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SERVICE MANUAL
A80US2VX Gas Furnace
This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to
the potential for personal injury or death.
A80US2VX
series
units
furnaces used for upflow or horizontal applications only,
manufactured with heat exchangers formed of aluminized
steel. A80US2VX units are available in heating capacities
of 40,000 to 100,000 Btuh and cooling applications up to
5 tons. Refer to Engineering Handbook for proper sizing.
Units are approved for installations up 7500 ft and factory
equipped for use with natural gas only. A80US2VX model
units are equipped with the Comfort Sync
SureLight
two-stage variable speed integrated control.
®
A80US2VX unit meets the California Nitrogen Oxides
(NOx) Standards and California Seasonal Efficiency
requirements. All units use a redundant gas valve to assure
safety shut-off as required by C.S.A.
All specifications in this manual are subject to change.
Procedures outlined in this manual are presented as a
recommendation only and do not supersede or replace
local or state codes. In the absence of local or state codes,
the guidelines and procedures outlined in this manual
(except where noted) are recommendations only and do
not constitute code.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer or
equivalent, service agency, or the gas supplier.
508033-02
are
80%
efficiency
®
WARNING
gas
Technical Specifications ..............................................2
Blower Performance ....................................................3
Parts Arrangement.......................................................5
Unit Components .........................................................6
Indoor Blower Motor ..................................................20
Heating Components .................................................24
Placement and Installation ........................................27
enabled
Start-Up .....................................................................27
Heating System Service Checks ...............................28
High Altitude ..............................................................30
Typical Operating Characteristics ..............................31
Maintenance ..............................................................32
Wiring and Sequence of Operation ...........................34
Program Unit Capacity Size Modes...........................43
Troubleshooting .........................................................44
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves
and protective clothing.
Issue 2135
Table of Contents
CAUTION
*P508033-02*
(P) 508033-02
Page 1 of 48

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Summary of Contents for Allied A80US2VX

  • Page 1 Unit Components ............6 Indoor Blower Motor ..........20 Units are approved for installations up 7500 ft and factory Heating Components ..........24 equipped for use with natural gas only. A80US2VX model Placement and Installation ........27 units are equipped with the Comfort Sync enabled ®...
  • Page 2 Technical Specifications Physical and Electrical Data Max. Time Approx Nominal Volts/ Nominal Input Output AFUE Delay Trans Shipping Model Cooling Inlet Full Load (Btuh) (Btuh) (ICS) Breaker or (VA) Weight Capacity (in.) Phase Amps Fuse (lbs) A80US2V060A12X 60,000 48,000 3 Tons 120-60-1 A80US2V080B16X 80,000...
  • Page 3 Blower Performance A80US2V060A12X BLOWER PERFORMANCE (less filter) BOTTOM RETURN AIR 0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range HEATING Heating Speed DIP First Stage Heating Speed - cfm Second Stage Heating Speed - cfm Switch Settings +24% 1030...
  • Page 4 A80US2V080C20X BLOWER PERFORMANCE (less filter) BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE 0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range HEATING Heating Speed DIP First Stage Heating Speed - cfm Second Stage Heating Speed - cfm Switch Settings...
  • Page 5 Parts Arrangement Heat Exchanger Combustion Air Inducer Gas Valve Air Intake Pipe Inner Access Control Box Access Panel Panel (includes two-stage integrated control, transformer and circuit breaker) Blower Assembly Figure 1. 508033-02 Issue 2135 Page 5 of 48...
  • Page 6 A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the transformer A80US2VX unit components are shown in Figure 1. (T1). The breaker is rated 3A at 32V. If the current exceeds The gas valve, combustion air inducer and burners can this limit the breaker will trip and all unit operation will be accessed by removing the access panel.
  • Page 7 Electronic Ignition While in the two-stage thermostat mode (two DIP switch setting) the burners will fire on first-stage heat. The At the beginning of the heat cycle the integrated control combustion air inducer will operate on low speed and monitors the first stage and second stage combustion air indoor blower will operate on low heat speed.
  • Page 8 HS/ CAI LINE 1 NEUTRAL 7 SEGMENT LED FLAME SENSE INDOOR BLOWER DIAGNOSTIC CONNECTOR PUSH BUTTON DIP SWITCHES 12 PIN LOW OUTDOOR AIR VOLTAGE SENSOR CONNECTOR TERMINALS DISCHARGE AIR W915 Y1 TO Y2 SENSOR 2 STAGE COMPR TERMINALS W951 R TO O HEAT PUMP TB83 COMMUNICATING...
  • Page 9 INTEGRATED CONTROL CONFIGURATION GUIDE CLG BLOWER SPEED ADJUSTMENT 2ND STAGE HEAT ON DELAY DEFAULT 7 MIN CONTINUOUS FAN MODE BLOWER SPEED UPSTAGE THERMOSTAT SELECTION DELAY + 10% MEDIUM−LOW SPEED TWO STAGE (38%) THERMOSTAT 12 MIN − 10% UPSTAGE MEDIUM−HIGH DELAY SPEED 1−STAGE (70%)
  • Page 10 Display Action (when button released) No change (idle)* Remain in idle mode Solid “E” Enter diagnostic recall mode Solid “D” Discharge Air Installed Solid “F” Enter flame signal mode Solid “P” (variable speed only) Program unit capacity/size (Unit Code) Two horizontal bars = Soft disable * No change implies the display will continue to show whatever is currently being displayed for normal operation (blinking decimal, active error code, heat state, etc..)
  • Page 11 Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover Idle mode (Decimal blinks at 1 Hertz -- 0.5 second ON, 0.5 second OFF). Cubic feet per minute (cfm) setting for indoor blower (1 second ON, 0.5 second OFF) / cfm setting for current mode displayed.
  • Page 12 Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E124 Active communicating thermostat signal Equipment lost communication with the thermostat. Check four wiring missing for more than 3 minutes. connections, ohm wires and cycle power at the thermostat. Alert stops all services and waits for heartbeat message from thermostat (subnet controller).
  • Page 13 Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E223 Low pressure switch failed open. Check pressure (inches w.c.) of low pressure switch closing on heat call. Measure operating pressure (inches w.c.). Inspect vent and combustion air inducer for correct operation and restriction. Resumes normal operation after fault is cleared E224 Low pressure switch failed closed.
  • Page 14 Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E274 Soft lockout - Exceeded maximum number Shut down system. 1-hour soft lockout. Check firing rate and air flow. Check of recycles. Last recycle failed due to the for blockage. Clears when heat call finishes successfully. limit circuit opening or limit remained open longer than 3 minutes E275...
  • Page 15 Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E348 No 24 Volt output on Y2 of ”integrated Y2 relay / Stage 2 failed. (Pilot relay contacts did not close or the relay coil control” with non?communicating outdoor did not energize;...
  • Page 16 DIP Switch Settings Indoor Blower Operation DIP Switch Settings NOTE: All Comfort Sync settings are set at the Comfort ® Switches 5 and 6 -- Cooling Mode Blower Speed -- Sync Wi-Fi thermostat. See Comfort Sync installation ® ® ® The unit is shipped from the factory with the dip switches instruction.
  • Page 17 Ramping Option A (Factory Selection) Switches 11, 12 and 13 -- Heating Mode Blower Speed The switches are factory set to the OFF position which • Motor runs at 50% for 30 seconds. provides factory default heat speed. Refer to Table 10 for •...
  • Page 18 *Dehumidification blower speed is 70% of COOL speed for all units. **In Precision mode, thermostat will maintain room temperature up to 2 °F (1.2°C) cooler than room setting. Table 12. Operating Sequence A80US2VX, Non-Communicating Thermostat with Humidity Control Feature and Single-Speed Outdoor Unit Page 18 of 48 Issue 2135...
  • Page 19 **Dehumidification blower speed is, reduced to 70% of COOL. ***In Precision mode, thermostat will maintain room temperature up to 2 °F (1.2°C) cooler than room setting. Table 13. Operating Sequence A80US2VX, Non-Communicating Thermostat with Humidity Control Feature and Two-Speed Outdoor Unit 508033-02 Issue 2135...
  • Page 20 Then Slide Out Front of Unit. in sequence, the rotor shaft turns the blower. Figure 6. All A80US2VX blower motors use single phase power. An external run capacitor is not used. The motor uses permanently lubricated ball-type bearings. WARNING...
  • Page 21 Failure to wait may cause personal injury or death. Power Choke (L13) A choke coil is used on A80US2VX 4 and 5 ton units equipped with 1 hp motors. The choke is located on the blower housing and is used to suppress transient current spikes.
  • Page 22 BLOWER B3 HARNESS CONNECTORS BLOWER B3 HARNESS CONNECTORS P48 5 Pin P49 4 Pin P48 5 Pin SHAFT SHAFT P49 4 Pin MOTOR with INTEGRATED MOTOR with INTEGRATED CONTROLLER CONTROLLER J48 5 Pin P48 5 Pin J49 4 Pin P49 4 Pin J49 4 Pin Control Connector J48 5 Pin Line Voltage Connector J48 Connector...
  • Page 23 Troubleshooting Motor Windings TEST A Ensure that motor windings are not damaged by performing Measure the resistance between each of the three motor the following tests: leads (3-pin plug) and the unpainted part of the end shield. NOTE: If your ohm meter is not an auto-ranging type, set If the winding resistance to ground is <100k ohms, it to the highest ohm scale (100k ohms or greater) before replace the motor and control module.
  • Page 24 Figure 14 for ignitor check out. operate the unit with air gas plenum in place. The burner NOTE: The A80US2VX furnace contains electronic has one orifice located between the gas valve and the components that are polarity sensitive. Make sure that the air intake assembly (Figure 13).
  • Page 25 HEATING COMPONENTS Air Gas Plenum Burner Gasket Gas Valve Sensor Ignitor Orifice Housing Gas Orifice Air Orifice Intake Air Screen Thermal Intake Air Switch Elbow (location) Figure 13. 508033-02 Issue 2135 Page 25 of 48...
  • Page 26 Ignitor Check Out (exploded view for clarity) Test 1 Remove 5-pin plug from control Check ohms reading across terminals 1and 5 Ohm value should be between 39 - 70. Meter (set to ohms) Integrated control detail Test 2 Seperate the 2-pin jack plug near the manifold and check resistance of the ignitor.
  • Page 27 Combustion Air Inducer (B6) Placement and Installation All A80US2VX units use a two-stage combustion air inducer to move air through the burners and heat exchanger during Make sure unit is installed in accordance with installation heating operation. The blower uses a 120VAC motor.
  • Page 28 CSA Certification Figure 16. All units are CSA design certified without modifications. Replace the access panel. Refer to the A80US2VX Installation Instruction. 10. Turn on all electrical power to to the unit. Gas Piping 11. Set the thermostat to desired setting.
  • Page 29 Table 17 shows acceptable Do not use matches, candles, flame or any other combustion for ALL A80US2VX models. The maximum source of ignition to check for gas leaks. carbon monoxide reading should not exceed 100 ppm.
  • Page 30 Proper Gas Flow (Approximate) High Altitude Furnace should operate at least 5 minutes before checking Units may be installed at altitudes up to 7,500 ft. above gas flow. Determine time in seconds for two revolutions of sea level. See Table 18 for de-rate manifold values. Units gas through the meter.
  • Page 31 0.8” W.C. Temperature Rise Figure 18 Seal the hole when the check is complete. Temperature rise for A80US2VX units depends on unit input, blower speed, blower horsepower and static pressure as marked on the unit rating plate. The blower...
  • Page 32 Check the cleanliness of blower assembly and Maintenance clean the housing, blower wheel and blower motor if necessary. The blower motors are prelubricated for Annual Furnace Maintenance extended bearing life. No further lubrication is needed. At the beginning of each heating season, and to comply Inspect the combustion air inducer and clean if with the Limited Warranty, your system should be checked necessary.
  • Page 33 Heat Exchanger and Burners Figure 21 15. Reconnect gas supply piping. Cleaning the Heat Exchanger and Burners 16. Turn on power and gas supply to unit. NOTE: Use papers or protective covering in front of the 17. Set thermostat and check for proper operation. furnace during cleaning.
  • Page 34 Heat Exchanger and Burner Assembly Removal * Re-install screws per the numbered sequence shown Air Fuel Plenum Heat Exchanger Gasket *Air Fuel Plenum Gas Valve Burner Gasket Gasket (replace) Debri Screen Air Intake Assembly Figure 21. Wiring and Sequence of Operation WARNING When there is a call for heat, the Comfort Sync enabled...
  • Page 35 Figure 22. 508033-02 Issue 2135 Page 35 of 48...
  • Page 36 Applications Using a Two-Stage Thermostat Applications Using A Single-Stage Thermostat A - Heating Sequence -- Integrated Control Thermostat B - Heating Sequence -- Integrated Control Thermostat Selection DIP Switch 1 OFF in “Two-Stage” Position Selection DIP Switch 1 ON in “Single-Stage” Position (Factory Setting) NOTE: In these applications, two-stage heat will be 1.
  • Page 37 Communicating Enabled Furnace and Non- Communicating Enabled Furnace and Communicating Outdoor Unit Communicating Enabled Outdoor Unit COMMUNICATING FURNACE COMMUNICATING FURNACE OPTIONAL DISCHARGE AIR SENSOR OPTIONAL DISCHARGE AIR SENSOR OPTIONAL OUTDOOR OPTIONAL COMMUNICATING AIR SENSOR OUTDOOR THERMOSTAT AIR SENSOR COMMUNICATING THERMOSTAT DOOR AIR CONDITIONING OR HEAT PUMP UNIT NON-COMMUNICATING...
  • Page 38 Optional Accessories for use with Communicating System NOTE: COMMUNICATING THERMOSTAT SENSES HUMIDITY 120V CONNECTIONS & CONTROLS HUM CONTACTS TO CYCLE HUMIDIFIER BASED ON DEMAND. NO OTHER CONTROL OR HUMIDISTAT REQUIRED. “HUM” CONTACT IS CLOSED ANYTIME HUMIDITY DEMAND IS PRESENT DOOR UNITS). COMMUNICATING ENABLED FURNACE 24V HUMIDIFIER CONNECTIONS...
  • Page 39 DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Thermostat Thermostat Wiring Connections System Options Heating Stages 1 Heat / 1 Cool FURNACE OUTDOOR T'STAT TERM. STRIP UNIT NOTE - Use DIP switch 2 to set second-stage heat ON delay.
  • Page 40 DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Thermostat Thermostat Wiring Connections System Options Heating Stages 2 Heat / 2 Cool FURNACE OUTDOOR T'STAT TERM. STRIP UNIT CUT ON-BOARD LINK W915 2 STAGE COMPR ZONING...
  • Page 41 DIP Switch Settings and On-Board Links DIP Switch 1 Wiring Connections Thermostat On Board Links Must Be Cut To Select Thermostat Heating System Options Stages Dual Fuel FURNACE HEAT PUMP T'STAT TERM. STRIP Single Stage Heat Pump CUT ON-BOARD LINK W951 67M41* HEAT...
  • Page 42 DIP Switch Settings and On-Board Links DIP Switch 1 Wiring Connections Thermostat On Board Links Must Be Cut To Select Thermostat Heating System Options Stages Dual Fuel FURNACE HEAT PUMP T'STAT TERM. STRIP Single Stage Heat Pump CUT ON-BOARD LINK W951 67M41* HEAT...
  • Page 43 Program Unit Capacity Size Modes − − Power-Up - Number displayed represents by integrated control unit size code (furnace model − and capacity). If three horizontal bars are displayed followed by continuous E203, furnace control does not recognize unit size code. Configure per the following: Furnace control in IDLE mode No heating, cooling or indoor fan operation)
  • Page 44 Troubleshooting CALL FOR FIRST-STAGE HEAT CALL FOR 1ST STAGE HEAT (LOW FIRE) INDOOR BLOWER OFF AFTER HEAT FAN OFF DELAY (LOW HEAT SPEED) INDOOR LIMIT BLOWER OFF HIGH ERROR SWITCH INDOOR WATCHGUARD − AFTER HEAT FAN LIMIT SWITCH CODE CLOSED WITHIN 3 BLOWER ERROR CODE OFF DELAY (LOW...
  • Page 45 CALL FOR SECOND-STAGE HEAT CALL FOR 2ND STAGE HEAT (HIGH FIRE) SINGLE STAGE 2 STAGE THERMOSTAT THERMOSTAT 2ND STAGE RECOGNITION DELAY ON DELAY (30 SECONDS) EXPIRED? EXPIRED? ONLY FOR 1ST REQUEST FOR 2ND STAGE HEAT INDUCER SWITCHED TO HIGH SPEED HIGH PRESSURE SWITCH INDUCER SWITCHED...
  • Page 46 CALL FOR HEAT SATISFIED FIRST-STAGE HEAT SECOND-STAGE HEAT RUN MODE: 1ST OR 2ND STAGE CALL FOR HEAT. ALL INPUTS MONITORED (LIMIT, PRESSURE, CALL FOR HEAT/COOL, FLAME LEVEL) 2ND STAGE HEAT 2ND STAGE CALL FOR HEAT SATISFIED? DE−ENERGIZE 2ND STAGE GAS VALVE INDUCER SPEED SWITCHED TO LOW SPEED INDOOR BLOWER SWITCHED...
  • Page 47 CALL FOR COOLING 1ST STAGE COOLING REQUEST RECEIVED WAIT FOR COMPRESSOR TIMED OFF DELAY TO EXPIRE ENERGIZE 1ST STAGE COOLING CONTACTOR (COMPRESSOR & FAN) INDOOR BLOWER 2 SECOND ON DELAY ENERGIZE INDOOR BLOWER (LOW COOLING MODE) MAINTAIN INDOOR BLOWER (LOW COOLING MODE) 1ST STAGE 2ND STAGE COOLING REQUEST...
  • Page 48 CALL FOR FAN CALL FOR FAN INDOOR BLOWER ON CONTINUOUS FAN SPEED CALL FOR FAN MAINTAIN INDOOR BLOWER AT REMOVED? CONTINUOUS FAN REQUEST MAINTAIN INDOOR FOR COOLING GO TO CALL FOR COOLING BLOWER AT RECEIVED? CONTINUOUS FAN REQUEST INDOOR BLOWER OFF FOR HEAT GO TO CALL FOR 1ST STAGE HEAT RECEIVED?