OEM Carrier 40VA Control Circuit Transformer for Model PY3PPA048090AA

This is the OEM factory-specified control circuit transformer (part number HT01BD209) for the Carrier PY3PPA048090AA packaged unit. The transformer steps down line voltage (120V) to the 24V signal voltage that powers your thermostat, control board, and all low-voltage switching components. When it fails, nothing in the system responds — no heating, no cooling, no fan — because every control signal originates from this component. A blown fuse on the secondary side or a burned winding are the two most common failure modes.

• Specs: Input 120V AC | Output 24V AC | 40VA rating | Primary/secondary fuse-protected windings | Direct OEM replacement for part number HT01BD209
• OEM vs Generic: OEM transformers are wound and potted to Carrier's exact VA and impedance specifications. Generic substitutes can deliver unstable 24V output under load, causing intermittent lockouts, nuisance tripping, or premature control board failure.
• Install difficulty: 2/5 — Shut off all power at the disconnect and breaker before servicing. Tools needed: flathead and Phillips screwdrivers, multimeter (verify 0V before touching terminals), wire nuts or spade connectors. Always verify secondary voltage (should read 24–28V AC) after installation before closing the panel.
• Warranty: 1-year OEM factory warranty. In-stock units ship same business day when ordered before 3PM local time.

Compatibility: Designed and factory-matched for Carrier model PY3PPA048090AA packaged gas/electric units. Confirm your existing transformer's VA rating and input/output voltages against your unit's data plate before ordering. Our HVAC parts specialists are available to verify fitment — contact us before you order if unsure.