OEM Carrier Control Transformer 40VA 208/240V to 24V for Model PH3ZNB042000AB

This OEM control transformer is the factory-specified replacement for the Carrier PH3ZNB042000AB packaged HVAC unit. Its sole job is to step down the 208/240V line voltage to the 24V signal that powers your thermostat, control board, gas valve, and every other low-voltage component in the system. When the transformer fails — due to a short, overload, or age — the entire control circuit goes dead: the thermostat goes blank, the unit won't respond to any call for heating or cooling, and you'll typically measure 0V at the 24V secondary terminals.

• Specs: 40VA capacity | 208/240V primary input | 24V secondary output | 50/60 Hz | OEM part number HT01BD209 | Replaces HT01BD207, HT01CN232, 9076-00
• OEM vs Generic: OEM transformers are wound and encapsulated to Carrier's exact VA and voltage tolerances. Undersized or off-tolerance generic units can cause nuisance lockouts, erratic thermostat behavior, or premature secondary component failures.
• Install difficulty: 2/5 — Shut off power at the disconnect and verify zero voltage with a multimeter before touching any wiring. Tools needed: flathead and Phillips screwdrivers, multimeter, wire stripper. Label all wires before disconnecting — the primary (line) and secondary (low-voltage) sides must not be swapped.
• Warranty: 1-year OEM factory warranty against defects. Ships same business day from our stocked warehouse.

Compatibility: Engineered for the Carrier PH3ZNB042000AB packaged unit. Always verify your existing transformer's VA rating and primary voltage on the unit data plate before ordering to ensure a correct fit. Have a question? Our HVAC parts team confirms fitment before you buy — order with confidence and get it back up and running today.