Quest 746 Dehumidifier: Installation, Operation, and Maintenance Manual

Key Features

• Quiet operation
• Integrated handles
• Patented coil technology
• Industry-leading efficiency
• Superior MERV-13 air filtration
• Environmentally friendly refrigerant
• Auto-restart after power outages

Serial Number: [Field for serial number]

Install Date: [Field for install date]

Sold By: [Field for sold by]

For patents, visit: thermastor.com/patents

Contact: QUESTCLIMATE.COM / (877) 420-1330

Safety Precautions

⚠️ READ AND SAVE THESE INSTRUCTIONS

• The device is designed for indoor installation in a space protected from rain and flooding.
• Install the unit with adequate space for access to back or side panels for maintenance and service. Ensure service panels are accessible.
• Avoid directing discharge air at people or over water in pool areas.
• If used near a pool, spa, or water, ensure the unit cannot fall into the water or be splashed. Use a Ground Fault Interrupt (GFI) protected circuit.
• Do not use the device as a bench or table.
• Do not place the unit directly on structural members. Use vibration isolation to minimize operational vibration and noise.
• A drain pan is required under the unit if installed above a living area or where water leakage could cause damage.
• Never operate the unit with a damaged power cord. Replacement must be done by the manufacturer, its service agent, or a similarly qualified person.
• All electrical connections must comply with the current edition of the NEC ANSI/NFPA 70 and applicable national/local codes.
• Maintain a minimum 1 ft. (0.3m) clearance around air intake and exhaust to prevent obstruction.
• This appliance is not intended for use by persons with reduced physical, sensory, or mental capabilities, or lack of experience/knowledge, unless supervised or instructed by a responsible person. Supervise children to ensure they do not play with the appliance.
• Not intended for use at altitudes over 2000 meters.

1. Intended Application

The Quest 746 Dehumidifier operates in temperatures between 56°F and 95°F. For efficient humidity control, the operating area must be free of water intrusion and excessive fresh air infiltration. Address these issues before installation.

2. Registrations

The Quest 746 Dehumidifier units conform to unified standards: UL 60335-2-40, CSA 22.2 # 60335-2-40:2012 Ed. 1+4. Patents are available at thermastor.com/patents.

3. Specifications @ 80°F/60% RH

* Requires external control not provided.

* Requires buck/boost transformer to run on 208V or 277V.

4. Installation

4.1 Location

The Quest 746 Dehumidifier can be installed in various locations. Adhere to the following cautions:

• Install INDOORS in a space protected from rain and flooding.
• Ensure access to side panels for maintenance and service; do not install with inaccessible service panels.
• Avoid discharging air directly at people or over water in pool areas.
• Ensure the unit cannot fall into water or be splashed.
• Do not use the unit as a bench or table.
• Do not place the unit directly on structural members; use vibration isolation.
• A drain pan is mandatory if installed above a living area or where water leakage could cause damage.
• Do not obstruct air intake and exhaust. Maintain a 4ft clearance around them.
• Permanently removing fixed feet (4038225 and 4038226) invalidates ETL/UL certification. Contact Quest for details.

4.2 Electrical Requirements

High Voltage Connections

Wire the unit directly to the electrical service. Current draw is listed in section 3. Nameplate provides installation and overcurrent protection information. The unit power switch acts as a disconnect. Route power and ground wires through the knockout hole. All wiring must comply with NEC, state, and local codes. A ground fault interrupter protected circuit is recommended.

Low Voltage Connections

Install external controls in a central area to accurately sense humidity. Avoid placing sensors near HVAC registers, exterior doors, or pools/spas. The installer must supply and safely route wiring between the dehumidifier and control panel, avoiding crossing wires. Low voltage (24VAC) controls must NEVER contact high voltage circuits. Control terminals are labeled for clarity. Refer to section 5 for control information.

⚠️ WARNING! Electrical Shock Hazard: Electrical power may be present for some tests. These tests must be performed by qualified service personnel.

4.3 Condensate Water Removal

Condensate drains by gravity via the 3/4" male NPT PVC drain port. An optional condensate pump kit is available if a lift is required. The diagram shows the unit leveled within 2 degrees, with the drain port and an exit pipe running downwards to a drain. The exit pipe should not be submerged in water or sealed to another drain pipe. The trap must be full of water to operate.

Diagram Description: A diagram illustrates the condensate drain port on the unit. An exit pipe connects to this port and must run downwards to a drain. A trap is shown, which must remain full of water. The diagram specifies that water should fall out of the pipe's end and warns against submerging the pipe end or sealing it to another drain pipe.

4.4 Hanging Diagram

The unit can be suspended using four 3/8" threaded rods and four 3/8" jam nuts (not included). The diagram shows the placement of these rods for suspension, indicating dimensions for the unit (e.g., 28.95" width, 27.25" height for suspension points) and a minimum clearance of 6" for the drain outlet. The diagram also shows the intake and treated air flow directions and a minimum 6-inch clearance for the drain outlet.

Diagram Description: This diagram details the hanging points for the Quest 746 Dehumidifier. It shows four suspension points using 3/8" threaded rods and jam nuts. Key dimensions are provided, including the width of the unit (28.95") and the distance between suspension points (27.25"). It also indicates the intake air and treated air flow directions and a minimum 6-inch clearance for the drain outlet.

⚠️ WARNING! Hanging installation must meet all state and local codes.

⚠️ WARNING! Installation should be done by a qualified agency in accordance with these instructions. The qualified service agency is responsible for the installation.

⚠️ WARNING! Check the supporting structure for sufficient load-carrying capacity. Suspend the unit only from the threaded nut retainers, not the cabinet.

❗ CAUTION! Recommended maximum hanger rod length is 6 feet (1.8m).

5. Control Options

The Quest 746 Dehumidifier is controlled by an external remote humidistat via a 24V terminal block. External control is not provided.

5.1 Humidity Control

A 24VAC signal from the remote humidistat activates the fan or both the fan and compressor. Available control options include:

• Quest Cloud Control
• DEH 3000R
• Honeywell Humidistat
• Any 24V signal for dehumidification

❗ CAUTION! Low Voltage Hazard. Can cause equipment damage. Disconnect power before installation.

5.2 24VAC Wiring

The terminal block, low voltage circuit breaker, and power switch are on the intake side. Turn the power switch off before wiring. The FLOAT terminal is for an external normally closed dry contact float switch; no voltage should be applied. Applying voltage may damage the control and void the warranty. If no float switch is used, leave the jumper connected. The DEHU terminal is for dehumidification (compressor and fan operation). R is for 24VAC output. FAN is for fan operation only. C is for 24VAC neutral (common).

Diagram Description (Page 8): Several wiring diagrams illustrate control connections. The "Quest Cloud Control Wiring Diagram" shows connections for 24V IN/COM and 24V OUT. The "Quest DEH 3000R Control Wiring Diagram" shows connections to terminals FLOAT, DHUM, R, FAN, C. The "Honeywell Remote Humidistat Wiring Diagram" depicts similar connections with specific wire colors (Black, Red). The "Daisy Chain" diagram shows how to connect multiple Quest 6 Series units using the DEH 3000R controller, with a note to not wire into the "FAN" terminal for this application.

Note: External devices can be powered between 24V/COM (10VA max). The 24V circuit is protected by a circuit breaker.

6. Maintenance

⚠️ WARNING! Do not operate the unit without a filter or with a less effective filter. Filter non-compliance invalidates the product warranty.

6.1 Standard Air Filter

The Quest 746 comes with two standard MERV 13 efficient pleated fabric filters. Check filters every six months. A dirty filter reduces dehumidifier capacity and efficiency. Access the filter by pulling it straight out; it should be readily visible. For agricultural use, changing the filter with every grow cycle is recommended.

7. Service

⚠️ WARNING! Servicing the Quest 746 involves high-pressure refrigerant systems and high voltage circuitry, posing a hazard that could result in death, serious bodily injury, or property damage. Only qualified service personnel should service this unit.

7.1 Warranty

A warranty certificate is included with the unit. Read it before initiating repairs. For warranty claims or technical assistance, call the factory first at 1-877-420-1330.

7.2 Technical Description (Non Standard Patented)

The Quest 746 Dehumidifier uses a refrigeration system to remove moisture from incoming air and add heat to the discharged air. Hot, high-pressure refrigerant gas flows from the compressor to the condenser coil, where it is cooled and condensed by transferring heat to the outgoing air. The liquid refrigerant then passes through a filter/drier and expansion device, reducing its pressure and temperature. It enters the evaporator coil, where it absorbs heat from the incoming air and evaporates. The compressor then evacuates the cool refrigerant vapor from the evaporator, compresses it to high pressure and temperature, and repeats the cycle.

8. Ducting Guidance

❗ CAUTION! Quest 746 is intended for use in static pressures under 0.5" WG.

• Use custom Therma-Stor Intake and Exhaust Duct Kits for ducting.
• Grills or diffusers on duct ends must not excessively restrict airflow.
• For effective dehumidification, ducting may need to branch to isolated or stagnant flow areas. Use appropriate duct branch sizes to maintain proper airflow.
• System controls should be placed remotely from the dehumidifier in a central location.
• Intake and exhaust ducting should have a minimum of 4 feet from the unit before any turns, with a maximum total run of 25 feet.

❗ CAUTION! Do not connect with a static pressure greater than +0.5" wg. Contact technical support for details.

9. Display

9.1 User Interface

The main status screen displays current information. It includes indicators for Alarm, Prg/Bullseye, and Escape buttons on the left, and Up, Enter, and Down buttons on the right. A sample display shows the date, time, and operational status like 'Call4Dehu', 'Blower: On', 'Compr: On', and 'CC Htr: Off'.

Left side buttons:

• Alarm: Press to check active alarms.
• Prg/Bullseye: Press to access settings and menus.
• Escape: Press to move to the previous menu.

Right side buttons:

• Up: Moves cursor up in menus or increases value on editable fields. Press and hold for faster value changes. Moves to the previous screen if cursor is in the upper left corner.
• Enter: Selects a highlighted menu item or saves an editable value, moving to the next item.
• Down: Moves cursor down in menus or decreases value on editable fields. Press and hold for faster value changes. Moves to the next screen if cursor is in the upper left corner.

9.2 Settings Change Example: Changing Date Display Format

The process involves pressing Prg/Bullseye, entering a password (default 0000), navigating to 'Settings' via Up/Down keys, selecting 'Date/Time', and then selecting the 'Format' field to change it (e.g., from MM/DD/YY to DD/MM/YY). The changes are saved by pressing Enter.

Diagram Description: A series of screenshots illustrate the process of changing the date display format. It shows the password entry screen, the main menu, the settings menu, and the date/time change screen where the format can be adjusted.

9.3 Viewing Active Alarms/Alarm Logs

Pressing the 'Alarm' key displays active alarms, showing the current alarm number, total active alarms, alarm code, description, and timestamp. Pressing Up/Down cycles through alarms. The alarm log screen provides access to the 50 most recent alarms, including when they were triggered and resolved.

Diagram Description: Screenshots show the 'Alarms' screen with details like 'Code', 'Description of Fault', and 'Time/Date Alarm was Triggered'. Another screen indicates how to reset alarms by pressing 'ALARM' for 3 seconds or access the 'DATA LOGGER' via 'ENTER'. The Alarm Log screen is described as similar but shows 'Event: Start' and 'Event: Stop' for triggered and resolved faults.

Note: Resetting an alarm has no effect if the fault condition persists. Active alarms are automatically removed when the fault is resolved.

9.4 Viewing Unit Run Hours

From any screen, press 'Escape' multiple times to return to the main status screen. Press Up/Down until the clock icon appears in the lower-right. Pressing 'Enter' displays the operating hours for the unit, blower, and compressor.

Diagram Description: A screenshot shows the main status screen with a clock icon in the lower right. Another screenshot displays the 'Info' section showing 'Work hours' for the Unit, Blower, and Compressor, with example values like '000048h'.

Wiring Diagram

Diagram Description: The wiring diagram is a detailed schematic illustrating the electrical connections within the Quest 746 Dehumidifier. It shows the input power connections (LINE1, LINE2, LINE3), the 3A breaker, transformer (XFMR), phase monitor, blower contactor, compressor contactor, and various sensors including suction pressure, thermistors (suction, evaporator, inlet), and an electronic expansion valve. It also details connections to the Carel C.Pco Mini High End PLC control board and the display unit, along with terminal designations (FLOAT, DHUM, R, FAN, C) and wire color codes.

Service Parts List

A list of service parts is provided with item numbers, part numbers, and descriptions. Key components include control modules, contactors, transformers, circuit breakers, thermistors, filters, coils, fans, and structural parts like handles and brackets.

Diagram Description: An exploded view diagram of the Quest 746 Dehumidifier is shown, with numbered callouts corresponding to the service parts list, indicating the location of various components on the unit.

Optional Parts List

Optional parts available include a Humidity Controller, DEH 3000R Control (Remote), Cloud Control, Cloud Control Plus, a Pump Kit, Intake Duct Kit, Exhaust Duct Kit, and a Drain Trap Kit.

Warranty

Therma-Stor LLC provides a limited warranty for the Quest 746 Dehumidifier. The first year covers defects in materials and workmanship. The second through fifth years cover the condenser, evaporator, and compressor. The end-user is responsible for labor and transportation charges for parts replacement after the first year. The warranty does not cover damage from misuse, abuse, lack of normal care, or unauthorized repairs. Implied warranties of merchantability and fitness for a particular purpose are limited to the duration of the written warranty. Therma-Stor LLC is not liable for special, indirect, or consequential damages.