OEM Carrier Control Transformer 40VA 208/240V to 24V for Model PY4GNAA48115AA

The Carrier HT01BD209 is the factory-original control transformer for the Carrier PY4GNAA48115AA packaged unit. This transformer steps line voltage (208/240V primary) down to a safe 24V secondary to power the entire low-voltage control circuit — including the thermostat, contactor coil, control board, and safety switches. When this transformer fails, nothing in the system responds: the thermostat goes blank, the unit won't start, and there is no 24V present at the control board. A blown transformer is often caused by a shorted wire, a failed component elsewhere in the circuit, or simple end-of-life wear — always inspect for downstream shorts before installing a replacement.

• Specs: 40VA capacity | 208/240V primary input | 24V secondary output | 50/60Hz rated | Replaces OEM part numbers HT01BD207, HT01CN232, and 9076-00
• OEM vs Generic: This is the genuine Carrier OEM part — factory-wound to exact VA and voltage tolerances. Aftermarket transformers frequently run undersized VA ratings, causing nuisance overloads and premature failure under normal system demand.
• Install difficulty: 2/5 — Shut off all power at the disconnect and breaker before starting. Tools needed: flathead and Phillips screwdrivers, multimeter (to verify 0V before touching wires and to confirm 24V output after install), wire nuts or terminal connectors. Label all wiring before disconnecting. Always check for shorted wires before powering up the new transformer.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed as the direct OEM replacement for Carrier model PY4GNAA48115AA packaged units. Also cross-references Bryant and Payne systems sharing the HT01BD209 / HT01CN232 specification. Verify your unit's data plate voltage requirements before ordering. Have questions about fitment? Our HVAC parts specialists confirm compatibility before you buy — reach out today.