Q3 & Qht Controls for Chilled Water Systems Read This Manual Before Proceeding
L-2962 ENGLISH 1
INTRODUCTION
The Q3 and Qht are microcontroller-based units designed for use with chilled water (CW) 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
HOW IT WORKS
The basic principle behind an air conditioner is the movement of heat. In a marine CW air conditioner operating in cool mode,
heat is removed from the inside cabin air and transferred to a closed, fresh water loop that is in turn cooled by the main chiller
system in the engine room or in another equipment space. The chiller system then transfers the heat into the seawater. In heat
mode, the chiller system adds heat to the water loop using either reverse-cycle or electric heating. Then, the CW air conditioner
in the cabin removes the heat from the loop and adds it to the cabin air.
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.
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.
• Water-in sensor for individual cabin heating and cooling.
• 26 programmable functions.
• Nonvolatile memory requires no backup power.
• Humidity Mode control.
• Programmable fan operation.
• Programmable display brightness.
• Air Filter Cleaning or Replacement Timer.
• Outside temperature sensor.
• Chilled water inlet temperature sensor.
• Chilled water outlet temperature sensor.
• Auxiliary heating control capabilities.
• Humidity sensor for advanced humidity control.
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