Trane ACONT900AC43UA, TCONT900AC43UA, Charge Assist Service Manual

Air Conditioning Procedures

Service Guide

Communicating Residential

Comfort Systems

A Comprehensive Reference for Service of Communicating

Residential Air Conditioning, Heat Pump & Gas Furnace Systems

First Edition

© 2010 Trane Inc.
All rights reserved. No part of this book
may be reproduced, in any form or by
any means, without permission in
writing from the publisher.

Produced and printed in the USA

1.0

We appreciate your feedback.....

We value your opinion. If you feel this service guide can be improved in some way, please
give us your thoughts. Simply email your opinion to [e-mail]. You may also
write in the space below , tear out this p age and mail it to:

Trane Company

Attn: Loran Dailey

6200 Troup Hwy.

Tyler , TX 75707

Comments

Air Conditioning Procedures

Name:
Address:
Email:
Phone#

Pub# 034-3457-01

We appreciate your feedback.....

We value your opinion. If you feel this service guide can be improved in some way, please
give us your thoughts. Simply email your opinion to [e-mail]. You may also
write in the space below , tear out this p age and mail it to:

Trane Company

Attn: Loran Dailey

6200 Troup Hwy.

Tyler , TX 75707

Comments

Air Conditioning Procedures

Name:
Address:
Email:
Phone#

Pub# 034-3457-01

WARNING

!

Cautions & Warnings

Throughout this manual there are procedures where voltage may be
present and gas or refrigerant system checks may be required. Read all
cautions and warnings on this page before proceeding.

W ARNING

!

SAFETY HAZARD

THIS INFORMATION IS INTENDED FOR USE BY
INDIVIDUALS POSSESSING ADEQUA TE BACKGROUNDS
OF ELECTRICAL AND MECHANICAL EXPERIENCE. ANY
ATTEMPT T O REPAIR A CENTRAL AIR CONDITIONING
PRODUCT MA Y RESUL T IN PERSONAL INJURY AND OR
PROPERTY DAMAGE. THE MANUFACTURER OR SELLER
CANNOT BE RESPONSIBLE FOR THE INTERPRET ATION
OF THIS INFORMATION, NOR CAN IT ASSUME ANY
LIABILITY IN CONNECTION WITH ITS USE.

W ARNING

!

FIRE OR EXPLOSION HAZARD

FAILURE TO FOLLOW THE SAFETY WARNINGS EXACTLY
COULD RESUL T IN SERIOUS PERSONAL INJURY , PROPERTY
DAMAGE, OR DEATH. IMPROPER SER VICING COULD RESULT
IN DANGEROUS OPERA TION, SERIOUS PERSONAL INJURY ,
PROPERTY DAMAGE, OR DEA TH.

W ARNING

!

SERVICE PROCEDURES HAZARD

BODILY INJURY CAN RESULT FROM HIGH VOLTAGE
ELECTRICAL COMPONENTS, FAST MOVING FANS, AND
COMBUSTIBLE GAS. FOR PROTECTION FROM THESE
INHERENT HAZARDS DURING INSTALLATION AND
SERVICING, THE ELECTRICAL SUPPLY MUST BE
DISCONNECTED AND THE MAIN GAS VALVE MUST BE
TURNED OFF . IF OPERATING CHECKS MUST BE PERFORMED
WITH THE UNIT OPERATING, IT IS THE TECHNICIAN’S
RESPONSIBILITY TO RECOGNIZE THESE HAZARDS AND
PROCEED SAFEL Y .

W ARNING

!

V oltage Hazard

Disconnect power to the unit before removing the
blower door. Allow a minimum of 10 seconds for IFC
power supply to discharge to 0 volts. Failure to follow
this warning could result in property damage, personal

injury or death.

W ARNING

!

CARBON MONOXIDE POISONING HAZARD

FAILURE TO FOLLOW THE SER VICE AND/ OR PERIODIC
MAINTENANCE INSTRUCTIONS FOR THE FURNACE AND
VENTING SYSTEM, COULD RESUL T IN CARBON MONOXIDE
POISONING OR DEATH.

W ARNING

!

FIRE OR EXPLOSION HAZARD

SHOULD OVERHEATING OCCUR, OR THE GAS SUPPL Y FAIL
TO SHUT OFF, SHUT OFF THE GAS VALVE TO THE UNIT
BEFORE SHUTTING OFF THE ELECTRICAL SUPPL Y . FAILURE
TO FOLLOW THIS WARNING COULD RESUL T IN PROPERTY
DAMAGE, PERSONAL INJURY , OR DEA TH.

CAUTION

!

Safety Hazard

Sharp Edge Hazard
Be careful of sharp edges on equipment or any cuts
made on sheet metal while installing or servicing.
Personal injury may result.

Where there is no complete return duct system, the
return connection must be run full size from the furnace
to a location outside the utility room, basement, attic,
or crawl space.

Do NOT install return air through the back of the furnace
cabinet.

Do NOT install return air through the side of the furnace cabinet
on horizontal applications.

NOTE: Minimum return air temperature is 55°F.

CAUTION

!

CONTAINS REFRIGERANT!

SYSTEM CONT AINS OIL AND REFRIGERANT UNDER HIGH
PRESSURE. RECOVER REFRIGERANT TO RELIEVE
PRESSURE BEFORE OPENING SYSTEM.
Failure to follow proper procedures can result in
personal illness or injury or severe equipment damage.

CAUTION

!

LABELING WIRES!

LABEL ALL WIRES PRIOR TO DISCONNECTION WHEN
SERVICING CONTROLS. WIRING ERRORS CAN CAUSE
IMPROPER AND DANGEROUS OPERA TION. VERIFY PROPER
OPERATION AFTER SERVICING .

CAUTION

!

BURN HAZARD

DO NOT TOUCH IGNITER. IT IS EXTREMEL Y HOT .

A 1

Cautions & Warnings

A 2

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(A/T)CONT900AC43UA Installer Guide

Communicating Controller

Section A

Introduction........................................................................................................................................ 3

Product specifications ................................................................................................................... 3

Installation.......................................................................................................................................... 3

When installing this product .......................................................................................................... 3

Location......................................................................................................................................... 4

Selecting Comfort Control location ............................................................................................... 4

Sub-base installation ..................................................................................................................... 4

Wiring............................................................................................................................................ 5

Mounting Comfort Control on sub-base......................................................................................... 6

Initial power-up .................................................................................................................................. 6

Power-up sequence....................................................................................................................... 6

Discovery mode ............................................................................................................................ 6

Communicating indoor unit - Communicating outdoor unit ........................................................... 7

Communicating indoor unit - Single stage cooling unit ................................................................. 7

Adjusting real time clock .................................................................................................................. 7

Setting calendar and time ............................................................................................................. 7

Installer setup (ISU) ........................................................................................................................... 8

Entering installer setup.................................................................................................................. 8

Operation: Using the Comfort Control .......................................................................................... 18

System and fan settings .............................................................................................................. 18

Fan settings................................................................................................................................. 18

LED indication ............................................................................................................................. 18

Filter indication............................................................................................................................ 18

Pre-programmed ......................................................................................................................... 18

Alert code numbers ..................................................................................................................... 18

Equipment damage hazard. Minimum compressor off-time is bypassed during installer

System test ..................................................................................................................................19

System checkout ............................................................................................................................. 19

Installer system test..................................................................................................................... 19

Advanced features........................................................................................................................... 19

Adjustable continuous air flow..................................................................................................... 19

Control response rate .................................................................................................................. 20

Cycle rate .................................................................................................................................... 20

Auto changeover ......................................................................................................................... 20

C - A 1

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Setpoint deadband ...................................................................................................................... 21

Backlit display ............................................................................................................................. 21

Filter reminders ........................................................................................................................... 21

Fan selections ............................................................................................................................. 21

Screen locked.............................................................................................................................. 21

Installer system tests................................................................................................................... 21

Default factory settings................................................................................................................ 21

Wait indicator .............................................................................................................................. 22

Calibrate indoor temperature....................................................................................................... 22

TCONT900AC43UA Installer’s Guide

Calibrate outdoor temperature .................................................................................................... 22

Outdoor temperature sensor ....................................................................................................... 22

Humidification.................................................................................................................................. 22

Indoor humidification control ....................................................................................................... 22

Frost control ................................................................................................................................ 22

Dehumidification ............................................................................................................................. 22

Integrated temperature and humidity control (ITHC)................................................................... 22

Droop ............................................................................................................................................23

Comfort-R™ delay .........................................................................................................................23

Dehumidification airflow .................................................................................................................23

Proprietary humidity control...........................................................................................................23

Special heat pump features ............................................................................................................ 23

Auxiliary heat lockout temperature..............................................................................................23

Compressor heat lockout temperature ........................................................................................ 23

Operation in heat mode............................................................................................................... 24

Defrost heater balance point control ........................................................................................... 24

Operation in emergency heat mode ............................................................................................ 24

Heat pump with fossil fuel heat (dual fuel) and outdoor temperature sensor .............................. 24

Troubleshooting guide ................................................................................................................... 25

C - A 2

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(A/T)CONT900AC43UA Installer Guide

Introduction

The (A/T)CONT900AC43UA is a communicating pro­grammable Comfort Control (See Table 1) that sup­ports single-stage or multi-stage heat/cool and heat
pump applications. It is a wall mounted, low voltage
(24V AC) communicating Comfort Control with backlit
LCD and a touch screen display . Room temperature
is maintained by controlling the operation of heating,
cooling, heat pump, and dual fuel systems via digital,
two-way communications. The Comfort Control will
communicate with and identify all ComfortLink™ II com­ponents in the system. It is easily manually config­ured via the user friendly Installer Setup menu. The
Comfort Control feature includes separate heating and
cooling setpoints, selectable auto or manual
changeover, menu driven 7-day programming, adjust­able filter reminders, and outdoor temperature sens­ing. Setup selections and diagnostics are stored in­definitely in the Comfort Control’s nonvolatile memory ,
eliminating the need for battery backup.

Product specifications

Power source: 18-30 VAC, Class II, 50/60 Hz
Storage range: -30°F to 150°F, 5% to 90% RH non­condensing
Operating temperature range: 0°F to 120°F, 5% to
90% RH non-condensing

System mode: Heat, Cool, Auto, Emergency Heat,
and Off
Fan mode: On, Auto and Circ
Cooling setpoint temperature range: 60°F to 99°F,
1°F resolution
Heating setpoint temperature range: 50°F to 90°F,
1°F resolution
Indoor temperature display range: 40°F to 99°F ,
Outdoor temperature display range: -40°F to 127°F
Indoor humidity display range: 0% to 99%, 1% reso­lution
Minimum cycle off time delay: Compressor, 5 min­utes. Heat, 0 minutes.

The comfort control contains a Lithium battery which
may contain Perchlorate material.
Due to State Law in California, the following st atement
is required:

Perchlorate Material-special handling may apply . See

www.dtsc.ca.gov/hazardouswaste/perchlorate

Installation

When installing this product

Step 1

Read these instructions carefully. Failure to follow
these instructions may damage the product or cause
a hazardous condition.

T able 1

C - A 3

(A/T)CONT900AC43UA Installer Guide

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Step 2

Check the ratings given in the instructions and on
the product to make sure the product is suitable for
your application.

Step 3

Installer must be a trained, experienced service tech­nician.

TCONT900AC43UA Installer’s Guide

Step 4

After completing installation, use these instructions
to check out the product operation.

WARNING

Voltage Hazard. Can cause electrical shock or
equipment damage. Disconnect power before
beginning instructions.

Location

Install the Comfort Control about five feet (1.5m)
above the floor in an area with good circulation at
average temperature (See Figure 1.)

Figure 1

Selecting Comfort Control location

Do not install the Comfort Control where it can be
affected by

• Drafts or dead spots behind doors and in
corners.

• Hot or cold air from ducts.

• Radiant heat from sun or appliances.

• Concealed pipes and chimneys.

• Unheated (uncooled) areas such as an outside
wall behind the Comfort Control.

Sub-base installation

The Comfort Control can be mounted horizontally
on the wall or on a two inch by four inch wiring box.
Position sub-base horizontally on the wall or on a two
inch by four inch wiring box.

Step 1

Turn OFF all power to heating and cooling equip­ment.

Step 2

If an existing Comfort Control is being replaced:

a.)Remove existing Comfort Control from the wall.
b.)Disconnect wires from existing control, one at

a time. Be careful not to allow wires to fall back
into wall.

c.) As each wire is disconnected, record wire color

and terminal marking.

d.)Discard or recycle old Comfort Control.

C - A 4

Step 3

Separate the Comfort Control from the sub-base to
expose mounting holes.

Step 4

Position and level the sub-base wallplate (for appear­ance only.) The Comfort Control functions properly
even when not level.

Communicating Programmable 3-Wire Hookup

4 Heat/3 Cool/ Heat Pump

(A/T)CONT900AC43UA Installer Guide

Step 5

Use a pencil to mark the mounting holes.

Step 6

Remove the sub-base from the wall and drill two 3/
16” holes in the wall (if drywall) as marked.
For firmer material such as plaster, drill two 7/32” holes.
Gently tap anchors (provided) into the drilled holes until
flush with the wall.

Step 7

Position the sub-base over the holes, pulling the wires
through the wiring opening.

Step 8

Insert the mounting screws in the holes and tighten.

Wiring

All wiring must comply with local electrical codes and
ordinances. See Figures 2 and 3 wiring diagrams
for specific equipment applications. Refer to Table
2 for terminal designations.

Figure 2

Figure 3

Field wiring diagram, Communicating indoor unit - Single stage cooling unit

T able 2

Field wiring diagram, Communicating indoor unit - Communicating outdoor unit

WARNING

Voltage Hazard. Can cause electrical shock or
equipment damage. Disconnect power before
beginning instructions.

Note:

The maximum cable length for the entire Comfort Control com­municating system is 500 feet 18 AWG. The maximum dis­tance of any single cable from a transformer is 250 feet 18
AWG.

C - A 5

(A/T)CONT900AC43UA Installer Guide

Step 1

Loosen the terminal screws on the sub-base. Insert
wires into the terminal block next to the loosened
screw (See Figure 4.)

Communicating Programmable 3-Wire Hookup

4 Heat/3 Cool/ Heat Pump

Step 2

Push the Comfort Control straight onto the wallplate
(See Figure 4.)

Step 3

Perform installation of all other system equipment.

Figure 4

TCONT900AC43UA Installer’s Guide

Important: Use 18-gauge color-coded Comfort Control cable for proper
wiring. Shielded cable is not typically required. Keep this wiring at least
one foot away from large inductive loads such as Electronic Air Cleaners,
motors, line starters, lighting ballasts, and large distribution panels. Failure
to follow there wiring practices may introduce electrical interference (noise)
which can cause erratic system operation. All unused Comfort Control wire
to be grounded at indoor unit chassis ground only. Shielded cable may be
required if the above wiring guidelines cannot be met. Ground the shield
only to the system chassis.

Step 2

Securely tighten each terminal screw.

Step 3

Push excess wire back in the hole.

Step 4

Plug the hole in the wall with nonflammable insulation
to help prevent drafts from adversely affecting Comfort
Control operation.

Mounting Comfort Control on sub-base

Step 1

Align the terminal screw block with the pins on the
back of the Comfort Control.

C - A 6

Step 4

Turn ON power to the heating and cooling equip­ment.

Initial power-up

Power-up sequence

The communicating Comfort Control will communicate
and identify all communicating components in the sys­tem.

Discovery mode

Discovery mode begins when the communicating Com­fort Control is first installed and power is connected.
For communicating equipment, the Comfort Control
automatically configures the equipment type, number
of stages, cycle rates for each stage and compressor
stage ratios based on the information it received dur­ing Discovery mode.

While in Discovery mode, the LED indicator located
in the upper right corner of the Comfort Control will
be illuminated.

All discovered values will be saved into memory. If
a communicating device goes missing (Err 89) or
changes in value (Err 126) the error will be broad­cast to the Comfort Control screen (restoring com­munications will clear this error or see ISU 0706 to
reset the system configuration.)

The communicating Comfort Control can be reset
(ISU 0710) to factory default settings.

Note: ISU 0706 Will force a reinitialization without af­fecting presets. ISU 0710 will reset everything includ­ing custom programs and presets.

Communicating Programmable 3-Wire Hookup

4 Heat/3 Cool/ Heat Pump

If no equipment is connected during the Auto-Discov­ery process, the system mode will be stuck at “OFF”
and no equipment will run.

T o change the default/discovery settings, enter the in­staller Setup menu (See Table 4, Pages 9-17) and
select the desired item.

Only ISU settings with an “E” will be Auto-Discovered.
Manually changing an ISU setting to an option other
than “E” disables Discovery mode for that ISU setting.

See Table 3 for default cycle rate settings.

T able 3

(A/T)CONT900AC43UA Installer Guide

Adjusting real time clock

Setting calendar and time

Locate and remove the tab labeled “Remove” in the
lower left corner of the Comfort Control back. The
tab must be removed to activate the real time clock.
(See Figure 5.)

Figure 5

Communicating indoor unit - Communicating
outdoor unit

For a fully communicating system, the communicat­ing Comfort Control will automatically configure the
indoor and outdoor equipment configuration and cycle
rates for each stage (See Figure 2.)

Communicating indoor unit - Single stage
cooling unit

For a partially communicating system, the commu­nicating Comfort Control will automatically config­ure the indoor equipment configuration and cycle
rates for each stage (See Figure 3.)

The outdoor equipment configuration will default to
a single stage cooling unit.

If the system is not powered, the real time clock bat­tery life is approximately 20 weeks.

The Comfort Control is designed to automatically
keep the current time and day in memory for up to
ten years under normal use once calendar is set.
When the Comfort Control is powered, the display is
ready for the calendar date to be entered (See Fig­ure 6, next page)

Note: Clock accuracy is +/- 1 minute per month

C - A 7

(A/T)CONT900AC43UA Installer Guide

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Figure 6

TCONT900AC43UA Installer’s Guide

Installer setup (ISU)

The Comfort Control works with many different sys­tem types. The installer can use the Installer Setup
menu to change factory settings to customize instal­lations (See T able 4.)

Figure 7

Step 4

Release the two blank keys when the screen on the
Comfort Control matches the screen in Figure 8 (See
Figure 8.)

Figure 8

Entering installer setup

Follow these steps to enter the Installer Setup:

Step 1

Be sure the Comfort Control is powered. If neces­sary , press the Done key to return to the home screen.

Step 2

Press and release the system key.

Step 3

Press and hold the two blank keys on either side of
the center key for approximately five seconds until
screen changes (See Figure 7.)

C - A 8

Step 5

See Figure 8 to review how the Comfort Control keys
are used during Installer Setup (See Table 4, Pages
9-17) for the Installer Setup numbers and settings.

Communicating Programmable 3-Wire Hookup

4 Heat/3 Cool/ Heat Pump

Step 6

Press the Done key to exit the Installer Setup.

Note:

Manually changing an ISU setting to an option other than “E”
disables Discovery mode for that ISU setting. If power is lost,
all custom settings are retained in the memory .

T able 4. Inst aller Setup Menu.

(A/T)CONT900AC43UA Installer Guide

C - A 9

(A/T)CONT900AC43UA Installer Guide

Table 4. Installer Setup Menu Continued.

TCONT900AC43UA Installer’s Guide

Communicating Programmable 3-Wire Hookup

No humidity option available if 3 is
selected

4 Heat/3 Cool/ Heat Pump

Note: If single stage is configured, ODU will run Low Stage,
but ID airflow ill be 100%. If 3-Three Stage is configured,
there will be an Err 89 on stat but unit will run.

For 3 stage furnace:
Option 1 = High stage heat only
Option 2 = Medium and high stage heat only

For modulating furnace:
Option 1 = High stage heat
Option 2= Modulating
Option 3 = 40% or 100% - No modulation

Note: If anything else is configured, other than
“E1”, then the blower will not run in cooling with
a furnace but continuous fan and heat will op­erate blower okay/

Note: Auto discovered low stage airflow for 20
SEER:
2 Ton = 50%
3 Ton = 55%
4 Ton = 50%
5 Ton = 65%

C - A 10

Communicating Programmable 3-Wire Hookup

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Table 4. Installer Setup Menu Continued.

(A/T)CONT900AC43UA Installer Guide

Note: E1 = Auto discovered w/com ODU
E0 = Auto discovered w/o com ODU

C - A 11

(A/T)CONT900AC43UA Installer Guide

Table 4. Installer Setup Menu Continued.

TCONT900AC43UA Installer’s Guide

HP with EH = 0 (no lockout)
Dual Fuel = 40 degrees default
(Range is 5 - 60)

Communicating Programmable 3-Wire Hookup

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Note: Y2 counter only with Phase 2 product (serial date
code 0904) if heat demand is satisfied by Y2 - reset timer

Note: “0” is not an option with Dual Fuel (must
have a lockout temp configured)

C - A 12

Dual Fuel = 50 degrees default
Must have option 2 selected in
ISU0350.
(Range is 45-65 with 40 degree de­fault is selected in ISU0350). (A 5 de­gree deadband is enforced between
comp lockout and aux heat lockout)

Note: For phase 2 factory
setting = 0 - disabled.
(phase 2 = serial data code 0904)

Note: Watch for cool air complaints during de­frost if aux heat lockout is configured. Also be
aware of ISU0361, 362 and 363.

Communicating Programmable 3-Wire Hookup

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Table 4. Installer Setup Menu Continued.

Not shown if ODU is 2-stage HP and
3 stages of heat are present

(A/T)CONT900AC43UA Installer Guide

Note 1: RH gives 10-60% range selection on “MORE” screen
Note 2: Dewpoint control gives 0-10 range selection on “MORE”
screen. Either screen shows RH% on “MORE” screen

Option 1 = continuous fan speed (default = 50% cooling CFM
Note: Fan runs for 2 minutes after humidifier demand ends

Phase 2 (serial date code 0904) makes
this option available in USU

ISU0380 must = 1 for this ISU

If “0” is selected, RH% is no
longer displayed on the “MORE”
screen.

Deadband restricted to 5-9 degrees with
ITHC enabled. See ISU0310

C - A 13

(A/T)CONT900AC43UA Installer Guide

Table 4. Installer Setup Menu Continued.

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Only shown if ISU0380 is set to 1 or 4

TCONT900AC43UA Installer’s Guide

C - A 14

Communicating Programmable 3-Wire Hookup

4 Heat/3 Cool/ Heat Pump

Table 4. Installer Setup Menu Continued.

(A/T)CONT900AC43UA Installer Guide

Phase 2 changes range from 50-90

C - A 15

(A/T)CONT900AC43UA Installer Guide

Table 4. Installer Setup Menu Continued.

Phase 1 = 120 seconds
Phase 2 = 0 seconds

Phase 1 = 0 seconds
Phase 2 = 90 seconds

Phase 1 = 0 - disabled
Phase 2 = 5 - 1.5 min@100%

TCONT900AC43UA Installer’s Guide

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C - A 16

Communicating Programmable 3-Wire Hookup

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Table 4. Installer Setup Menu Continued.

(A/T)CONT900AC43UA Installer Guide

C - A 17

(A/T)CONT900AC43UA Installer Guide

Communicating Programmable 3-Wire Hookup

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Operation: Using the Comfort Control

System and fan settings

The system default setting is Heat, unless no Heat
stage is discovered/configured. The fan default is
Auto.

System settings

TCONT900AC43UA Installer’s Guide

Heat: Controls heating system.
Off: Heating and cooling are off.
Cool: Controls cooling system.
Auto: Automatically changes between heating and
cooling systems, depending on indoor temperature
(See Installer Setup section.)
Em. Heat: Compressor is locked out and auxiliary
heat cycles to maintain temperature (used only for
heat pump systems with backup heat.) Maximum
allowable emergency heat stages is three.

Fan settings

Pressing the fan key selects whether the indoor fan
motor runs in the On, Automatic, or Circulation mode.
The fan setting can be programmed into the Com­fort Control schedule for each period (wake, leave,
return, sleep.)

On: Fan runs continuously.
Auto: Fan run is automatically following the fan sched­ule.
Circ: Circulation control will provide a variable circu­lation determined by the Adaptive Intelligent Circu­lation (AIC) algorithm running the fan between 20%
and 60% of the time.

• It indicates that the Comfort Control is in Dis-

covery mode.

Filter indication

The Comfort Control can track up to two filter timers
by total fan run time or calendar days. This feature
can be used to tell the homeowner when to replace
the furnace filter or clean the Air Cleaner cells:

Select filter timer reset time:
Total fan run time: The number of run time days for

the filter timer to count down from: 0, 10, 30, 60, 90,
120, 180, 270, or 365 days (one run time day repre­sents 24 hours or continuous fan/system run time.)

Calendar days: The number of days for the filter timer
to count down from: 0, 30, 60, 90, 120, 180, or 365
days. To activate this feature, select a value other
than 0 (disabled.)

Pre-programmed

Table 5 shows the Energy Star default program set­tings. See owner’s guide for complete instructions
on changing the program (See Table 5.)

T able 5

T able 5. Energy S tar Default Program Settings.

LED indication

An LED indicator is located in the upper right corner
of the Comfort Control. It is only visible when illumi­nated.

• It indicates that there is an Alert.

C - A 18

Alert code numbers

The Comfort Control can receive Alert codes from
any communicating equipment’s buss. The Comfort
Control will illuminate the Red “Service” LED and

Communicating Programmable 3-Wire Hookup

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(A/T)CONT900AC43UA Installer Guide

toggle between the main screen and a screen show­ing the Alert code number . When multiple Alert codes
exist simultaneously, the display will cycle through
each code (showing a maximum of the five most re­cent Alert s) and return to the main screen.

Equipment damage hazard. Minimum
compressor off-time is bypassed during Installer
System T est.

Avoid cycling compressor quickly . Observe compres­sor protection period.

System checkout

Installer system test

The Installer System Test mode is used to test the
Comfort Control operation with HVAC equipment
(See Table 6, Pages 19-20.) System configuration
determines which tests are available and the num­ber of stages shown. While in System Test mode,
the minimum off time is bypassed.

The Installer Test is part of the Installer Setup op­tions. Enter Installer Setup screen and press the
Down arrow key for quick access to the test
selection(s).

• Changing tests will turn equipment off.

• Entering Installer Setup will turn equipment off.

• Charge Assist™ mode not available during
Installer System Tests.

• Test modes times out after five minutes.

Advanced features

Adjustable continuous air flow

The Continuous Fan air flow is user adjustable from
25% to 100% in 5% increments either by entering
the User Setup menu or the Installer Setup menu
(See Table 4, ISU Number 0186, Page 10.)

• Continuous fan mode during cooling operation
may not be appropriate in humid climates. If the
indoor air exceeds 60% relative humidity or sim­ply feels uncomfortably humid, it is

T able 6

T able 6. Inst aller System Tests.

C - A 19

(A/T)CONT900AC43UA Installer Guide

T able 6. Inst aller System T ests Continued.

TCONT900AC43UA Installer’s Guide

Communicating Programmable 3-Wire Hookup

4 Heat/3 Cool/ Heat Pump

recommended that the fan only be used in the
AUTO mode.

Control response rate

A set of more/less aggressive Proportional-Integral
control constants can be chosen to increase/decrease
the responsiveness of the temperature control per­formance. Choosing a more aggressive rate may
cause overshooting. Furthermore, selecting a less
aggressive rate may result in undershooting.

Cycle rate

Cycle rate is the selected number of system cycles
per hour at 50% load. If the cycle rate were set to 3,

C - A 20

each ON/OFF cycle would be 20 minutes long when
operating at 50% load. The total ON and/or OFF
times depends on the actual indoor space load. A
shorter cycle rate may be desired for Heating mode
to maintain tighter control to indoor setpoint. A longer
cycle rate may be desired for Cooling mode to allow
the system to remove moisture from the air and im­prove indoor comfort.

Auto changeover

When the system mode is set to Auto, the control
automatically switches between heating and cooling
modes to maintain the desired comfort level.

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4 Heat/3 Cool/ Heat Pump

(A/T)CONT900AC43UA Installer Guide

Setpoint deadband

The number of degrees separating Heating and Cool­ing setpoints is user adjustable from two to nine de­grees. When the control is set to Auto, and the cool­ing setpoint is changed to a cooler setpoint, the heat­ing setpoint will also change to maintain the selected
deadband. The same action occurs when the Heat­ing setpoint is changed to a warmer temperature.

The deadband is restricted to a range of five to nine
degrees if ISU 0380 is set to Integrated Temperature
and Humidity Control (ITHC.)

Backlit display

When continuous backlight is disabled, the liquid
crystal display will illuminate only when a touchscreen
key is pressed to improve visibility. The backlight
stays on for 45 seconds after the last touchscreen
key press. When continuous backlight is enabled,
the liquid crystal display will remain illuminated con­tinuously. The display will dim to half brightness 45
seconds after the last touchscreen key press.

Filter reminders

The Comfort Control can track up to two filter timers
by total fan run time or calendar days. When the
preset timer(s) has expired to remind the homeowner
that it is time to change the filter(s), “Change” then
“Filter” will automatically flash. To reset either filter
timer, simply press the More key to access the filter
timer value and then press the Reset key . Once the
timer has been reset, the filter timer value can be
viewed at any time by simply pressing the More key
until the filter timer is displayed on the screen.

Both the filter timers are auto discoverable ISU set­tings. If no communicating filtering device has been
discovered, the auto discovered value will default to
zero. T o enable one or both timers, change ISU 0500
and/or ISU 0501 to a value other than zero.

Fan selections

Pressing the Fan key selects whether the indoor fan
motor runs in the On, Automatic, or Circulation mode.
In On mode, the fan motor runs continuously. The
fan automatically follows the fan schedule in Auto­matic mode. Circulation control will provide a vari­able circulation determined by the Adaptive Intelli­gent Circulation (AIC) algorithm running the fan be­tween 20% and 60% of the time. Each scheduled
period (wake, leave, return, sleep) can be pro­grammed with a specific fan setting (on, automatic,
or circulation.)

Screen locked

Locking the control’s touchscreen keys can help pre­vent unwanted tampering with or changing of control
settings. The Comfort Control can either be fully
locked or partially locked. Both options continuously
display “Screen Locked” on the screen. Changing
ISU number 0670 to zero will unlock the keys and
“Screen Locked” will disappear.

Installer system tests

The built-in Installer System Test mode allows the
serviceperson to quickly and easily test the Comfort
Control’s operation with HV AC equipment and makes
diagnostic procedures a snap. System configura­tion determines which tests are available and the
corresponding number of stages shown (See Table
6, Tests 1-6 for details.)

Default factory settings

The Comfort Control is shipped with a set of factory
default settings. The factory default settings can be
restored at any time using the Installer Setup menu
(See Table 4, ISU number 0710, Page 17.)

Before you perform Auto-Discovery mode (ISU num­ber 0710), it is recommended that you record all your
user settings. All user settings choices will be reset

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(A/T)CONT900AC43UA Installer Guide

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4 Heat/3 Cool/ Heat Pump

to factory defaults in Auto-Discovery mode.

Wait indicator

“Wait” will be displayed when the setpoint is changed
in the direction of calling for additional system ca­pacity or the outdoor unit is in Charge Assist™ mode.
“Wait” indicates system time delays are being en­forced, and the control is adjusting to the new set-

TCONT900AC43UA Installer’s Guide

ting.

Calibrate indoor temperature

This option allows calibration of the room tempera­ture sensor. The selected number is number of de­grees, plus or minus, which will be added to the ac­tual temperature. The number can range between
+3 and -3 degrees in one degree increments. Fac­tory default is zero. The adjusted value will be used
as the temperature for both display and control ac­tion.

Calibrate indoor humidity

This option allows calibration of the indoor humidity
sensor. The selected number is percent relative hu­midity , plus or minus, which can be added to the ac­tual indoor humidity . The number can range between
+5 and -5% in one percent increments. Factory de­fault is zero. The adjusted value will be used as the
humidity for both display and control action.

sor becomes unavailable, no outdoor value will be
displayed. The Comfort Control will not send an Alert.

Humidification

Indoor humification control

This feature helps to control the indoor humidity to the
user’s humidification setpoint using a humidifier. The
humidification setpoint can range between 10% and
60% in 5% increments. When enabled, the default
humidification setpoint is 50%.

Frost control

The Frost control requires an outdoor sensor and a
humidifier. The Comfort Control calculates the pos­sibility of condensation or frost forming by using the
outside temperature and inside temperature to de­termine the dewpoint. When the dewpoint could
cause frost or condensation, the humidification re­quest will not be honored.

The Frost control can be accessed by pressing the
More key until the Frost setting is displayed on the
screen. It has a value range of zero to ten, with zero
representing glass with poor insulation and ten rep­resenting glass with perfect insulation. If the factory
setting results in too much condensation or frost on
the windows, lower the setting. When the air seems
too dry, raise the setting.

Outdoor temperature sensor

For accuracy, the initial reading of the outdoor tem­perature sensor requires five minutes to stabilize.
See the Sensor Instructions for installation informa­tion.

If the device is using an outdoor sensor for control
and the outdoor temperature sensor becomes un­available, the display will show dashes “--” and gen­erate an Alert. If the device is not using an outdoor
sensor for control and the outdoor temperature sen-

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Dehumidification

Integrated temperature and humidity control
(ITHC)

The dehumidification control helps to control the in­door humidity to the user’s dehumidification setpoint
by running the compressor. The dehumidification
setpoint can be accessed by pressing the More key
until the dehumidification setpoint is displayed on the
screen. The setpoint can range between 40% and
80% in 5% increments. When enabled, the default