What causes fault code GEN-AIR1 (HVAC Supply Air Temperature Alarm)?

Chiller or boiler serving AHU is down. Cooling or heating coil valve actuator failed — stuck open or closed. Mixed air dampers not modulating — stuck in one position. Temperature sensor in duct drifted or failed. Filter clogged — restricting airflow and affecting temperature

How do I fix fault code GEN-AIR1?

Check AHU (Air Handling Unit) status — operating normally?. Verify chiller/boiler is running and supplying correct temperature medium. Check coil valve position — should modulate with demand. Test temperature sensor — compare to portable probe reading. Replace air filters if differential pressure indicates clogged. Check damper positions and actuator operation

HVAC Supply Air Temperature Alarm

GEN-AIR1

Plant HVAC system supply air temperature outside acceptable range for production area.

low general

hvac temperature air handling cooling heating

Probable Causes (ranked)

Chiller or boiler serving AHU is down
Cooling or heating coil valve actuator failed — stuck open or closed
Mixed air dampers not modulating — stuck in one position
Temperature sensor in duct drifted or failed
Filter clogged — restricting airflow and affecting temperature

Fix Steps

1 Check AHU (Air Handling Unit) status — operating normally?
2 Verify chiller/boiler is running and supplying correct temperature medium
3 Check coil valve position — should modulate with demand
4 Test temperature sensor — compare to portable probe reading
5 Replace air filters if differential pressure indicates clogged
6 Check damper positions and actuator operation

Field Trick

If the supply air temp is wrong but everything 'looks' fine, check the mixing dampers. A stuck return air damper or outside air damper completely changes the supply temp.

Suggested Replacement Parts

Parts matched to fault category: Solenoid Valve

SMC SY3120 Solenoid Valve P/N: SY3120-5LZD-M5 5/2 way, 24VDC, M5 ports, direct piping, 0.15-0.7 MPa

AutomationDirect $32.00 Amazon $28.00 McMaster-Carr $45.00 Grainger $42.00

Festo VUVG Solenoid Valve P/N: VUVG-LK14-M52-AT-G18-1R8L 5/2 way, 24VDC, G1/8 ports, spring return

AutomationDirect $55.00 Amazon $62.00 Grainger $70.00

Air Pressure Regulator + Filter Combo P/N: AW30-03BG SMC AW series, 3/8 NPT, 5-125 PSI, with gauge and bowl guard

AutomationDirect $38.00 Amazon $32.00 McMaster-Carr $48.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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