F125AA1AC1AD1AG2AH3AK1 UNIT EQUIPPED FOR NATURAL GASALUMINIZED STEEL HEAT EXCHANGERALUMINIZED STEEL BURNERTWO-STAGE VALVE (RECIRCULATED HEATING ONLY - THERMOSTAT CONTROLLED)SPARK-IGNITED, INTERMITTENT SAFETY PILOT WITH ELECTRONIC FLAME SUPERVISION AND TIMED LOCKOUT (REQUIR 115/1/60 SUPPLY VOLTAGEREZNOR