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This OEM control circuit transformer (part number HT01CN241) is the factory-specified replacement for the Carrier FB4BNF030015AAAA fan coil air handler. The transformer steps down line voltage from 120V to 24V AC to power the low-voltage control circuit — including the thermostat, control board, and all relay coils. When this transformer fails, the entire control system goes dark: the thermostat loses power, the system refuses to respond to any call for heating or cooling, and nothing turns on. If your system is completely unresponsive and your low-voltage fuse keeps blowing, a failed transformer is the most likely culprit.
Compatibility: Designed specifically for the Carrier FB4BNF030015AAAA fan coil air handler. Verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering. Our team is available to confirm fitment — order with confidence.