System Sensor D4120W Detector Freon The Allanson 421-664 ignition transformer

The Allanson 421-664 ignition transformer is a critical replacement component engineered specifically for Webster Engineering burners

Direct Compatibility: Designed for an exact fit in York furnace parts assemblies

you would typically look for the NC/S versions or a 4-wire variant

Universal Compatibility: Fully identical to the 40003916-521/U model

s 3-prong cord directly into the back of the thermostat

System Sensor D4120W Detector Freon The Allanson 421-664 ignition transformerThe System Sensor D4120W is a high performance 4 wire photoelectric duct smoke detector specifically engineered for harsh environments and outdoor rooftop HVAC installations. This air duct smoke detector features a NEMA 4 watertight enclosure, providing superior protection against windblown dust, rain, and splashing water. Utilizing integrated low flow technology, the unit operates efficiently in airflow speeds ranging from 100 to 4,000 feet per