Brand: Allied Air Enterprises
Category: Furnace
Manual Type:
Language:
Manual for A80UH2E / 80G2UHE
Uploaded: March 30, 2025, 4:26 p.m.
Warranty Summary
Refer to the Allied Air Limited Warranty for details on coverage and duration.
This service manual outlines the operation of the A80UH2E / 80G2UHE furnace, which features a two-stage heating and constant torque ECM blower motor. The electronic ignition system initiates the heating cycle by monitoring pressure switches and energizing the combustion air inducer. The unit supports both single-stage and two-stage thermostat operation, selectable via a DIP switch. In two-stage mode, the furnace modulates between first and second stage heat based on thermostat demand, ensuring efficient and comfortable heating. Safety features include flame rollout switches and limit controls to prevent overheating and ensure safe operation.
Troubleshooting and error codes
| Code | Diagnostic Codes/Status of Equipment | Action Required to Clear and Recover |
|---|---|---|
| No change (idle)* | Idle mode (Decimal blinks at 1 Hertz -- 0.5 second ON, 0.5 second OFF). | Remain in idle mode |
| Solid "E" | Enter diagnostic recal mode | |
| Solid "F" | Enter flame signal mode | |
| C | Cooling stage (1 second ON, 0.5 second OFF) 1 or 2 displayed / Pause / Repeat codes. | |
| d | Dehumidification mode (1 second ON, 1 second OFF) / Pause / Repeat Codes). | |
| H | Gas Heat Stage (1 second ON, 0.5 second OFF) 1 or 2 displayed / Pause / Repeat codes. Blinking during ignition. | |
| h | Heat pump stage. | |
| E110 | Low line voltage. | Line Voltage Low (Voltage lower than nameplate rating). Check power line voltage and correct. Alarm clears 5 seconds after fault recovered. |
| E111 | Line voltage polarity reversed. | Reverse line power voltage wiring. System resumes normal operation 5 seconds after fault recovered. |
| E112 | Ground not detected. | System shuts down. Provide proper earth ground. System resumes normal operation 5 seconds after fault recovered. |
| E113 | High line voltage. | Line Voltage High (Voltage higher than nameplate rating). Provide power voltage within proper range. System resumes normal operation 5 seconds after fault recovered. |
| E114 | Line voltage frequency out-of-range. | No 60 Hertz Power. Check voltage and line power frequency. Correct voltage and frequency problems. System resumes normal operation 5 seconds after fault recovered. |
| E115 | Low 24V - Control will restart if the error recovers. | 24-Volt Power Low (Range is 18 to 30 volts). Check and correct voltage. Check for additional power-robbing equipment connected to system. May require installation of larger VA transformer to be installed in furnace / air handler. Clears after fault recovered. |
| E117 | Poor ground detected (Warning only) | Provide proper grounding for unit. Check for proper earth ground to the system. Warning only will clear 30 seconds after fault recovered. |
| E125 | Control failed self-check, internal error, failed hardware. Will restart if error recovers. Integrated control not communicating. Covers hardware errors (flame sense circuit faults, pin shorts, etc.). | Hardware problem on the control. Cycle power on control. Replace if problem prevents service and is persistent. Critical alert. Cleared 300 seconds after fault recovered. |
| E200 | Hard lockout - Rollout circuit open or previously open. | Correct cause of rollout trip, or replace flame rollout switch. Test furnace operation. Cleared after fault recovered. |
| E204 | Gas valve mis-wired. | Check gas valve operation and wiring. Clears when repaired. |
| E205 | Gas valve control relay contact shorted. | Check wiring on control and gas valve. If wiring is correct, replace control. |
| E206 | Gas valve second-stage relay failure. | Furnace will operate on 1st stage for remainder of the heating demand. Will clear after fault recovered. If unable to operate 2nd stage, replace control. |
| E207 | Hot surface ignitor sensed open. | Measure resistance of hot surface ignitor. Replace if open or not within specified range found in IOM. Resumes normal operation after fault is cleared. |
| 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. | Check operation of low pressure switch to see if it is stuck closed on heat call longer than 150 seconds. Measure operating pressure (inches w.c.). Inspect vent and combustion air inducer for correct operation and restriction. Resumes normal operation after fault is cleared. |
| E225 | High pressure switch failed open. | Check pressure (inches w.c.) of high 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. |
| E226 | High pressure switch failed closed. | Check operation of high 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. |
| E227 | Low pressure switch open during trial for ignition or run mode. | 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. |
| E229 | Ignition on High Fire - Information Only. | Code is displayed if 1) low pressure switch fails to close, then furnace will switch to high speed inducer to close both low and high pressure switches, then furnace lights on high fire, or 2) if continuous fan is active, furnace lights on high fire for 60 seconds to improve heat exchanger warm up time. |
| E240 | Low flame current - Run mode. | Check micro-amperes of flame sensor using control diagnostics or field-installed mode. Clean or replace sensor. Measure voltage of neutral to ground to ensure good unit ground. Alert clears after current heat call has been completed. |
| E241 | Flame sensed out of sequence - Flame still present. | Shut off gas. Check for gas valve leak. Replace, if necessary. Alert clears when fault is recovered. |
| E250 | Limit switch circuit open. | Check for proper firing rate on furnace. Ensure there is no blockage in heater. Check for proper air flow. If limit not closed within 3 minutes, unit will go into 1-hour soft lockout. Resumes normal operation after fault is cleared. |
| E270 | Soft lockout - Exceeded maximum number of retries. No flame current sensed. | Check for proper gas flow. Ensure that ignitor is lighting burner. Check flame sensor current. Clears when heat call finishes successfully. |
| E271 | Soft lockout - Exceeded maximum number of retries. Last retry failed due to the pressure switch opening. | 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. Clears when heat call finishes successfully. |
| E272 | Soft lockout - Exceeded maximum number of recycles. Last recycle due to the pressure switch opening. | Check operation of low pressure switch to see if it is stuck closed on heat call. Check pressure (inches w.c.) of high pressure switch closing on heat call. Measure operating pressure (inches w.c.). Inspect vent and combustion air inducer for correct operation and restriction. Clears when heat call finishes successfully. |
| E273 | Soft lockout - Exceeded maximum number of recycles. Last recycle due to flame failure. | Check micro-amperes of flame sensor using control diagnostics or field-installed mode. Clean or replace sensor. Measure voltage of neutral to ground to ensure good unit ground. Clears when heat call finishes successfully. |
| E274 | Soft lockout - Exceeded maximum number of recycles. Last recycle failed due to the limit circuit opening or limit remained open longer than 3 minutes. | Shut down system. 1-hour soft lockout. Check firing rate and air flow. Check for blockage. Clears when heat call finishes successfully. |
| E275 | Soft lockout - Flame sensed out of sequence. Flame signal is gone. | Shut off gas. Check for gas valve leak. 1-hour soft lockout. Clears when flame has been proven stable. |
Troubleshooting and error codes
| Code | Diagnostic Codes/Status of Equipment | Action Required to Clear and Recover |
|---|---|---|
| No change (idle)* | Idle mode (Decimal blinks at 1 Hertz -- 0.5 second ON, 0.5 second OFF). | Remain in idle mode |
| Solid "E" | Enter diagnostic recal mode | |
| Solid "F" | Enter flame signal mode | |
| C | Cooling stage (1 second ON, 0.5 second OFF) 1 or 2 displayed / Pause / Repeat codes. | |
| d | Dehumidification mode (1 second ON, 1 second OFF) / Pause / Repeat Codes). | |
| H | Gas Heat Stage (1 second ON, 0.5 second OFF) 1 or 2 displayed / Pause / Repeat codes. Blinking during ignition. | |
| h | Heat pump stage. | |
| E110 | Low line voltage. | Line Voltage Low (Voltage lower than nameplate rating). Check power line voltage and correct. Alarm clears 5 seconds after fault recovered. |
| E111 | Line voltage polarity reversed. | Reverse line power voltage wiring. System resumes normal operation 5 seconds after fault recovered. |
| E112 | Ground not detected. | System shuts down. Provide proper earth ground. System resumes normal operation 5 seconds after fault recovered. |
| E113 | High line voltage. | Line Voltage High (Voltage higher than nameplate rating). Provide power voltage within proper range. System resumes normal operation 5 seconds after fault recovered. |
| E114 | Line voltage frequency out-of-range. | No 60 Hertz Power. Check voltage and line power frequency. Correct voltage and frequency problems. System resumes normal operation 5 seconds after fault recovered. |
| E115 | Low 24V - Control will restart if the error recovers. | 24-Volt Power Low (Range is 18 to 30 volts). Check and correct voltage. Check for additional power-robbing equipment connected to system. May require installation of larger VA transformer to be installed in furnace / air handler. Clears after fault recovered. |
| E117 | Poor ground detected (Warning only) | Provide proper grounding for unit. Check for proper earth ground to the system. Warning only will clear 30 seconds after fault recovered. |
| E125 | Control failed self-check, internal error, failed hardware. Will restart if error recovers. Integrated control not communicating. Covers hardware errors (flame sense circuit faults, pin shorts, etc.). | Hardware problem on the control. Cycle power on control. Replace if problem prevents service and is persistent. Critical alert. Cleared 300 seconds after fault recovered. |
| E200 | Hard lockout - Rollout circuit open or previously open. | Correct cause of rollout trip, or replace flame rollout switch. Test furnace operation. Cleared after fault recovered. |
| E204 | Gas valve mis-wired. | Check gas valve operation and wiring. Clears when repaired. |
| E205 | Gas valve control relay contact shorted. | Check wiring on control and gas valve. If wiring is correct, replace control. |
| E206 | Gas valve second-stage relay failure. | Furnace will operate on 1st stage for remainder of the heating demand. Will clear after fault recovered. If unable to operate 2nd stage, replace control. |
| E207 | Hot surface ignitor sensed open. | Measure resistance of hot surface ignitor. Replace if open or not within specified range found in IOM. Resumes normal operation after fault is cleared. |
| 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. | Check operation of low pressure switch to see if it is stuck closed on heat call longer than 150 seconds. Measure operating pressure (inches w.c.). Inspect vent and combustion air inducer for correct operation and restriction. Resumes normal operation after fault is cleared. |
| E225 | High pressure switch failed open. | Check pressure (inches w.c.) of high 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. |
| E226 | High pressure switch failed closed. | Check operation of high 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. |
| E227 | Low pressure switch open during trial for ignition or run mode. | 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. |
| E229 | Ignition on High Fire - Information Only. | Code is displayed if 1) low pressure switch fails to close, then furnace will switch to high speed inducer to close both low and high pressure switches, then furnace lights on high fire, or 2) if continuous fan is active, furnace lights on high fire for 60 seconds to improve heat exchanger warm up time. |
| E240 | Low flame current - Run mode. | Check micro-amperes of flame sensor using control diagnostics or field-installed mode. Clean or replace sensor. Measure voltage of neutral to ground to ensure good unit ground. Alert clears after current heat call has been completed. |
| E241 | Flame sensed out of sequence - Flame still present. | Shut off gas. Check for gas valve leak. Replace, if necessary. Alert clears when fault is recovered. |
| E250 | Limit switch circuit open. | Check for proper firing rate on furnace. Ensure there is no blockage in heater. Check for proper air flow. If limit not closed within 3 minutes, unit will go into 1-hour soft lockout. Resumes normal operation after fault is cleared. |
| E270 | Soft lockout - Exceeded maximum number of retries. No flame current sensed. | Check for proper gas flow. Ensure that ignitor is lighting burner. Check flame sensor current. Clears when heat call finishes successfully. |
| E271 | Soft lockout - Exceeded maximum number of retries. Last retry failed due to the pressure switch opening. | 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. Clears when heat call finishes successfully. |
| E272 | Soft lockout - Exceeded maximum number of recycles. Last recycle due to the pressure switch opening. | Check operation of low pressure switch to see if it is stuck closed on heat call. Check pressure (inches w.c.) of high pressure switch closing on heat call. Measure operating pressure (inches w.c.). Inspect vent and combustion air inducer for correct operation and restriction. Clears when heat call finishes successfully. |
| E273 | Soft lockout - Exceeded maximum number of recycles. Last recycle due to flame failure. | Check micro-amperes of flame sensor using control diagnostics or field-installed mode. Clean or replace sensor. Measure voltage of neutral to ground to ensure good unit ground. Clears when heat call finishes successfully. |
| E274 | Soft lockout - Exceeded maximum number of recycles. Last recycle failed due to the limit circuit opening or limit remained open longer than 3 minutes. | Shut down system. 1-hour soft lockout. Check firing rate and air flow. Check for blockage. Clears when heat call finishes successfully. |
| E275 | Soft lockout - Flame sensed out of sequence. Flame signal is gone. | Shut off gas. Check for gas valve leak. 1-hour soft lockout. Clears when flame has been proven stable. |