Dometic Qht, Q3 Operation Manual
The Q3 and Qht Digital Controls
Q3 Control Qht Control (with bezel)
For Direct Expansion Systems
OPERATIONS MANUAL
Dometic Marine
Rev. 20170710
Part Number 0880107
L-2516 English
COPYRIGHT © 2007-2017 Dometic Corporation. All Rights Reserved.
No part of this publication may be reproduced, translated, stored in a retrieval system, or transmitted in any form or by any means
electronic, mechanical, photocopying, recording or otherwise without prior written consent by Dometic Corporation. Every precaution
has been taken in the preparation of this manual to ensure its accuracy. However, Dometic Corporation assumes no responsibility for
errors and omission. Neither is any liability assumed for damages resulting from the use of this product and information contained
herein.
Table of Contents
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
R
EAD THIS MANUAL BEFORE PROCEEDING . . . . . . . . . 1
CONTROLS OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . 1
F
EATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
H
OW IT WORKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The Importance of Seawater Temperature . . . . 1
Power Interruptions . . . . . . . . . . . . . . . . . . . . . . 2
D
ESCRIPTION OF THE CONTROLS . . . . . . . . . . . . . . . . 3
I
MPORTANT PROGRAMMING NOTES TO INSTALLER AND
END USER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
ORMAL HEATING OR COOLING CYCLE . . . . . . . . . . . . 5
N
R
EVERSING VALVE OPERATION . . . . . . . . . . . . . . . . . 5
INSTALLING THE DISPLAY PANEL . . . . . . . . . . . . . . . 5
M
OUNTING THE DISPLAY . . . . . . . . . . . . . . . . . . . . . . 5
M
OUNTING THE SENSORS . . . . . . . . . . . . . . . . . . . . . . 5
Ambient Temperature Sensor - required . . . . . 5
Seawater Temperature Sensor - optional . . . . . 5
Outside Air Temperature Sensor - optional . . . 6
Humidity Sensor - optional . . . . . . . . . . . . . . . . 6
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
O
PERATOR CONTROLS AND DISPLAY PANEL . . . . . . . . 6
Button Functions . . . . . . . . . . . . . . . . . . . . . . . . 6
M
ODES OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . 6
Power On and Basic Modes . . . . . . . . . . . . . . . 6
Dehumidification Mode . . . . . . . . . . . . . . . . . . . 7
Adjusting the Set Point . . . . . . . . . . . . . . . . . . . 7
Fan Operation and Control . . . . . . . . . . . . . . . . 7
Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Display Inside Cabin Temperature . . . . . . . . . . 7
Dimming the Display . . . . . . . . . . . . . . . . . . . . . 7
Sleep Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Lockout Display Mode . . . . . . . . . . . . . . . . . . . 7
Anti-Ice Routine . . . . . . . . . . . . . . . . . . . . . . . . 8
FAULT AND ERROR MESSAGES . . . . . . . . . . . . . . . . 15
H
IGH-PRESSURE SHUTDOWN (HI / PS) . . . . . . . . . . . 15
In Cool Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 15
In Heat Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 15
L
OW-PRESSURE SHUTDOWN (LO / PS) . . . . . . . . . . . 15
In Cool Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 15
In Heat Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 15
L
OW-VOLTAGE SHUTDOWN (LO / AC) . . . . . . . . . . . . 15
S
UMMARY OF FAULT CODES AND INDICATOR CODES . 16
INITIAL SYSTEM START UP . . . . . . . . . . . . . . . . . . . . 16
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . 17
GENERAL SYSTEM TROUBLESHOOTING . . . . . . . . . . . 17
D
IGITAL-CONTROLS TROUBLESHOOTING . . . . . . . . . . 20
MAINTENANCE OF SYSTEM COMPONENTS . . . . . . 21
ONDENSATE DRAINS . . . . . . . . . . . . . . . . . . . . . . . . 21
C
R
ETURN-AIR FILTER . . . . . . . . . . . . . . . . . . . . . . . . . 21
S
EAWATER CONNECTIONS . . . . . . . . . . . . . . . . . . . . 21
SEAWATER PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
S
EAWATER STRAINER . . . . . . . . . . . . . . . . . . . . . . . . 22
R
EFRIGERANT GAS . . . . . . . . . . . . . . . . . . . . . . . . . . 22
REVERSING VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . 22
C
ONDENSER COIL . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
W
INTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
O
PERATIONAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
D
IMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
CABLE LENGTHS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
S
YSTEM INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SAMPLE WIRING DIAGRAMS . . . . . . . . . . . . . . . . . . . 24
PROGRAMMING THE CONTROL . . . . . . . . . . . . . . . . . 8
P
ROGRAMMING PROCEDURE . . . . . . . . . . . . . . . . . . . . 8
P
ROGRAMMABLE FUNCTIONS . . . . . . . . . . . . . . . . . . . 8
Customizing the Functions . . . . . . . . . . . . . . . . 8
Restoring Factory Default Settings . . . . . . . . . . 8
Description of Functions . . . . . . . . . . . . . . . . . . 8
Summary Table of Programmable Functions . 14
L-2516 ENGLISH
Q3 & Qht Controls for Direct Expansion Systems Read This Manual Before Proceeding
INTRODUCTION
The Q3 and Qht are microcontroller-based units designed for use with reverse-cycle direct expansion (DX) air conditioning
systems. This manual provides all necessary information for proper installation and operation of the Q3 and Qht controls. Poor
installation or misunderstood operating parameters will result in unsatisfactory performance and possible failure.
READ THIS MANUAL BEFORE PROCEEDING
This manual contains essential information concerning the operation of the control system. It is very important that you read and
understand the contents of this manual before using the equipment, and it should be kept on the boat for future reference.
Read this manual completely before you proceed with the installation and operation of the controls. If you have questions or
require assistance with your Q3 or Qht control, call your Dometic dealer or the Service Department at +1 954-973-2477.
The Q3 and Qht controls are covered under the existing Dometic Owner’s Limited Warranty Policy. Incorrect installation, neglect
and system abuse are not covered under the warranty policy.
CONTROLS OVERVIEW
There are two different controls that can operate a Q-Logic or U-Board system:
• Q3 - Rectangular in shape with a bezel look and LED indicators, this display was designed as an economical version of
the Qht. The Q3 control is only compatible with a Q-Logic or U-Board and is not backward compatible with an SMXII
system
• Qht - Using the newest high-technology (ht), this European-style control with LCD display fits into a decorative Vimar®
Idea bezel and has many new features. The Qht control is only compatible with a Q-Logic or U-Board and it is not
backward compatible with an SMXII system. To distinguish between Qht and SMXht, the Qht has a "Compatible With
Q-Logic Only" label displayed on the Qht mounting flange.
While the programming procedure of the Q3 and Qht controls is the same, there are differences in the look of the buttons and
and the way the information is presented in the displays. Differences are noted in this manual where applicable. Familiarize
yourself with the operation and programming sections of this manual.
FEATURES
Standard Features Optional Features
• Universal 115/230 volt, 50/60 Hz AC power supply.
• User-friendly four- and five-button display panels.
• Option to display temperature in degrees Fahrenheit or
Celsius.
• 33 programmable functions.
• Nonvolatile memory requires no backup power.
• Switch inputs for High/Low Refrigerant pressure.
• Humidity Mode control.
• Anti-icing cycle prevents evaporator icing.
• Programmable fan operation.
• Programmable compressor delays.
• Programmable display brightness.
• Air Filter Cleaning or Replacement Timer.
• Low-Voltage Monitor.
HOW IT WORKS
The basic principle behind an air conditioner is the movement of heat. In a marine DX air conditioner, heat is removed from the
inside cabin air and transferred to the seawater. In reverse-cycle heating, the refrigerant flow is reversed and heat is extracted
from the seawater and discharged into the living space. The efficiency of the system operation depends on both seawater and
cabin temperatures.
• Outside temperature sensor.
• Seawater inlet temperature sensor.
• Auxiliary heating control capabilities.
• Humidity sensor for advanced humidity control.
THE IMPORTANCE OF SEAWATER TEMPERATURE
In Cool Mode, the air conditioner will operate most efficiently in seawater temperatures below 90°F (32°C). At higher seawater
temperatures the unit will operate, but at a reduced capacity. A high-pressure shutdown may occur at higher seawater
temperatures.
L-2516 ENGLISH 1
How It Works Q3 & Qht Controls for Direct Expansion Systems Operations Manual
In Heat Mode, the opposite is true. As the seawater gets colder, there is less heat available, and the heating efficiency is
reduced. Full heating capacity is obtained at approximately 55°F (13°C) seawater temperature. Performance drops to about
50% of rated capacity in 40°F (4.4°C) water. Below this, the system pressure can be so low that the unit will shut down on lowpressure fault. This problem is compounded when the cabin is also cold. See “FAULT AND ERROR MESSAGES” on page 15.
WARNING
Do not operate your air conditioning unit in water that is colder than 38°F (3.3°C). Doing so could lead to water freezing
in the condenser coil which can cause damage to the unit.
POWER INTERRUPTIONS
The control board has built-in protection against sudden power interruptions. The system automatically stores the current
operating configuration in permanent memory every time any changes are made. When AC power is lost, the control board
retains these settings and resumes using them when AC power is restored.
2 L-2516 ENGLISH
Q3 & Qht Controls for Direct Expansion Systems Description of the Controls
4
1
2
3
765
8
9
11
12
13,14 15,16
10
DESCRIPTION OF THE CONTROLS
Figure 1: Q3 Diagram - Control Display Panel and Indicators
Table 1: Q3 Diagram Description of Control Display Panel and Indicators
1
Data Display - Large LED readout displays current
temperature, set point, programmed values and error messages.
9
AUTO Mode Indicator - Lights when Auto Mode is selected.
Flashes if optional Aux Heater is enabled (see Programmable
Function “23: Aux Heat Enabled/Disabled” on page 12).
2
AUTO Fan Mode Indicator - Lights when fan is running in
Automatic Fan Mode.
3
Fan Speed Indicators - Column of three LEDs that indicate
the current fan speed of high, medium, or low (refer to fan speed
operation).
4
FAN Button - Press to select Automatic or Manual Fan Mode,
indicated by the AUTO Fan LED indicator being on or off. In
Manual Fan Mode, additional presses of the Fan button will
adjust fan speed higher, then lower, then back to AUTO. In
AUTO Fan, fan speed is controlled by the control board as a
function of the difference between set point and inside
temperature. See Programmable Function “4: Fan Response
Differential” on page 9.
5
UP Button - Press to adjust set point up. In programming mode
press to scroll through program modes and adjust values.
6
DOWN Button - Press to adjust set point down. In
programming mode press to scroll through program modes and
adjust values.
7
MODE Button - Press to cycle through the modes of operation
(refer to indicators). Mode sequence selections are OFF, COOL,
HEAT, AUX HEAT (optional), AUTO, and DEHUMIDIFY.
10
HEAT/AUX HEAT Mode Indicator - Lights when Heat Mode
is selected or indicates compressor is on when heating in
AUTO mode. Flashes when you press the MODE button a
second time in Heat Mode to select the optional Aux Heat
Mode (refer to Aux Heat Operation).
11
COOL Mode Indicator - Lights when Cool Mode is selected
or indicates compressor is on when cooling in AUTO mode.
12
OFF Mode Indicator - Lights when system is off. Note that
the Data Display remains on. You can continue to adjust set
point, display temperature readings and activate the manual
fan to circulate air while the system is in the Off Mode.
13
Cooling Indicator - A dot in the upper left corner of the data
display lights to indicate the compressor is running in COOL
mode. In AUTO mode, the COOL LED indicator lights to
indicate the compressor is running.
14
Heating Indicator - A dot in the upper left corner of the data
display lights to indicate the compressor is running in HEAT
mode. In AUTO mode, the HEAT LED indicator lights to
indicate the compressor is running.
15
Set Point Indicator - A dot in the upper center of the display
lights to indicate the set point is being adjusted. Normally
display defaults to inside temperature.
8
DEHUMIDIFY Mode Indicator - Lights when the Dehumidify
Mode is selected. Flashes if optional humidity sensor is
connected and operating in Cooling Mode.
16
Manual Fan Mode Indicator - AUTO Fan indicator turns off
when fan is running in Manual Fan Mode.
L-2516 ENGLISH 3
Description of the Controls Q3 and Qht Controls for Direct Expansion Systems
1
28769
10
12131416
11
15
435
Figure 2: Qht Diagram - Control Display Panel and Indicators
Table 2: Qht Diagram Description of Control Display Panel and Indicators
1 Data Display - Large LCD readout displays current temperature,
set point, programmed values and error messages.
9 Fan Speed Indicator - A row of five bars indicate the current fan
speed, with more bars indicating a higher fan speed and fewer bars
indicating a lower fan speed.
2 Set Point Indicator - Display shows SET when set point is being
adjusted. Normally display defaults to inside temperature.
3 Aux Heating Indicator and Aux Heat Mode Indicator (optional) -
A solid dot displays next to the words AUX HEAT when the electric
heater is on and running in Aux Heat mode. The words AUX HEAT
display when you are in Aux Heat mode. (Press the MODE button
to select the optional Aux Heat Mode.) See Programmable Function
“23: Aux Heat Enabled/Disabled” on page 12.
4 Heating Indicator - A solid dot displays next to the word HEAT
when the compressor is on and running in Heat mode.
5 Cooling Indicator - A solid dot displays next to the word COOL
when the compressor is on and running in Cool mode.
6 Cool Mode Indicator - The word COOL displays when you are in
Cool mode. (Press the MODE button to select Cool Mode.)
7 Heat Mode Indicator - The word HEAT displays when you are in
Heat mode. (Press the MODE button to select Heat Mode.)
8 AUTO Mode Indicator - A bracket and the word AUTO display to
the right of the words COOL and HEAT when you are in Auto Mode.
If optional Aux Heat is enabled (see Programmable Function “23:
Aux Heat Enabled/Disabled” on page 12), a bracket and the word
AUTO display to the right of the words COOL and AUX HEAT.
(Press the MODE button to select Auto Mode.)
10 Fan Mode Indicator - The word MANUAL displays when the fan is
running in Manual Fan Mode. The word MANUAL does not display
when the fan is running in Automatic Fan Mode.
11 Dehumidify Mode Indicator - The word DEHUMIDIFY displays
when you are in Dehumidification Mode. It flashes if optional
humidity sensor is connected and operating in the Cooling Mode.
(Press the MODE button to select Dehumidification Mode.)
12 FAN Button - Press to select Manual or Automatic Fan Mode,
indicated by the word MANUAL displaying or not displaying. In
Manual Fan Mode, additional presses of the FAN button will adjust
fan speed higher, then lower, then back to Automatic. In Automatic
Fan Mode, fan speed is controlled by the control board as a
function of the difference between set point and inside
temperature. See Programmable Function “4: Fan Response
Differential” on page 9.
13 UP Button - Press to adjust set point up. In programming mode
press to scroll through program modes and adjust values.
14 DOWN Button - Press to adjust set point down. In programming
mode press to scroll through program modes and adjust values.
15 MODE Button - Press to cycle through the modes of operation
(refer to indicators). Mode sequence selections are COOL, HEAT,
AUTO, AUX HEAT (optional), and DEHUMIDIFY.
16 POWER Button - Press to turn the system on and off. Note that
the Data Display remains on in the Off mode. You can continue to
adjust set point, display temperature readings and activate the
manual fan to circulate air while the system is in the Off Mode.
4 L-2516 ENGLISH
Q3 & Qht Controls for Direct Expansion Systems Important Programming Notes To Installer and End User
IMPORTANT PROGRAMMING NOTES TO INSTALLER AND END USER
If your air conditioning unit is Cool Only (does not have a reversing valve), then you MUST set Programmable Function 19 to
“CL” for Cool Only. Once this parameter is set, the only allowable operational modes that can be selected are OFF, COOL, and
DEHUMIDIFICATION. (See Programmable Function “19: Cool-Only Mode” on page 12 for more information.)
NORMAL HEATING OR COOLING CYCLE
In Automatic Mode, heating and cooling are supplied as required. If Cooling is required, the system will start a cooling cycle
when the cabin temperature exceeds the set point by the Compressor Differential setting in Programmable Function 3 (1.5°F/
0.8°C by default) and will continue to cool until the temperature equals the set point. Similarly, if Heating is required, the system
will start a heating cycle when the cabin temperature is below the set point by the Compressor Differential setting and will
continue to heat until the temperature equals the set point.
If you select Cool Mode, only cooling is supplied. If you select Heat or (optional) Aux Heat Mode, only heating is supplied. The
cabin temperature in either mode is maintained within the Compressor Differential setting.
During a Cooling or Heating cycle, the fan will operate at a fan speed depending on the fan’s operational mode. If a Manual fan
speed is selected, the fan will operate at this speed at all times, even if the set point has been satisfied and the cooling or
heating cycle has ended. If the fan is in Auto mode, the fan speed will be determined by Programmable Function 4, the Fan
Response Differential, and Programmable Function 22, Fan-Speed Divisions. Please refer to these parameters for further
details on the fan speeds during Auto fan operation. When in Auto fan mode, the fan speed will return to low speed once the set
point temperature has been satisfied and the cooling or heating cycle has ended.
REVERSING VALVE OPERATION
The position of the reversing valve determines if the system is in Cool Mode or Heat Mode. When the reversing valve is not
energized, the system will operate in Cool Mode. When energized, the system will operate in reverse-cycle heating. In addition,
the reversing valve will toggle (switch back and forth) to relieve the system’s internal refrigerant pressures in these situations:
• Just before the system starts the compressor if the compressor has not run for less than 2 minutes.
• When a cycle is interrupted from the display panel by pressing the POWER button or changing the set point.
INSTALLING THE DISPLAY PANEL
MOUNTING THE DISPLAY
1. For the Qht display, make a rectangular cut-out in the panel where it will be mounted. The Qht cut-out size is 3-7/16”
(88mm) wide by 2-1/8” (54mm) high. For the Q3 display, only a 1” (26mm) round hole is required in the panel for
mounting.
2. Use the installation instructions included with your display to complete the mounting, securing the display with the
appropriate size and number of screws.
3. Plug one end of the display cable (6-pin connector) to the back of the display and the other end to socket labeled
“Display” located on the edge of the circuit board.
MOUNTING THE SENSORS
NOTE
Do not staple any sensor cables when mounting.
AMBIENT TEMPERATURE SENSOR - REQUIRED
Install the ambient temperature sensor in a proper location to accurately sense the room air temperature. Ideally, the sensor
should be located in a reliable return-air stream moving from the room to be controlled to the air conditioner it is plugged into.
Locating the sensor on the back of the air conditioner coil is not ideal and can result in false readings for several reasons. It is
best to locate the sensor just inside of a return-air grille or passage. The standard cable length for the remote air sensor is 7 feet
(2.1m). Plug in the sensor’s 6-pin connector to the “Inside Temp” socket located on the edge of the circuit board.
SEAWATER TEMPERATURE SENSOR - OPTIONAL
Install the optional seawater temperature sensor to monitor the temperature of the seawater feeding the air conditioner. Ensure
that the sensor is in direct contact with the copper pipe and use thermal mastic to ensure good heat transfer. Strap the sensor
wire in place for strain relief and to prevent the sensor from being accidentally removed. Plug the sensor’s 2-pin connector into
the “Loop Water Out” (blue) socket located in the corner of the circuit board.
L-2516 ENGLISH 5
Operator Controls and Display Panel Q3 and Qht Controls for Direct Expansion Systems
OUTSIDE AIR TEMPERATURE SENSOR - OPTIONAL
Install the optional outside air temperature sensor to monitor temperature outside the cabin. Outside air sensor cables are
available in various lengths. Mount the sensor outside but not in direct sunlight. Plug in the sensor’s 6-pin connector to the
socket labeled “Outside Temp” (white) located on the edge of the circuit board.
HUMIDITY SENSOR - OPTIONAL
Install the optional humidity/temperature combo sensor to monitor the relative humidity of the cabin. Locate the sensor in the
same location as the ambient air temperature sensor. Plug in the combo sensor’s 6-pin connector to the “Inside Temp” socket
located on the edge of the circuit board. The control board automatically detects the presence of this combo sensor and
immediately starts measuring humidity.
OPERATION
OPERATOR CONTROLS AND DISPLAY PANEL
For the button locations and display functions, refer to Figure 1, Table 1 on page 3 for the Q3 control and to Figure 2, Table 2 on
page 4 for the Qht control.
BUTTON FUNCTIONS
• POWER button (Qht only) - Press and release to toggle between the On and Off Modes.
• MODE button - Press and release to toggle between the Off (Q3 only) and all other modes of operation.
• UP button - Press and release to display the set point. Press and hold the UP button to increase the set point. Set
point increases one degree each time the button is pressed.
• DOWN button - Press and release to display the set point. Press and hold the DOWN button to decrease the set
point. Set point decreases one degree each time the button is pressed.
• FAN button - Press to select the Automatic Fan Mode, the Manual Fan Mode, or to advance through the manual fan
speeds.
• Display Seawater Temperature (optional) - Press the FAN and UP buttons simultaneously to display the seawater
temperature (optional). If the seawater temperature is not available, open or shorted (closed), the display flashes “- -”
instead of a temperature reading.
• Q3 - The display flashes “SE” for one second then the seawater temperature displays in two segments: The
display flashes the first digit of the seawater temperature for one second, then the next two digits of the seawater
temperature for one second. The cycle repeats until the buttons are released.
• Qht - The word WATER displays, “SE” flashes for one second, then the seawater temperature displays in two
segments: The display flashes the first digit of the seawater temperature for one second, then the next two digits
of the seawater temperature for one second. The cycle repeats until the buttons are released.
• Display Outside Temperature (optional) - Press the FAN and DOWN buttons simultaneously to display the outside
temperature (optional). If outside temperature is not available, open or shorted (closed), the display flashes “- -”
instead of a temperature reading.
• Q3 - The display flashes “OU” for one second then the outside temperature displays in two segments: The display
flashes the first digit of outside temperature for one second, then the next two digits of outside temperature for one
second. The cycle repeats until the buttons are released.
• Qht - The word OUTSIDE displays, “OU” flashes for one second, then the outside temperature displays in two
segments: The display flashes the first digit of outside temperature for one second, then the next two digits of
outside temperature for one second. The cycle repeats until the buttons are released.
• Display Relative Humidity (optional) - Press the MODE and UP and DOWN buttons simultaneously to display the
relative humidity (optional). “HS” displays for one second then the two digits of relative humidity display for one second.
The cycle repeats until the buttons are released. If HS is not available, open or shorted (closed), the display flashes
“- -” instead of the humidity reading.
MODES OF OPERATION
POWER ON AND BASIC MODES
Press the MODE (Q3) or POWER (Qht) button to turn the system on. In three seconds, the system will start operating in
whichever mode it was running prior to the last shut down. For the initial startup, the control will be in Cool Mode.To change
mode before the system starts, press the MODE button before the three-second startup completes (while the display is
flashing). Or, while the system is on, press the MODE button at any time to change the mode.
6 L-2516 ENGLISH
Q3 & Qht Controls for Direct Expansion Systems Modes of Operation
The modes available are: Off, Cool, Heat, Auto (automatically switches between Cool and Heat Modes, depending on set point
requirement), Aux Heat (optional) and Dehumidification Mode.
DEHUMIDIFICATION MODE
Press the MODE button until the DEHUMIDIFY LED indicator lights (Q3) or the word DEHUMIDIFY appears in the display
(Qht). The display flashes “HU” during this mode of operation. When Dehumidification Mode is activated, the Humidity Control
Program automatically turns the air conditioning system on at timed intervals to remove moisture from the air. The system is
programmed at the factory for average values. To change the factory settings, see Programmable Function “10:
Dehumidification Pre-Circulation Time” on page 10, Programmable Function “11: Dehumidification Time” on page 10, and
Programmable Function “12: Dehumidification Overall Time Period” on page 10.
NOTE
When the system is in Dehumidification Mode, all system safeguard controls remain active. For example, if the line
voltage falls below preset limits, the system will automatically shut down. Or, if AC power is interrupted, the system
will automatically resume operation in Dehumidification Mode when power is restored.
ADJUSTING THE SET POINT
To view the set point, momentarily press and release the UP or DOWN button. To adjust the set point, press the UP or DOWN
buttons to set the desired room temperature (press and hold either button to scroll). The set point range is 55-99°F (12.8-
37.2°C). After selecting the desired set point temperature, if no buttons are pressed for three seconds the display automatically
reverts to showing the inside cabin temperature. Inside cabin temperature is continuously displayed.
• Q3 - The upper center dot in the display lights when set point is being adjusted.
• Qht - The word SET appears in the display while set point is being adjusted.
FAN OPERATION AND CONTROL
Press the FAN button to adjust the fan speed while in Manual Fan Speed Mode or to switch between Manual and Automatic Fan
Speed Modes. The fan may be run manually whether the system is on or off. Automatic Fan Speed Mode can only operate
when the system is on. Fan behavior also depends on how the Fan Mode function is programmed: “C” for continuous or “I” for
intermittent running with the compressor. See Programmable Function “7: Fan Mode” on page 9.
• Q3 - When in Manual Fan mode, the AUTO Fan LED is off.
• Qht - The word MANUAL appears in the display when in Manual Fan mode.
MEMORY
The control has nonvolatile memory requiring no batteries or backup power. When power is lost, the operating parameters are
retained indefinitely. When power is restored, the control resumes operating as last programmed.
DISPLAY INSIDE CABIN TEMPERATURE
The control continuously displays inside cabin temperature. If Mode or Set Point is changed, after three seconds the display
automatically reverts to showing inside temperature. If inside temperature is greater than 99°F (37°C) or less then 0°F (-17°C),
the display shows either 99°F (37°C) or 0°F (-17°C) respectively as the maximum or minimum inside temperature.
DIMMING THE DISPLAY
Press the MODE and UP buttons simultaneously and repeatedly to select the brightness setting for the display.
SLEEP MODE
Sleep Mode dims all LEDs (Q3) or turns off the backlight (Qht). When in Sleep Mode, press any button to brighten the display,
and then operate as usual. See Programmable Function “18: Sleep Mode” on page 11.
LOCKOUT DISPLAY MODE
Press the MODE and UP and FAN buttons simultaneously to select the Lockout Display Mode setting. This mode locks the
display in the current mode selected. If a button is pressed, the display flashes “LC” for 2 seconds then goes back to displaying
the inside temperature. In Lockout Mode, the display shows inside temperature and the indicators operate as normal, but all
button presses are ignored until MODE and UP and FAN buttons are pressed simultaneously, then “UL” displays momentarily
and the buttons are unlocked for normal operation. In Lockout Mode all sensors operate as normal and any fault and error
codes will be displayed.
L-2516 ENGLISH 7
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