OEM Carrier 40VA Control Transformer HT01BD209 for Model PY3PNA030040AA

This is the genuine OEM Carrier control transformer (part number HT01BD209) — the factory-specified replacement for the Carrier PY3PNA030040AA packaged unit. The control transformer steps down 208/240V line voltage to a stable 24V signal that powers the thermostat, contactor coils, control board, and every low-voltage component in the system. When this transformer fails, the result is total loss of 24V control power: the thermostat goes blank, the system refuses to respond to any call for heating or cooling, and no safety circuit can energize. Replacing a failed transformer is one of the fastest ways to restore a completely unresponsive unit.

• Specs: 208/240V primary | 24V secondary | 40VA power rating | 50/60 Hz | Replaces OEM part numbers HT01BD207, HT01CN232, and 9076-00
• OEM vs Generic: OEM transformers are wound to exact VA tolerance and insulation class, ensuring stable 24V output under full load. Generic substitutes can run undervoltage, causing erratic contactor chatter, nuisance lockouts, and premature control board failures.
• Install difficulty: 2/5 — Shut off all power at the disconnect and breaker before starting. Tools needed: flathead and Phillips screwdrivers, needle-nose pliers, multimeter (to verify 0V before touching terminals and 24V output after). Photograph all low-voltage wiring connections before disconnecting. Primary leads connect to line-voltage terminals; secondary leads to the 24V control circuit terminals.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Direct OEM replacement for Carrier model PY3PNA030040AA. Also fits a wide range of Carrier, Bryant, and Payne heating and cooling equipment specifying the HT01BD209 transformer. Always verify your unit's data plate voltage rating (208V or 240V) matches before installation. Our fitment team is available to confirm compatibility before you order — reach out before purchasing if you have any questions.