by
periodically monitoring the room temperature and the preset temperature
of each group and determining the best operation mode.
• The System-Changeover function is not available for the following
types of products: Simultaneous cooling/heating units (with automatic
mode change function), Mr. SLIM®, LOSSNAY, and DIDO controller.
61
*1: Available functions vary depending on the unit type. Only the functions that are supported by the connected units can
be controlled from the AT-50B.
*1
*1
*1
*1
*1
*1

5
Function Description Page
Restriction
Settings
Lock Buttons
Locks the following buttons: Collective ON/OFF, F1, F2, and Main
Menu screen buttons.
Locks the following functions: ON/OFF, Mode, Set Temperature,
Fan Speed, and Schedule ON/OFF.
11
25
44
Set Temperature
Range Limit
Limits the available temperature range for the local remote
controllers (each group or all groups). 46
Prohibit Remote
Controller
Prohibits access to the ON/OFF, Mode, Set Temperature,
Maintenance Sign Reset, Air Direction, and Fan Speed settings
from the local remote controllers, and also deactivates Timer
(Schedule) settings from the local remote controllers (collectively or
by group).
48
Operation Mode
Selection Limit
When set as the main controller, operation of the following modes
with the local remote controllers can be prohibited.
No Cooling Operation: Cool, Dry, and Auto cannot be chosen.
No Heating Operation: Heat and Auto cannot be chosen.
No Heating/Cooling: Cool, Dry, Heat, and Auto cannot be chosen.
50
Basic Settings
Display Format
Selects the display formats for the following items: Display
language, temperature unit, room temperature, display or non-
display of Cool/Heat mode icons (during Auto mode), backlight
timer, and group names.
52
Function Key Setting
The F1 button and the F2 button can be set as a run button of
the following collective operation: Setback, Schedule, Mode,
Temperature Correction, Remote Controller Prohibition.
56
HOME screen
Group Icon Setting
When the group icon is touched, the action differs depending on
the group icon setting. Default is set to the Group icon setting 2.
Group icon setting 1:
Turns ON/OFF the units in the group whose
group icon is touched.
Group icon setting 2:
Displays the check mark when group icon is
touched. Touch the group icons of the groups
to be operated, and then touch the “Operate”
button to move to the GROUP screen. Multiple
groups can be selected. Use this mode when
operating the multiple groups collectively.
Group icon setting 3: Directly moves to the GROUP screen of the
group whose group icon is touched.
43
Volume Control Sets the sound volume and screen brightness. 57
Maintenance
Error
If an error occurs on the AT-50B controller or the units and
controllers it controls, the LED on the Collective ON/OFF button
will blink. If an error occurs on the indoor or LOSSNAY units, will
appear on the corresponding group icon on the HOME screen. The
error code can be veried and reset on the Status List screen.
59
Maintenance Sign Filter icon will appear on the HOME screen when the lter is due
for cleaning. The icon can be removed from the Status List screen. 60
Touch Panel
Cleaning mode Disables the touch panel to allow the user to clean the panel. 64
Touch Panel
Calibration mode
Calibrates the touch panel if the touch panel does not respond
correctly when touched. 58
Miscellaneous
External input
Receives input signals from external devices and start/stop all
groups of units or permit/prohibit operations from the local remote
controllers. Requires cable connections.
External output
Outputs the operation status of the units (ON/OFF) or error signals
to external devices collectively, using contact signals. Requires
cable connections.

6
Names and Functions of Controller Components
Product features
3
12
4
5
The AT-50B described in this manual is a centralized controller with color LCD touch panel for air
conditioning units, LOSSNAY, Air To Water (PWFY)*, and general equipment using the Mitsubishi Electric
DIDO controller (PAC-YG66DCA).
AT-50B can control up to 50 units/50 groups. *1
AT-50B controls and monitors the air conditioning units of each group. AT-50B also can control detailed
scheduling and prohibits the local remote controller operation in each room (group), which may lead to
energy savings.
Basic operations are accessed through the AT-50B touch panel. ON/OFF, F1, and F2 operations that
control air conditioning units collectively are accessed by using buttons next to the touch panel.
AT-50B display screen consists of three types, corresponding to the usage.
HOME screen : Monitoring screen to monitor the operation status of the units
(described in this Instruction Book)
Main Menu screen : Setting screen to set the functions such as schedule settings
(described in this Instruction Book)
Maintenance screen : Initial setting screen to set the basic systems such as group settings
(described in the Installation Manual)
* 1 Group: minimum unit to be controlled by AT-50B
A group consists of units (16 units maximum).
* “Booster unit” and “Water HEX unit” are referred to as “Air To Water (PWFY)”.
* AHC (Advanced HVAC CONTROLLER) cannot be controlled from AT-50B.
Buttons 2, 3, and 4have indicators on the top.

7
2 Collective ON/OFF button *1
The Collective ON/OFF button enables the collective ON/OFF function that allows the user to
turn on/off the air conditioning units, LOSSNAY, DIDO controllers, and Air To Water (PWFY) units
in all groups collectively.
The indicator corresponds to the operation status of controlled units.
Unlit : Indicates that all units are stopped.
Lit : Indicates that one or more units are in operation.
Blink : Indicates that an error is occurring.
AT-50B features a 5" color LCD touch panel. Touch panel displays the operation status of the
units. Function settings such as week schedule settings are accessed through the touch panel.
The backlight lights up when the panel is touched, and lights off after certain period of time. The
backlight will remain lit as long as an error exists.
1Display/Touch panel
3 Function 1 button (F1), 4Function 2 button (F2) *1 *2
Desired functions from the following list can be assigned to the F1 and F2 buttons.
(Setback/Schedule/Mode/Temperature Correction/Remote Controller Prohibition)
The functions to assign to these buttons can be selected from the Function Key Setting on the
Control Panel.
The indicator on the buttons indicates the enabled/disabled status of the function.
Unlit : The assigned function is disabled.
Lit : The assigned function is enabled.
The indicators on the F1 and F2 buttons will be lit or unlit when the functions that are assigned to
the F1 and F2 buttons are enabled or disabled from the Collective Operation panel.
5Power indicator
The power indicator lights up when the power to AT-50B is turned on.
Unlit : Power OFF
Lit : Power ON
Touch panel/Buttons
*1 When the button is pressed while the operation is prohibited, the LED will blink twice.
*2 Buttons 2, 3, and 4 are available only on the HOME screen.

8
Screen Configuration [HOME screen]
1. How to switch the HOME screen
Touch tabs to change the display format.
2. How to move to the Main Menu screen
3. How to move to the Maintenance screen
Refer to the Installation Manual.
: Displays the GRID screen.
: Displays the GRID (zoom-out) screen.
: Displays the GRID (zoom-in) screen.
: Displays the LIST screen.
: Displays the GROUP screen.
: Displays the Main Menu screen.
GRID screen
Zoom-out screen
To the GRID
(zoom-in) screen
To the GRID
(zoom-out) screen
Zoom-in screen

9
HOME screen
To the GROUP screen
To the GRID screen
To the LIST screen
To the GRID screen
To the Main Menu screen
To the HOME screen
GROUP screen
To the LIST
screen
To the GROUP
screen
LIST screen
[Main Menu screen]

10
Buttons [HOME screen]
①②③󱦯④⑤
⑨⑩⑦⑧ ⑧⑪
⑯⑰⑱
⑮
󱦱
⑥
⑥
󱦱
⑪
⑫
⑥
⑭
⑬
⑳
⑲
HOME screen
GRID (zoom-out) screen GRID (zoom-in) screen
Displays the operation status of all groups.
The button layout 6varies with the number of the
registered groups.
Displays the detailed operation status of each
group. (10 groups on 5 pages maximum)
LIST screen GROUP screen
Displays the detailed operation status of each
group with group name. (5 groups on 10 pages
maximum)
Displays the detailed operation status of each
group. Sets group operations.
(When the air conditioning units or Air To Water
(PWFY) units are controlled)
Note: Display ⑨and ⑩vary depending on the Group icon
setting. Refer to P17 “Group icon setting” for details.
Sample displays above are for default setting: Group
icon setting 2.
Group icon setting 1
Group icon setting 2
Group icon setting 3
LOSSNAY
Air conditioning units
Auto (dual set point)
mode

11
Note: Depending on the units to be controlled and AT-50B settings, available button operations and displays vary.
: While the icon is displayed on the button, the operation is locked.
Flips through pages.
aPage button
Switches the group to be displayed.
cGroup-switching button
Displays the GRID screen.
1GRID screen button
Displays the LIST screen.
2LIST screen button
Displays the GROUP screen.
3GROUP screen button
Displays the Main Menu screen.
4Main Menu screen button
Press this button to bring up the Collective Operation
panel.
(Refer to P20 for information about the Collective
Operation panel.)
7 Access-the-Collective-Operation
-panel button
Selects/Deselects groups collectively. Adds check
marks to all selected icons.
9Select-All button
Moves to the GROUP screen of the selected group.
Moves to the multiple group selection screen when
multiple groups are selected. Refer to P25 “Multiple
group selection screen” for details.
0Move-to-the-selected-group button
Shows/Hides the display for the information below.
• Set temperature
• Scheduled operation is enabled.
bDisplay selection button
Switches the operation mode of the air conditioning
units, LOSSNAY, and Air To Water (PWFY) units.
dMode button
Adjusts the set temperature by using the + and –
buttons. Set temperature appears above the button.
eSet temperature button
Use this button to temporarily disable the scheduled
operation on the display. The indicator on the button
will remain lit when the function is enabled.
The scheduled operation will not be run when the icon
is displayed.
f Disable-Scheduled-Operation button
Displays the popup window of interlocked
ventilation (LOSSNAY)/air direction/fan speed/
louver setting screen.
* Refer to P23 “Interlocked ventilation units (LOSSNAY)/Fan
speed/Air direction/Louver settings” for the popup window.
g Interlocked ventilation (LOSSNAY)/Air
direction/Fan speed/Louver setting button
Operation differs depending on the group icon setting.
Group icon setting 1
Turns ON/OFF the units in the group whose group
icon is touched.
Group icon setting 2
Switches the group icon between Selected
(checked) and Deselected (unchecked).
(Default) Displays the check mark when group icon
is touched.
Group icon setting 3
Directly moves to the GROUP screen of the group
whose group icon is touched.
6 Group icon (operation status display) button
Changes the operation to ON/OFF.
⑱ON/OFF button
Switches LOSSNAY fan speed between Low and High.
⑳Fan speed selection button
Displays the current time.
1Current time
Displays the current page/total page number.
2Current page/Total pages
Locks or unlocks the buttons on the AT-50B.
Press and hold the button for two seconds to lock or
unlock the buttons.
The locked/unlocked status icon will appear on the
buttons.
5Operation lock button
Locked Unlocked
A password may be required to unlock certain buttons.
Select the buttons to be locked from the Lock Buttons
(Refer to P44.) on the Main Menu.
If no items have been selected, the operation lock
button will not appear on the screen.
: Displays the zoom-out screen.
: Displays the zoom-in screen.
8 GRID (zoom-out/zoom-in) screen button
When the cooling and heating set temperatures are displayed
above the button, touching the button will display the popup
window to adjust the set temperatures for the Auto (dual set
point) mode. Refer to P21 “Temperature setting” for details.
⑲ Set temperature button (Auto (dual set point) mode)

12
Icon Displays [HOME screen]
(1) GRID (zoom-out) screen
(2) GRID (zoom-in) screen
[ON (BG Color: blue)]
Group No. •Check Water sign**:
•Filter sign*
•Check mark
[OFF (BG Color: black)] [Error (BG Color: yellow)]
Error display
Communication error
at startup
[Air conditioning unit group]
[ON (BG Color: blue)]
•Check mark
•ON/OFF operation
prohibition
Group No.
•Mode
•Filter sign:
Schedule (enable/disable)
Room temperature
Interlocked ventilation
(LOSSNAY) operation
[OFF (BG Color: black)]
[OFF (BG Color: black)][ON (BG Color: blue)]
[General equipment group]
Schedule (enable/disable)
General equipment icon
[Error (BG Color: yellow)]
[Air conditioning unit/LOSSNAY/
General equipment group]
Error display
Error:
Displays when an error occurs.
Startup (communication) error:
Displays as well as the error display when
a startup (communication) error occurs.
Filter sign:
Displays when lter needs maintenance.
During scheduled operation:
Displays .
When the Disable-Scheduled-Operation button is enabled
or Timer (Schedule) execution is prohibited
: Displays .
Room temperature:
Displays the current room temperature. The displayed
temperature will blink when the room temperature is at or
above 40 ºC (104 ºF) (39 ºC (102 ºF) on some models), or
at or below 0 ºC (32 ºF) (8 ºC (46 ºF) on some models).
*Temperatures will be displayed in 1 ºC increments on the
GRID (Zoom-in) screen and on the LIST screen, even if the
temperature is set to appear in 0.5 ºC increments.
* For Air conditioning units
** For Air To Water (PWFY) units
[LOSSNAY group]
[ON (BG Color: blue)] [OFF (BG Color: black)]
Filter sign:
LOSSNAY icon
Schedule (enable/disable)
[Air To Water (PWFY) group]
•Check mark
•ON/OFF operation
prohibition
Group No.
•Mode
•Check Water sign:
Water temperature
Air To Water (PWFY) icon
[OFF (BG Color: black)]
[ON (BG Color: blue)]
Schedule (enable/disable)
Air To Water (PWFY) mark

13
[ON (BG Color: blue)]
Schedule (enable/disable)
•Mode
•Check Water sign
Water
temperature
Set
temperature*
Interlocked ventilation (LOSSNAY):
Displays when there are ventilation units interlocked
with the air conditioning (indoor) units in the group.
Icon color indicates the operation status
(Blue: ON, Black: OFF).
General equipment icon:
Displays the general equipment type.
(3) LIST screen
Display selection button
Display selection button
[ON (BG Color: blue)] [OFF (BG Color: black)] [ON (BG Color: blue)]
Group No. Room (Group) name Schedule (enable/disable) Schedule (enable/disable)
Interlocked ventilation (LOSSNAY) operation**
•Check mark
•Mode
•Filter sign:
Room
temperature
Set
temperature* Room
temperature
Interlocked
ventilation**
ON: blue
OFF: black
Room
temperature
•Mode
•Filter sign:
* When the temperature offset function is enabled, the
temperature will appear in the green outline font.
** Interlocked LOSSNAY does not
appear during operation.
[LOSSNAY group]
Group No. Room (Group) name Schedule (enable/disable) Schedule (enable/disable)
[OFF (BG Color: black)]
[ON (BG Color: blue)] [OFF (BG Color: black)] [ON (BG Color: blue)]
[OFF (BG Color: black)]
•Check mark •LOSSNAY icon
•Filter sign: •LOSSNAY icon •LOSSNAY icon
•Filter sign:
[General equipment group]
Group No. Room (Group) name Schedule (enable/disable) Schedule (enable/disable)
[ON (BG Color: blue)] [OFF (BG Color: black)] [ON (BG Color: blue)]
[OFF (BG Color: black)]
•Check mark •General equipment icon •General equipment icon
【Error (BG Color: yellow)】
【Air conditioning unit/LOSSNAY/
General equipment group】
Error display
•General equipment icon
Water temperature:
Display ranges 0-93ºC (32-199ºF). When the
temperature is beyond the range, 0ºC (32ºF) or 93ºC
(199ºF) will blink on the display. When multiple Air To
Water (PWFY) units are registered to a group, current
water temperature on the main Air To Water (PWFY)
unit is displayed.
[Air conditionoing unit group]
[Air To Water (PWFY) group]
Group No. Room (Group) name
•Check mark
Auto (dual set point) mode
[OFF (BG Color: black)] [ON (BG Color: blue)]
[OFF (BG Color: black)]
Cooling set temperature
Schedule (enable/disable)
Heating set
temperature
Water
temperature
• Air To Water
(PWFY) icon
ON: blue
OFF: black
• Air To Water (PWFY) icon
ON: blue, OFF: black
•Mode
•Check Water sign Water
temperature
Air To Water (PWFY) mark

14
Icon Displays [HOME screen]
Auto (dual set point) mode
GROUP screen
[Air conditioning unit group • Air To Water (PWFY) group]
During operation
Group No.
Mode
Error
Startup (communication) error
Filter sign*
Check Water sign**
Energy-saving
Scheduled operation/
Disabled
Disable-Scheduled-
Operation function: ON
Disable-Scheduled-
Operation function: OFF
Interlocked ventilation (LOSSNAY)*
Air direction*
Fan speed* Louver*
Group name
Room temperature*
Water temperature**
Set temperature
Temperature Correction
Interlocked ventilation*
(LOSSNAY)
When the Temperature
Correction function* is enabled
Error: Displays when an error occurs.
Startup (communication) error:
Displays as well as the error display when a startup
(communication) error occurs.
Filter sign: Displays when lter needs maintenance.
During scheduled operation: Displays .
Energy saving: will appear on the screen while
energy-save control is being performed.
(depending on the indoor unit model)
When the Disable-Scheduled-Operation button is
enabled or Timer (Schedule) execution is prohibited
:
Displays .
Room temperature:
Displays the current room temperature. The displayed
temperature will blink when the room temperature is at or
above 40 ºC (104 ºF) (39 ºC (102 ºF) on some models),
or at or below 0 ºC (32 ºF) (8 ºC (46 ºF) on some models).
When multiple air conditioning units (indoor units) are
registered to a group, current indoor temperature on the
main indoor unit is displayed.
Note : While the icon is displayed on the button, the operation is locked.
Unit icon
*: Displayed only on air conditioning unit
groups and when the selected unit
supports the function
**: Displayed only on Air To Water (PWFY)
groups
While the unit is stopped
Cooling set temperature
Heating set temperature

15
[LOSSNAY group]
During operation
Fan speed display
General equipment icon
[General equipment group]
During operation
While the unit is stopped
While the unit is stopped
Water temperature:
Display ranges 0-93ºC (32-199ºF). When
the temperature is beyond the range, 0ºC
(32ºF) or 93ºC (199ºF) will blink on the
display. When multiple Air To Water (PWFY)
units are registered to a group, current water
temperature on the main Air To Water (PWFY)
unit is displayed.
When the Temperature Correction function is
enabled:
When the Temperature Correction function is
enabled, the corrected temperature will appear
in the green outline font.
Interlocked ventilation (LOSSNAY):
Displays the operation status of the ventilation
that is interlocked with the air conditioning
(indoor) units.
General equipment icon:
Displays the general equipment type.

16
Basic Operations
Screen selection
GRID (zoom-out) screen appears at the initial startup.
Select the desired screen.
1
22
1
33
1
2
3
GRID (zoom-out) screen
GRID (zoom-in) screen LIST screen
When the system contains 25 groups or more, the GRID (zoom-out) screen is as shown above.

17
• Group icon setting 1: appears in the area marked 2.
Stops or starts the operation of the air conditioning units through group icon 1.
• Group icon setting 3: Nothing appears in the area marked 2.
Moves to the GROUP screen by touching the group icon 1.
* ON/OFF operation lock
When AT-50B restricts its own ON/OFF operation, the icon above will appear. The ON/OFF
operation will be disabled.
■ When “Emergency Stop (Level signal)” is
displayed
■ When the external input setting is “ON/OFF
(Level signal)”
When the group icon button is set to the Group icon setting 1
Group selection
• Group icon setting 1, 2, 3
When the group icon 1is touched, the action differs depending on the group icon setting.
Three different group icon settings are available as shown below, and default is set to
Group icon setting 2. Refer to P43 for changing the group icon setting.
• Group icon setting 2: appears in the area marked 2.
Allows the user to select groups to be operated. Moves to the
GROUP screen.
Touch the group icon 1to select the group to be operated. Groups can be selected on
the GRID or the LIST screens.
Touch the group icon 1to switch between displaying check marks (selected) and hiding
check marks (deselected). Touch 3to select all groups.
Touch the group icons of the groups to be operated, and then touch 2to move to
the GROUP screen.
The number of selected groups = 1 : The selected group appears on the GROUP screen.
Refer to P18 “GROUP screen” for details.
The number of selected groups > 1 : The Multiple group selection screen appears.
(The selected groups can be operated collectively.)
Refer to P25 “Multiple group selection screen” for details.
* During receiving the external input signal
The ON/OFF button cannot be operated in the following situations.
The button cannot
be operated.

18
Basic Operations
Operation Screen (GROUP screen)
Mode (useable only while the unit is in operation)
Touch 2to access the modes as follows. The selected mode will appear in the area labeled 1.
Air conditioning unit group: Cool/Dry/Fan/Auto*1/Heat
Air To Water (PWFY) group: Heating/Heating ECO/Hot Water/Anti-freeze/Cooling
*1 Depending on the indoor unit model, either one or two set temperatures (single or dual set point(s))
can be set for Auto mode.
ON/OFF operation
Touching 3allows the indoor units in the displayed group to start/stop.
When interlocked ventilation units (LOSSNAY) are connected, the ventilation units work in
conjunction with indoor units. ON: OFF:
*Refer to P53 for Auto mode cooling/heating settings.
*To operate an indoor unit in the heating (cooling) mode
while the indoor unit is already operating in the opposite
mode, the operation mode cannot be changed until all of
the indoor units operate in the same mode or stop. In this
case, the mode 1will blink.
*Available mode varies depending on the model.
Modes that are unavailable do not appear.
*The operation mode which is restricted by this controller or
other controllers cannot be selected.
Basic operations (GROUP screen)
1
2
53
4
Auto heating
display
Auto cooling
display
Operating the air conditioning unit group • Air To Water (PWFY) group
[Green] [Black]
Air To Water (PWFY) group
Air conditioning unit group
Air To Water (PWFY) group
Air conditioning unit group

19
Auto (dual set point) mode:
When the operation mode is set to the Auto (dual set point) mode, two set temperatures
(one each for cooling and heating) can be set. Depending on the room temperature, indoor
unit will automatically operate in either the cooling or heating mode and keep the room
temperature within the preset range.
The set temperatures that are specied for the Cool/Dry mode and the Heat mode will be
used to automatically control the room temperature to stay within the set temperatures.
This mode is especially effective during the in-between seasons, when the temperature
difference between the highest and the lowest is large and both heating and cooling modes
are used within the same day.
Set temp.
(Cool)
Operation pattern during Auto (dual set point) mode
Heat
The room temperature
changes corresponding
to the change in the
outside temperature.
Set temp.
(Heat)
HeatCool Cool
Room
temperature

20
Collective Operation Panel
This panel has the functions that can be
executed collectively. (Setback, Schedule, Mode,
Temperature Correction, RC Prohibition)
Touching the icon at the left bottom of the
icon on the GRID or the LIST screen will bring up
the Collective Operation panel.
Each button has an indicator and the function
name.
The indicators on the buttons show which
functions are assigned to which buttons.
Indicator
Function
Collective
Operation button
▪ Before using the Collective Operation buttons, the groups to execute collective settings on must be selected,
and the parameters must be set from Main Menu>Operation Setting>Collective Operation Setting.
▪ If appears on an icon of a given function, the function is not available.
Performing Collective Operation
1 On the GRID or the LIST screen, touch the button that brings up the Collective Operation panel.
2 Select the Collective Operation button on the Collective Operation panel.
3 Press OK on the Collective Operation panel.
(Go to 4if Setback or Mode was selected. Otherwise, the setting is complete.)
4 If Setback or Mode was selected, take the following steps.
When Setback is selected When Mode is selected
Select the desired item, and touch OK.
▪ Scheduled: Scheduled operation is enabled. The units will
operate according to the Setback Control settings.
(P37)
▪ Unscheduled : Scheduled operation is disabled. The units will
operate according to the Collective Operation
settings (Setback). (P41)
▪ OFF : The Setback function will not be executed.
*Regardless of how the above settings are made, the Setback
function will not be executed while the unit is in operation.
▪ Touch OK on the popup window.
▪ Select a mode on the window that will appear.
▪ Touch OK.
*A blinking indicator on a button indicates that the function that corresponds to the button cannot be
collectively executed. Check the settings for the “Collective Operation Setting.”