Allied Air 25b93 2-stage Pressure Switch

Product Description

The ALLIED AIR 25b93 is a 2-stage pressure switch designed for use in gas furnace applications where draft inducer proving is required at two distinct pressure thresholds. The switch monitors negative pressure generated by the inducer motor and signals the control board when safe combustion airflow conditions are met. Set point high is 0.95 inches W.C. and set point low is 0.55 inches W.C. Licensed HVAC technicians typically install this component as part of routine furnace diagnostics or when replacing a failed pressure switch causing lockout faults.

This pressure switch is suited for residential and light commercial gas furnace installations that use a 2-stage inducer or 2-stage burner arrangement. Two-stage pressure switches are common in high-efficiency condensing furnaces where different firing rates require separate pressure verification before ignition is allowed to proceed. This part also carries the alternate part number 104549-20 and may be referenced by that number in service documentation.

Key Features

• 2-stage design with two independent set points for high-fire and low-fire proving
• Set point high: 0.95 inches W.C.
• Set point low: 0.55 inches W.C.
• Alternate part reference: 104549-20
• OEM-style replacement for draft inducer proving circuits

Compatibility

Designed as an OEM-style replacement pressure switch for ALLIED AIR residential gas furnace systems. Alternate part number 104549-20 may appear in OEM service documentation for cross-reference.

Installation Notes

Installation should be performed by a licensed HVAC technician in accordance with local mechanical codes and the furnace manufacturer's service documentation. Shut off power to the furnace and allow the inducer to come to a complete stop before disconnecting pressure switch hoses or wiring. Inspect rubber hose connections for cracks or blockages that could cause nuisance trips before condemning a switch. Verify set points with a manometer at startup to confirm proper inducer operation.