Dometic Qht Operation Manual
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Dometic Qht Operation Manual

Digital controls for direct expansion systems, with bezel
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The Q3 and Qht Digital Controls
For Direct Expansion Systems
O
M
PERATIONS
ANUAL
Q3 Control
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.
 
Qht Control (with bezel)

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  • Page 1 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...

  • Page 2: Table Of Contents

    Table of Contents INTRODUCTION ....... 1 FAULT AND ERROR MESSAGES ....15 .

  • Page 3: Introduction

    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.

  • Page 4: Power Interruptions

    Q3 & Qht Controls for Direct Expansion Systems Operations Manual How It Works 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.

  • Page 5: Description Of The Controls

    Q3 & Qht Controls for Direct Expansion Systems Description of the Controls ESCRIPTION OF THE ONTROLS Figure 1: Q3 Diagram - Control Display Panel and Indicators 13,14 15,16 Table 1: Q3 Diagram Description of Control Display Panel and Indicators Data Display...
  • Page 6 Q3 and Qht Controls for Direct Expansion Systems Description of the Controls Figure 2: Qht Diagram - Control Display Panel and Indicators Table 2: Qht Diagram Description of Control Display Panel and Indicators Data Display - Large LCD readout displays current temperature, Fan Speed Indicator - A row of five bars indicate the current fan set point, programmed values and error messages.

  • Page 7: Important Rogramming Nd Ser

    ISPLAY 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.

  • Page 8: Outside Air Temperature Sensor - Optional

    ODES 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).

  • Page 9: Dehumidification Mode

    Press the MODE and UP buttons simultaneously and repeatedly to select the brightness setting for the display. LEEP 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.

  • Page 10: Anti-Ice Routine

    Program Mode. • Qht - “PROG” flashes in the display while the buttons are being held. When “PROG” stops flashing and a flashing “01” appears in the display, you have successfully entered Program Mode. Press the UP or DOWN buttons to scroll until the desired Programmable Function Number (1-29) is displayed. See Table 4 on page 14.
  • Page 11 Q3 & Qht Controls for Direct Expansion Systems Programmable Functions 2: Fahrenheit, Celsius, or Auto Selection (Factory Default: Fahrenheit) Select F for Fahrenheit. Select C for Celsius. Select Auto to have the system automatically set the unit based on system voltage frequency: For 60 Hz systems, F will be selected as the degree unit;...
  • Page 12 If you select intermittent fan operation, you should relocate the thermistor from the return air grill to a cabin wall where it can best sense the average room temperature. Check with your dealer or call the Dometic Applications Department for more information.
  • Page 13 (Factory Default: On) You can set the Q3’s LED brightness level to dim or you can set the Qht’s backlight to be on or off. Select “SL” for Sleep Mode and the LEDs will remain dim or the backlight will remain off until a key is pressed, which will temporarily brighten the display.
  • Page 14 Medium High Speed = Medium and High LEDs • High Speed = High LED • Qht - Displays 5 bars to indicate the five distinct speed changes or groups the bars to show three distinct speed changes. 23: Aux Heat Enabled/Disabled (Factory Default: “- -” Disabled) The control allows operation of an optional auxiliary (aux) electric heater.
  • Page 15 “Ar” then “FL”. The value entered represents that number times 100 hours. Function values are between 1 (100 hours) and 25 (2500 hours). Dometic recommends that you check the air filter at least every 500 hours of operation.

  • Page 16: Summary Table Of Programmable Functions

    Q3 and Qht Controls for Direct Expansion Systems Programmable Functions UMMARY ABLE OF ROGRAMMABLE UNCTIONS Table 4: Programmable Functions - Ranges and Factory Defaults Function Custom Number Description Factory Default Settings Function Range Compressor Time Delay 0 - 70 seconds...

  • Page 17: Fault And Error Messages

    The display will alternately flash “LO” and “AC”. This is a sustained shutdown, and the system will not resume operation even if the line voltage returns to normal levels. To reset, press the MODE button (Q3) or POWER button (Qht).

  • Page 18: Summary Of Fault Codes Andi

    Enter or exit lock mode by pressing the MODE, UP, and FAN buttons simultaneously. UL flashes for 3 seconds when exiting lock mode. OU or Outside Displays the optional outside temperature as OU (Q3) or Outside (Qht) then the first Continue Operation / 1st digit / 2nd digit followed by second two digits.

  • Page 19: Troubleshooting

    Before you call for service, review this list. It may save you time and expense. This list contains common occurrences that are not a result of defective workmanship or materials. If you need service after trying these procedures, call your nearest Dometic dealer.
  • Page 20 Q3 and Qht Controls for Direct Expansion Systems General System Troubleshooting Table 6: General System Troubleshooting (continued) PROBLEM POSSIBLE REASON/SOLUTION Low airflow. 1. Airflow is blocked. Remove any obstructions in return-air stream. Clean return-air filter and grille. Check for crushed or restricted ducting; ducting must be as straight, smooth and taut as possible.
  • Page 21 Q3 & Qht Controls for Direct Expansion Systems General System Troubleshooting Table 6: General System Troubleshooting (continued) PROBLEM POSSIBLE REASON/SOLUTION Fan coil is iced. 1. Thermostat set point is too low. Raise set point. 2. Improper airflow. Remove any obstructions in return air stream. Clean return air filter and grille.

  • Page 22: Digital-Controls Troubleshooting

    ROUBLESHOOTING See also “General System Troubleshooting” on page 17. Contact an authorized Dometic servicing dealer if the problem continues or for replacement parts. WARNING The control board operates at 115VAC or 230VAC. Make sure the power is off before removing the cover of the control box.

  • Page 23: Maintenance Of System Components

    Q3 & Qht Controls for Direct Expansion Systems Condensate Drains Table 7: Digital-Controls Troubleshooting (continued) PROBLEM POSSIBLE REASON/SOLUTION "Ar / FL" is flashing. Filter needs to be cleaned or replaced. Clean or replace filter. Reset and stop flashing by (Filter Reminder) pressing the FAN, UP, and DOWN buttons simultaneously.

  • Page 24: Seawater Strainer

    Q3 and Qht Controls for Direct Expansion Systems Seawater Strainer EAWATER TRAINER Ensure your pump receives adequate seawater flow by regularly cleaning the strainer basket. Check it daily. Periodically check the overboard discharge for a steady stream of water. Check seawater intake speed scoop for obstructions. Make sure hoses are not looped, kinked or crushed.

  • Page 25: Specifications

    Qht Panel Cut Out ....... . . 3-7/16" (88mm) W x 2-1/8"...

  • Page 26: Sample Wiring Diagrams

    Q3 and Qht Controls for Direct Expansion Systems System Inputs SAMPLE WIRING DIAGRAMS IMPORTANT These are sample diagrams. Wire colors may vary. See unit’s specific diagram located in electrical box. Turn power off before opening electrical box. Figure 3: Sample Digital Control Wiring Diagram (U-Board)
  • Page 27 Q3 & Qht Controls for Direct Expansion Systems System Inputs Figure 4: Sample Digital Control Wiring Diagram (obsolete board) L-2516 ENGLISH...
  • Page 28 DOMETIC MARINE DIVISION 2000 N. Andrews Ave. Pompano Beach, FL 33069 USA +1 954-973-2477 +1 954-979-4414 Email MarineSales@dometic.com 24/7 TECH SUPPORT FOR UNITED STATES AND CANADA 8:00 AM to 5:00 PM Eastern Time: +1 800-542-2477 After hours and weekends: +1 888-440-4494...

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