ACCUREX 474891 Packaged DX Module Installation Guide

ACCUREX 474891 Packaged DX Module

Specifications

• Product Name: Packaged DX Module
• Usage: Make-Up Air
• Installation: Outdoor
• Function: Cooling only

Product Overview

• The Packaged DX Module for makeup air is a horizontally configured unit designed for outdoor installations. It is used to temper the air supplied to the building, providing cooling to replace the exhausted air.

Installation Instructions

• This module is part of a makeup air unit and should be handled according to the unit’s Installation, Operation, and Maintenance (IOM) Manual. Follow instructions for receiving, unpacking, and handling.

Unpacking

• The unit is shipped as a completely installed unit with protective coverings on the condenser coil. Leave coverings until installation is complete. Verify receipt of the P Trap kit and refer to the IOM for unpacking instructions.

Handling

• Rig and move units using the provided lifting brackets. Do not use forklifts. Refer to the Handling section in the unit’s IOM for detailed instructions.

Storage

• If immediate installation is not possible, take precautions to prevent unit deterioration during storage. The user assumes responsibility for storage. The manufacturer is not liable for storage damage.
• Follow the recommended storage guidelines provided in the manual.

FAQ

Q: What should I do if there is a refrigerant leak?

A: In case of a refrigerant leak, immediately evacuate and ventilate the area. Engage an EPA Certified Technician for repairs. Refrigerant leaks can be harmful.

Q: Can I open access doors while the unit is running?

A: No, never open access doors while the unit is running to prevent accidents or injuries.

• Please read and save these instructions for future reference. Read carefully before attempting to assemble, install, operate, or maintain the product described.
• Protect yourself and others by observing all safety information. Failure to comply with these instructions will result in voiding of the product warranty and may result in personal injury and/or property damage.

General Safety Information

• Only qualified personnel should install and maintain this system. Personnel should have a clear understanding of these instructions and should be aware of general safety precautions.
• Improper installation can result in electric shock, possible injury due to coming in contact with moving parts, as well as other potential hazards.
• Other considerations may be required if high winds or seismic activity are present. If more information is needed, contact a licensed professional engineer before moving forward.

1. Follow all local electrical and safety codes, as well as the National Electrical Code (NEC), and the National Fire Protection Agency (NFPA), where applicable. Follow the Canadian Electrical Code (CEC) in Canada.
2. The unit must be securely and adequately grounded.
3. Verify that the power source is compatible with the equipment.
4. Never open access doors to the unit while it is running.

DANGER

• Always disconnect power before working on or near this equipment. Lock and tag the disconnect switch or breaker to prevent accidental power-up.
• If this unit is equipped with optional gas accessories, turn off the gas supply whenever the power is disconnected.

CAUTION

• This unit is equipped with a compressed refrigerant system. If a leak in the system should occur, immediately evacuate and ventilate the area.
• An EPA Certified Technician must be engaged to make repairs or corrections. Refrigerant leaks may also cause bodily harm.

CAUTION

• When servicing the unit, the internal components may be hot enough to cause pain or injury. Allow time for cooling before servicing.

Receiving

• This module is installed as a component of a make‑up air unit and does not require any special handling.
• Refer to the Receiving portion of the unit Installation, Operation, and Maintenance (IOM) Manual for complete instructions on receiving, unpacking and handling.

Unpacking

• The unit is shipped as a completely installed unit. Protective coverings have been installed on the face of the condenser coil that should be left in place until installation of the unit is complete.
• The only item shipped loose with the unit is the P Trap kit. Verify that the P Trap kit has been received. Refer to Unpacking instructions in unit IOM.

Handling

• Units are to be rigged and moved by the lifting brackets provided. Do not forklift. Refer to the Handling portion of the unit IOM for complete instructions on handling.

Storage

• Units are protected against damage during shipment. If the unit cannot be installed and operated immediately, precautions need to be taken to prevent deterioration of the unit during storage.
• The user assumes responsibility for the unit and accessories during storage. The manufacturer will not be responsible for damage during storage. The following suggestions are provided solely as a convenience to the user.

Inspection and Maintenance During Storage

• While in storage, inspect units once per month. Keep a record of inspection and maintenance performed. If moisture or dirt accumulations are found on the parts, the source should be located and eliminated.
• At each inspection, rotate all moving parts by hand ten to fifteen revolutions to distribute lubricant on the motor and bearings. If paint deterioration begins, consideration should be given to touch‑up or repainting.
• Units with special coatings may require special techniques for touch‑up or repair.
• Machined parts coated with rust preventative should be restored to good condition promptly if signs of rust occur. Immediately remove the original rust-preventative coating with petroleum solvent and clean it with lint‑free cloths.
• Polish any remaining rust from the surface with crocus cloth or fine emery paper and oil. Do not destroy the continuity of the surfaces. Wipe clean thoroughly with Tectyl® 506 (Ashland, Inc.) or the equivalent.
• For hard-to-reach internal surfaces or occasional use, consider using Tectyl® 511M Rust Preventative or WD‑40® or the equivalent.

Product Overview

• The Packaged DX Module for make‑up air is a horizontally configured unit that is installed as a complete package that has been designed for outdoor installations. The Packaged DX Module is used to temper the air that is supplied to the building.
• The make‑up air unit is designed to provide supply air to replace the air that is exhausted from the building. The PDX module is designed to provide only cooling.
• The DX system comes fully charged with R‑410A refrigerant from the factory and is ready for operation upon arrival.
• Units may be supplied with one or two compressors based on the required cooling capacity. All units with multiple compressors allow for staging of compressors to meet a wider range of outdoor air loads while reducing the number of cycles per compressor.
• Optionally, one or one of two supplied compressors may be a digital scroll-type compressor.

Compressed Refrigerant

• All packaged DX modules are charged with environmentally friendly R‑410A compressed refrigerant. Do not use tools or parts designed for other refrigerants on this unit.

Safety Listing

• Make‑up air units are listed per ANSI/UL 1995, Heating and Cooling Equipment, and are ETL Certified.
• Supplemental Installation, Operation and Maintenance Manuals
• Refer to the Installation, Operation, and Maintenance manual for the Make‑Up Air unit for additional information.

Models and Capacities

• The Packaged DX Module for make‑up air units is manufactured in three different platform sizes, each of which has several different output tonnage options.
• Examine shipping documents to verify the correct model of the module as received.

Model Number

A metal plate is located on the fixed panel access to the control center. The plate is marked with the Platform type and Tonnage.

Subassemblies

Coils

• Every module is supplied with a single DX evaporator coil. If there is only one cooling circuit, then the DX coil is not divided.
• If two cooling circuits are specified, then the DX coil will be a split face.
• A single condenser coil is attached to the exterior of the module. If more than one cooling circuit is present, that condenser coil will be of split‑face configuration.

DX System

• The DX system in the module is a complete, sealed unit with compressed R‑410A refrigerant.
• It consists of one or two compressors, evaporator, and condenser coils, and the following integral components:
• expansion valves
• liquid line filter‑drier
• service/charging valves
• moisture indicating sight glass
• crankcase heater on each compressor
• hot gas bypass valve (optional, single circuit units only)

Each DX system incorporates the following:

• high-pressure manual reset cutout
• low-pressure auto‑reset cutout

Installation

Service Clearances

• All make‑up air units require minimum clearances on all sides for routine maintenance. Filter replacement, drain pan inspection, and cleaning, fan bearing lubrication, and belt adjustment are all examples of routine maintenance that must be performed.
• Blower and motor assemblies and coil and filter sections are always provided with a service door or panel for proper component access. Clearances for component removal may be greater than the service clearances.
• Refer to the submittal drawings for these clearance dimensions.

Additional Clearances for Packaged DX Units

• Packaged DX units require additional service clearance because they must have unrestricted air movement around the condenser coil and condenser fans.
• Hot air is being discharged from the condenser fans during operation and the more clearance available, the better, as this avoids the chance of recirculation or coil starvation.
• This unit should never be placed under an overhang or inside a building.
• A minimum of 48 inches above the condenser fans is recommended.

Lifting

• All units equipped with this module are provided with either four or six lifting lugs. When the unit is being hoisted, all of the provided lugs must be used for support. Four lifting lugs are on the four corners of the unit, located at the base.
• In addition, there may be two more lifting lugs located at the top of the unit. The locations of those two top lugs vary somewhat from unit to unit.
• Use spreader bars as shown to prevent damage to the cabinet. If top‑mounted lifting lugs are present, they must be used in conjunction with the bottom‑mounted lifting lugs when hoisting the unit.

Install Condensate Drain (P Trap)

• The only installation step that is specific to the DX module is the installation and priming of the engineered P trap. Locate the
• P trap kit that was shipped with the unit and install the kit under the enclosed instructions.

Provide and Install Switch S4

Each Packaged DX unit requires a contact closure to enable the unit to run. This can be a user‑supplied switch that may be a toggle switch mounted in a 2 x 4-inch electrical box (mounted in a position chosen by the user), or it may be a simple jumper or even a control switch installed in a remote control panel supplied by the factory. See also “Additional Control Components” on page 5 of this manual.

Component Operation

Each Packaged DX module has a complete set of compressor contactors, condenser fan contactors, relays, and certain integral safety controls located in the module.

Electrical Components

1. Compressor Relays
2. Condenser Fan Contactor
3. A. Compressor Contactor (Circuit A)
   • B. Compressor Contactor (Circuit B) (not shown)
4. Low Voltage Terminal Strip
5. Optional Digital Scroll Controller
   • Refrigerant Components
6. A. Compressor (Circuit A)
   • B. Compressor (Circuit B)
7. A. High Pressure Sensor (Circuit A, Manual Reset) (not shown)
   • B. High Pressure Sensor (Circuit B, Manual Reset) (not shown)
8. A. Thermostatic Expansion Valve (TXV) (Circuit A)
   • B. Thermostatic Expansion Valve (TXV) (Circuit B)
9. A. Refrigerant Distributor (Circuit A)
   • B. Refrigerant Distributor (Circuit B)
10. Condensate Drain (P trap here)
11. Hot gas bypass valve ‑ optional (not shown)

Additional Control Components

In addition to the control components located in the PDX module, various high- and low-voltage circuits are found in the make-up air unit control center. See the unit-specific wiring diagram (found in the unit control center) for complete information.

1. Power Distribution Block – field-supplied power from the main disconnect switch is terminated here.
2. Phase Monitor has jumpers going to the power distribution block). Constantly checks for loss of a phase or phase reversal. Requires 24 VAC to operate. When a fault is detected, it cuts off the power supply to the low-voltage terminal strip, disabling all motors. It has one red LED indicator light. Constant “ON” indicates properly applied power, If the LED is flashing, this indicates a “fault” connection.
3. The transformer provides 24 VAC to various low-voltage devices including the Phase Monitor and Low Voltage Terminal Strip in the compressor compartment.
4. Relays RC1 and RC2 are wired to the control center in the compressor compartment.
5. Low Voltage Terminal Strip – Switch S4 terminates here.
6. Thermostat (Inlet Air Sensor) – TS5 monitors outdoor air temperature. It is field-adjustable. If there is more than one cooling circuit, an additional controller for the second stage will be provided. The TS5 will turn the DX cooling stages on or off.
7. Dirty Filter Switch – optional air proving switch and it is field-adjustable to monitor filter loading.

Optional Digital Scroll Compressors Standard with Electronically Commutated (EC) Condenser Fans

• The EC condenser fan will modulate up and down to maintain the highest liquid line pressure. The factory set points are: Set (left dial): 23 barg; Diff (right dial): 5 barg.
• Fan operations with these set points are as follows.
• The fan will be at max speed (~1140 rpm) when the highest liquid line saturation temperature is 118°F (410 psig, 28 barg).
• The fan remains at max speed if the pressure is higher than 410 psig (28 barg). The fan will be at min speed (~180 rpm) when the highest liquid line saturation temperature is 105°F (340 psig, 23 barg).
• Below this pressure, the fan will be off. The fan modulates linearly between the min and max speeds.

Factory-Installed Refrigeration System Components

1. Thermostatic Expansion Valve (TXV)
   • Each unit is equipped with a Thermal Expansion Valve on each refrigerant circuit. The valve controls the flow of liquid refrigerant entering the evaporator coil by maintaining a constant, factory-set superheat of 10°F. The valve is adjustable and is located on the side of the evaporator coil and can be accessed through the coil panel access door.
2. Refrigerant Distributor
   • Attached to the TXV is a refrigerant distributor.
   • The refrigerant distributor evenly distributes the refrigerant to each circuit of the evaporator coil to provide optimum performance.
3. Evaporator Coil
   • The coil is located in the supply airstream. In the DX system, the liquid refrigerant is expanded in the TXV and it then flows through the evaporator coil. The refrigerant enters the coil as a low-temperature liquid/gas where it eventually boils into a low-temperature, low-pressure gas before going into the compressor. As the refrigerant passes through the evaporator coil, it absorbs heat from the airstream. To ensure proper operation, the coil surface must be cleaned so that air movement over the coil provides the necessary heat transfer.
4. Low Limit Pressure Switch
   • The switch is installed in the suction line and disables the DX system when the suction pressure drops below the set point. The switch will auto-reset when the pressure rises above the auto-reset set point.
5. Compressors
6. Condensing Coil
7. Condenser Fans
8. High Limit Pressure Switch
   • The switch opens when refrigerant pressure increases above the set point in the liquid line and it then requires a manual reset.
9. Liquid Line Filter-Drier
   • The liquid line filter-drier prevents moisture and foreign matter from entering the expansion valve.
10. Moisture Indicating Sight Glass
    • During normal operating conditions, the sight glass should typically be liquid. Some gas is acceptable, but excessive bubbles may indicate an improper charge or a leak in the system. The center dot indicates the moisture level in the refrigerant. A pink dot indicates moisture and needs to be dealt with. A blue dot indicates a dry system. A purple dot indicates caution − there may be moisture above 50 ppm in the system.
11. Access Ports
12. Hot Gas Bypass Manual Shut Off Valve (optional)
    • Used to disable hot gas bypass for service and troubleshooting procedures.
13. Hot Gas Bypass Valve (optional)
    • On units equipped with hot gas bypass, hot gas from the compressor is injected into the liquid line of the evaporator coil after the TXV.
    • Valve Adjustment – To adjust the valve, connect a pressure gauge to the suction line and block the entering air to the evaporator coil. The valve should begin to open when the suction pressure drops to approximately 115 PSIG for R-410A (the valve will feel warm to the touch). Adjustments are made by first removing the cap on the bottom of the valve and then turning the adjusting stem clockwise to increase the setting pressure (counterclockwise to decrease).
    • Allow several minutes between adjustments for the system to stabilize. When adjustment is complete, replace the cap on the valve.
14. Pressure Gauge & Transducer (Optional digital scroll compressor Standard with EC condenser fans only)
    • See Optional Electronically Commutated (EC) Condenser Fans under the component operation.

Sequence of Operation without Microprocessor Controller

• The compressors are energized by an outdoor air thermostat TS5, located in the unit control center.
• The thermostat sensor is located in the intake airstream upstream of the DX coil. The thermostat can be a single or dual-stage thermostat depending on the number of compressors.
• The factory settings for the thermostat vary based on the model and are field adjustable.

80ºF

|

5ºF

|

10ºF

• The first stage of cooling will energize when the outdoor air temperature rises above the thermostat set point plus the differential.
• The second stage of cooling will energize when the outdoor air temperature rises above the second stage offset plus the differential.

Control Sequence

1. The fan switch needs to be closed (S3) between terminals R and G.
2. Heating/Cooling switch (S4) is closed between terminal R and Y1.
3. N.O. contact on the fan relay (RF) is energized and closed.
4. When the outdoor air temperature is above the set point the differential power passes through N.O. contacts on the outdoor air thermostat (TS5) and energizes the cooling relay (RC1).
5. When the pressure switches LPS (refrigerant low-pressure switch) and HPS (refrigerant high-pressure switch) are in their normal state relay R10 will energize. Starting the first stage compressor contactor.
6. When the outdoor air temperature is above the second stage offset the differential power passes through N.O. contacts on the outdoor air thermostat (TS5) and energizes the cooling relay (RC2).
7. When the pressure switches LPS and HPS (refrigerant high-pressure switch) are in their normal state relay R11 will energize, starting the second stage compressor contactor.

Control Sequence – Two Circuit Variable Air Volume (optional)

1. The fan switch needs to be closed (S3) between terminals R and G.
2. Heating/Cooling switch (S4) is closed between terminal R and Y1.
3. N.O. contact on the fan relay (RF) is energized and closed.
4. When the outdoor air temperature is above the set point the differential power passes through N.O. contacts on the outdoor air thermostat (TS5) and energizes the cooling relay (RC1).
5. When the pressure switches LPS (refrigerant low pressure switch) and HPS (refrigerant high-pressure switch) are in their normal state relay R10 will energize. Starting the first stage compressor contactor.
6. When the outdoor air temperature is above the second stage offset the differential power passes through N.O. contacts on the outdoor air thermostat (TS5) and energizes the cooling relay (RC2).
7. When the pressure switches LPS (refrigerant low-pressure switch) and HPS (refrigerant high-pressure switch) are in their normal state relay R11 will energize, starting the second stage compressor contactor.
8. When the discharge air temperature drops below the low-temperature set point (TS9) factory set at 55°F, the second-stage compressor contactor will reenergize, turning off the second-stage compressor.
9. The second stage compressor will re-energize when the discharge air temperature rises above 75°F.

Control Sequence – Single Circuit with Optional Hot Gas Bypass

1. The fan switch needs to be closed (S3) between terminals R and G.
2. Heating/Cooling switch (S4) is closed between terminal R and Y1.
3. N.O. contact on the fan relay (RF) is energized and closed.
4. When the outdoor air temperature is above the set point the differential power passes through N.O. contacts on the outdoor air thermostat (TS5) and energizes the cooling relay (RC1).
5. When the pressure switches LPS (refrigerant low-pressure switch) and HPS (refrigerant high-pressure switch) are in their normal state relay R10 will energize. Starting the first stage compressor contactor.
6. When the suction gas temperature falls below 28ºF, which is 32-34ºF coil surface temperature, the hot gas bypass valve opens injecting hot gas from the compressor into the liquid line of the evaporator coil.

Sequence of Operation with Optional Microprocessor Controller

• If the unit is equipped with a microprocessor controller it will be located in the unit’s main control center.

NOTE

• Similar Carel hardware is used for the network interfacing and indirect furnace control options. Only the microprocessor controller will contain keypad buttons on both the left and right sides of the display.
• For any other hardware, please reference the previous section Sequence of Operation without the Optional Microprocessor.
• If the unit is equipped with a microprocessor controller it will be located in the unit’s main control center.
• With a microprocessor controller, the compressors will be energized by the microprocessor.
• When the outside air temperature rises above the cooling lockout temperature set point (plus the differential), the microprocessor will energize the cooling stages as required to maintain the supply temperature set point.
• The cooling lockout temperature set point is factory set to 80ºF with a 2ºF differential. The supply temperature set point is factory set to 70ºF.
• The set points and cooling lockout differential are field-adjustable using the microprocessor keypad. For additional information on the microprocessor controller, please reference the
• Microprocessor Controller Installation, Operation and Maintenance Manual.

Start-Up Unit

• DANGER Electric shock hazard. Can cause injury or death. Before attempting to perform any service or maintenance, turn the electrical power to the unit to OFF at the disconnect switch(es). The unit may have multiple power supplies.
• CAUTION Use caution when removing access panels or other unit components, especially while standing on a ladder or other potentially unsteady base. Access panels and unit components can be heavy and serious injury may occur.
• CAUTION Do not operate without the filters and birdscreens installed. They prevent the entry of foreign objects such as leaves, birds, etc.
• CAUTION Do not run the unit during the construction phase. Damage to internal components may result in and void warranty.

WARNING

• The unit was factory-tested. All blowers, fans, and compressors are set up to run correctly when supplied power. If any fan is running backward or the compressor is making loud noises, immediately turn off the power. Switch two leads on the incoming power to the disconnect. This will ensure the proper operation of the unit. Failure to comply may damage the compressors and void the warranty.
• Do not jump any safety devices when operating the unit. This may damage components within or cause serious injury or death.
• Do not operate the compressor when the outdoor temperature is below 40ºF.
• Do not short-cycle the compressor. Allow 5 minutes between “on” cycles to prevent compressor damage.
• A DX system is charged with refrigerant. A start-up must be performed by a certified Technician.
• WARNING Prior to starting up the unit, power must be energized for 24 hours without a call for cool to allow the compressor crankcase heaters time to boil off any liquid refrigerant present in the compressor.
• Every installation requires a comprehensive start-up to ensure the proper operation of the unit. As part of that process, the following checklist must be completed and information recorded. Starting up the unit under this checklist will not only ensure proper operation but will also provide valuable information to personnel performing future maintenance. Should an issue arise that requires factory assistance, this completed document will allow unit experts to provide quicker resolution.
• Qualified personnel should perform start-up to ensure safe and proper practices are followed.
• Unit Model No. _ ___
• Unit Serial No. _____
• Compressor 1 Model No. _ __
• Compressor 2 Model No. _ __
• Start-Up Date _ ____
• Start-Up Personnel Name ___
• Start-Up Company _ ____
• Phone Number _ ___

Pre-Start-Up Checklist

• Disconnect and lock out all power switches.
• Remove any foreign objects that are located in the unit.
• Check all fasteners, set screws, and locking collars on the fans, bearings, drives, motor bases, and accessories for tightness.
• Rotate the fan wheels by hand and ensure no parts are rubbing.
• Filters can load up with dirt during building construction. Replace any dirty pleated filters and clean the aluminum mesh filters in the intake hood.
• Verify that non-motorized dampers open and close properly.
• Check the tightness of all factory wiring connections.
• Verify control wire gauge.
• Verify proper drain trap installation.
• Check condensing fans for any damage or misalignment. Spin the blades and make sure they don’t contact any parts and are free-turning without any resistance.
• Look over the piping system.
• Inspect all coils within the unit. Fins may get damaged in transit or during construction. Carefully straighten fins with a fin comb.
• If there is an indirect gas-fired furnace in this unit, refer to the manual provided with this unit for Pre-Start-Up information.
• This unit contains a crankcase heater for each compressor which needs power supplied to it 24 hours before start-up. If the start-up is scheduled in 24 hours, unlock the disconnect power and energize the unit.

SPECIAL TOOLS REQUIRED

• Voltage Meter (with wire probes)
• Amperage Meter
• Pressure Gauges – (refrigerant)
• Tachometer
• Thermometer
• Incline manometer or equivalent

Start-Up Procedure

• The unit will be in operational mode during start-up. Use necessary precautions to avoid injury. All data must be collected while the unit is running.
• Ensure the Pre-Start-Up checklist is complete.
• Jumper R to G, R to Y1, and R to Y2 (if applicable) on the control board.
• Turn the disconnect on. After 3 minutes compressors will come on. Make sure all fans and compressors are rotating in the correct direction.
• Allow the unit to run until the refrigerant system stabilizes. Approximately 5-10 minutes.

Voltage Imbalance

• In a 3-phase system, excessive voltage imbalance between phases will cause motors to overheat and eventually fail. The maximum allowable imbalance is 2%.
• To determine voltage imbalance, use recorded voltage measurements in this formula.
• Key: V1, V2, V3 = line voltages as measured
• VA (average) = (V1 + V2 + V3) \ 3
• VD = Line voltage (V1, V2 or V3) that deviates farthest from average (VA)
• Formula: % Voltage Imbalance = [100 x (VA-VD)] \ VA

Start-Up Checklist

Troubleshooting – Alarms

Optional Digital Scroll Compressor Controller

• Present only if packaged DX with digital scroll option is selected. The controller has three LED indicator lights.
• One is green, indicating that it has power, one is an alarm indicator that will flash a code for various alarm conditions and the third indicates whether the compressor is operating in a loaded or unloaded condition.
• See the manufacturer’s unit-specific manual for further information.
• See the Fault Code chart. The Fault Code chart is also printed on the back of the controller.
• Note that if the controller generates either a Code 2 or a Code 4 Lockout, a manual reset must be performed. Manual Reset is accomplished by shutting off the main power to the unit and then turning it back on.

Digital Scroll Compressor Controller Fault Codes

Alert Code| System Condition| Diagnostic Alert Light| Action
Code 2| High Discharge Temperature Trip| Blinks 2 Times| Lockout
Code 3| Compressor Protector Trip| Blinks 3 Times| Lockout
Code 4| Locked Rotor| Blinks 4 Times| Lockout
Code 5| Demand Signal Loss| Blinks 5 Times| Lockout
Code 6| Discharge Thermistor Fault| Blinks 6 Times| Reduce Capacity
Code 7| Future| N/A| N/A
Code 8| Welded Contactor| Blinks 8 Times| Unload Compressor
Code 9| Low Voltage| Blinks 9 Times| Trip Compressor

Protective faults that require manual reset.

Troubleshooting – Refrigeration Circuit

TROUBLESHOOTING NOTE

• Before any components are changed in the refrigeration system, the cause of the failure must be determined.
• Further problems will exist unless the true cause or problem is identified and corrected.

IMPORTANT

• Do not release refrigerant into the atmosphere! If required service procedures include the adding or removing of refrigerant, the service technician must comply with all federal, state, and local laws.
• The procedures discussed in this manual should only be performed by a qualified EPA Certified Technician.
• NOTE: The unit is equipped with a phase loss/phase reversal control. If a system does not start, check the phase of the electrical supply.
• The first step is to check airflow conditions. (e.g. improper ductwork, atypical wet bulb / dry bulb, etc.) After these steps have been eliminated, proceed with troubleshooting by following this guide:

Always have a completed Pre-Start-Up Checklist and Start-Up Checklist before requesting parts or service information.

The compressor starts but cuts out

on high-pressure switch

High pressure activates at 600 PSIG

| Refrigerant overcharge.| Check pressures, and charge by subcooling.
The condenser fan motor is defective.| Check the fan motor.
Condenser coil inlet obstructed or dirty.| Check coil and clearances. Clean coil if necessary.
Air or non‑condensables in system.| Check high-side equalized pressures, and check thermal expansion valves.
Defective high-pressure switch.| Replace.
Restriction in discharge or liquid line.| Check refrigerant line pressures, check thermal expansion valves, and replace any defective components.
The condensing fan relay not pulling in.| Replace.
Compressor cuts out on thermal overload| Low voltage.| Check voltage.
Sustained high discharge pressure.| Check running amperage and conditions described under “low suction pressure” symptoms.
High suction and discharge pressures.| Check the thermal expansion valve setting, and check for air in the system. Check air conditions and cfm.
Defective compressor overload.| If the compressor is hot, allow the compressor to cool for two hours. Recheck for open circuit.
Improper refrigerant charge.| Check subcooling.
Improperly wired.| Review wiring schematics.
Loose wiring.| Check all connections.
Defective start relay.| Replace relay.
Motor windings damaged.| Verify amp draw.
The compressor hums, but will not start| Improperly wired.| Review wiring schematics.
Low line voltage.| Check voltage.
Loose wiring.| Check all connections.
Defective start relay.| Replace relay.
Motor winding damaged.| Verify amp draws. Replace the compressor if necessary.
Internal compressor mechanical damage.| Replace.
Compressor noise or vibrating| Refrigerant overcharge.| Check pressures and subcooling.
Liquid floodback.| Check the thermal expansion valve setting. Check for refrigerant overcharge.
Tubing rattle.| Dampen tubing vibration by taping or clamping. Carefully bend the tubing away from contact where possible.
Scroll compressor rotating in reverse. (3‑phase)| Check high and low side pressures during operation to confirm. Rewire for opposite rotation.
Damaged compressor.| Replace the compressor.
Improper mounting on unit base.| Check that the compressor is properly isolated and that the mounting bolts are tight.

Always have a completed Pre-Start-Up Checklist and Start-Up Checklist before requesting parts or service information.

entering wet bulb temperature, and check for excessive airflow.
The compressor is unloaded. (digital scroll)| Check the digital scroll controller signal and solenoid valve.
The expansion valve sensing bulb is not secured to the suction line.| Check the thermal expansion valve, and ensure the bulb is insulated. Check to superheat. If the superheat is high, then the valve is choking refrigerant flow.

• Check bulb for contact.

• Adjust valve for superheat ~10°F.

• Replace valve power head or valve.

Thermostatic expansion valve. Overfeeding.| Check bulb location and clamping. Adjust superheat. Replace the expansion valve power head.
The room load is too large.| Reduce the load or add more equipment.
Overcharged.| Check pressures and subcooling.
High discharge pressure| Thermal expansion valve setting.| Check the thermal expansion setting and calibrate superheat / subcooling.
Air inlet to condenser dirty or obstructed.| Check for proper clearances and possible air recirculation. Clean coil.
The condenser fan motor is defective.| Check the condenser fan motor.
Too much refrigerant.| Check subcooling. Remove excess refrigerant.
Non‑condensable in system.| Remove non‑condensable from the system.
Dirty condenser coil.| Clean condenser coil.
The condenser fan not running or running backward.| Check the electrical circuit and fuse. Check fan cycling controls.
High load conditions.| Add more equipment or reduce load.
Low suction pressure| Refrigerant undercharge/loss of refrigerant charge.| Check pressures and subcooling.
The blower running backward.| Confirm blower rotation. If reversed, interchange any two wires from the 3‑phase disconnect.
Loose blower, pulley, or belts.| Check drive pulley alignment and belt tension.
Low entering air temperature. (Low load conditions).| Check to enter air-wet bulb conditions.
Refrigerant leak.| Check the system for leaks. Repair leaks and add refrigerant.
Evaporator dirty or iced‑up, or airflow restricted.| Clean the coil. Check fan operation. Check airflow.
Plugged liquid line filter‑drier.| Replace the filter‑drier, and check the psi across the filter.
Improper hot gas bypass setting.| Check settings and correct them as required.
Expansion valve defective, superheat too high, or valve too small.| Adjust the valve for proper superheating or replace the expansion valve if too small or defective.
Moisture in the system, check sight glass.| Reclaim refrigerant, check for leaks, and recharge.

Always have a completed Pre-Start-Up Checklist and Start-Up Checklist before requesting parts or service information.

and check for leaks. Repair the leak and add refrigerant.
Defective or improperly adjusted expansion valve.| Check to superheat and adjust the thermal expansion valve.
Low suction pressure.| See “low suction pressure”.
Faulty condenser temperature controls. (Condensing fan cycle switch).| Check condenser controls and reset to obtain the desired condensing temperature.
Compressor short cycles| Thermostat location or controls malfunction.| Check the thermostat, and check heat anticipator settings.
Improper refrigerant charge.| Check subcooling, and verify superheat.
Defective high or low-pressure control.| Check the high or low-pressure switch.
Poor air distribution.| Check ductwork for recirculation.
High discharge pressure.| See “high discharge pressure” in Troubleshooting section.
Low airflow at evaporator(s).| Check blower operation and airstream restrictions.
Incorrect unit selection (oversized).| Contact factory.
Compressor loses oil| Refrigerant leak.| Check the system for leaks. Repair leaks and add refrigerant.
Short cycling.| Check low-pressure control settings.
Refrigerant floodback.| Check the thermal expansion valve setting. Check for refrigerant overcharge. Check crankcase heater operation.
Not enough cooling

or lack of cooling

| Refrigeration undercharged.| Check subcooling. Adjust the charge, if necessary.
A dirty filter or evaporator coil.| Check filter, coil, and airflow.
Dirty or clogged condenser coil.| Check coil and airflow.
Air or other non‑condensables in the system.| Check equalized high-side pressure with equivalent outdoor temperature.
Restriction in suction and liquid line.| Check for restrictions in the refrigerant circuit.
Control contacts are stuck.| Check wiring.
Excessive load.| Add more equipment or reduce room load.
The liquid line is frosted or wet| Restriction in liquid line.| Clear restriction upstream of the point of frosting.
The suction line is frosting| Insufficient evaporator airflow.| Check airflow, check filters, and check the drive for loose parts or belts. Check the VFD control signal for proper operation.
Malfunctioning or defective expansion valve.| Check the bulb of the thermal expansion valve.
Frost on the evaporator coil| The hot gas bypass valve not functioning properly.| Check valve. If defective, replace.
Manual hot gas bypass valve closed.| Open valve.
Low load or airflow.| Increase airflow, and check filters.

Always have a completed Pre-Start-Up Checklist and Start-Up Checklist before requesting parts or service information

Routine Maintenance

DANGER

• Electric shock hazard. Can cause injury or death.
• Before attempting to perform any service or maintenance, turn the electrical power to the unit to OFF at the disconnect switch(es). A unit may have multiple power supplies.

CAUTION

• Use caution when removing access panels or other unit components, especially while standing on a ladder or other potentially unsteady base. Access panels and unit components can be heavy and serious injury may occur.
• This unit requires minimal maintenance to operate properly. To ensure proper operation and longevity, the following maintenance schedule should be followed.
• The items in this list assume a relatively clean-air environment and may require attention more frequently in dusty or dirty areas.
• If this unit contains an indirect gas-fired heater, refer to the Installation, Operation, and Maintenance manual provided with the unit for maintenance purposes.
• An EPA Certified Technician should complete all refrigeration systems checks.

Maintenance Frequency: Monthly

1. Condensate Drain Inspect and Clean. Refill with water or glycol.

Annually

• It is recommended that the annual inspection and maintenance occur at the start of the cooling season.
• After completing the checklist, follow the unit start‑up checklist provided in the manual to ensure the refrigeration system operates in the intended manner.

1. Door Seal
   • Check if intact and pliable.
2. Wiring Connections
   • Check all connections for tightness.
3. Cabinet
   • Check the entire cabinet, inside and out, for dirt build-up or corrosion. Remove accumulated dirt, remove any surface corrosion, and coat the area with an appropriate finish.
4. Evaporator Coil Maintenance
   • Check for cleanliness. Clean if required.
5. Condenser Coil Maintenance
   • Check for cleanliness. Clean if required.
6. Condensate Drain
   • Inspect and clean. Refill with water.
7. Condensing Fan Blades and Motors
   • Check for cleanliness.
   • Check all fasteners for tightness.
   • Check for fatigue, corrosion, and wear.

Maintenance Procedures: Lubrication

• Check all moving components for proper lubrication.
• Apply lubricant where required. Any components showing excessive wear should be replaced to maintain the integrity of the unit and ensure proper operation.

Dampers

• Check damper (if present) to ensure it opens and closes properly and without binding. Apply power to motorized dampers to ensure the actuator opens and closes the damper as designed.

Reference

Component Location

Maintenance Log

Our Commitment

• As a result of our commitment to continuous improvement, Accurex reserves the right to change specifications without notice.
• Product warranties can be found online at accurex.com, either on the specific product page or in the Warranty section of the website at Accurex.com/Resources/Warranty.
• P.O. Box 410 Schofield, WI 54476
• Phone: 800.333.1400
• Fax: 715.241.6191
• Parts: 800.355.5354
• accurex.com
• 474891 Packaged DX Module for Make-Up Air, Rev. 6, April 2024 © 2024 Accurex, LLC

Documents / Resources

| ACCUREX 474891 Packaged DX Module [pdf] Installation Guide
474891, 474891 Packaged DX Module, Packaged DX Module, DX Module, Module
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References

• Accurex | Commercial Kitchen Ventilation Systems

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