OEM Carrier Control Transformer 40VA 208/240V to 24V — Model PY3PNA030040AB

This OEM control transformer (part# HT01BD209) is the factory-specified replacement for the Carrier PY3PNA030040AB packaged HVAC unit. The transformer steps down high-voltage line power (208/240V) to the safe 24V AC used by your thermostat, control board, and all low-voltage system components. When the transformer fails, the entire control circuit goes dark — the thermostat loses power, the system refuses to respond to any command, and you may detect faint buzzing or burning near the control compartment. Replacing this part is the first diagnostic step when no 24V is present at the secondary terminals.

• Specs: 40VA rating | 208/240V primary | 24V AC secondary | 50/60Hz | Class 2 control transformer | Replaces HT01BD207, HT01CN232, and 9076-00
• OEM vs Generic: This is a genuine Carrier OEM transformer wound to exact factory VA and voltage tolerances. Generic aftermarket transformers are often rated at looser tolerances, risking nuisance tripping, control board damage from voltage sag, or premature winding failure under load.
• Install difficulty: 2/5 — Always de-energize the unit at the disconnect and breaker before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter (to verify 0V before and 24V after). Label all low-voltage wires before disconnecting. Confirm secondary output voltage after install before restoring the load.
• Warranty: 1-year OEM manufacturer warranty against defects. Ships same business day from our stocked warehouse.

Compatibility: Designed for the Carrier PY3PNA030040AB packaged unit. Always verify your unit's control voltage requirement (24V) and transformer VA demand against connected accessories before ordering — adding zone boards or humidifiers can exceed a 40VA transformer's capacity. Questions about fitment? Our HVAC parts specialists confirm compatibility before you order — no guesswork.