OEM Carrier Control Transformer 120V–24V 40VA for Model PY3PNA024040NA

This OEM Carrier control transformer (part number HT01BD209) is the factory-specified replacement for the Carrier PY3PNA024040NA packaged unit. The transformer steps down line voltage (120V primary) to the 24V AC signal that powers your thermostat, control board, and all low-voltage switching circuits. When this part fails, the entire control circuit goes dead — the thermostat loses power, the system stops responding to calls for heating or cooling, and no fault codes are generated because the board itself has no power to report them.

• Specs: 120V primary | 24V secondary output | 40VA rated | Factory-matched OEM tolerance | Spade or screw terminal connections
• OEM vs Generic: OEM transformers are wound and rated to exact factory VA specifications, ensuring the 24V rail stays stable under full control-circuit load. Generic units can sag under load, causing intermittent lockouts, nuisance tripping of the secondary fuse, and premature control board failure.
• Install difficulty: 2/5 — Disconnect all power before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter (to verify 24V output after install), wire nuts or spade connectors. Photograph all wiring before disconnecting the old transformer.
• Warranty: 1-year OEM factory warranty. In-stock and ships same business day from our warehouse.

Compatibility: Engineered as a direct OEM fit for Carrier model PY3PNA024040NA. Always verify primary voltage and VA rating on your unit's data plate before ordering. If you are unsure of fitment, our HVAC parts specialists can confirm compatibility before you purchase — same-day shipping available on all in-stock orders.