OEM Carrier 75VA Control Transformer HT01BD242 for Model PH3ZNA030000AA

This is the factory OEM replacement control transformer for the Carrier PH3ZNA030000AA packaged unit. The transformer steps down the high-voltage primary supply (208/240/480V) to the 24VAC secondary signal that powers the entire control circuit — including the thermostat, contactor coil, gas valve, and all safety switches. When this transformer fails, nothing in the system responds: the thermostat goes blank, the unit won't stage heating or cooling, and there are no error codes because the control board itself has lost power. A failed transformer is often misdiagnosed as a board failure, so always verify 24V output at the secondary terminals before replacing more expensive components.

• Specs: Primary 208/240/480VAC | Secondary 24VAC | 75VA rated | 50/60Hz | Foot-mount configuration | OEM part number HT01BD242
• OEM vs Generic: This is a genuine Carrier OEM transformer wound to exact factory VA and voltage tolerances. Undersized or off-tolerance aftermarket transformers can sag under load, causing intermittent lockouts and nuisance tripping of low-voltage fuses — especially in multi-stage systems with higher control circuit draw.
• Install difficulty: 3/5 — Disconnect all power before servicing. Tools needed: multimeter (verify 0V at primary before touching wiring), wire strippers, screwdriver, and needle-nose pliers. Label all low-voltage wires before disconnecting. Check for a blown 3A inline fuse on the secondary — a shorted wire is often what burned the original transformer.
• Warranty: 1-year OEM factory warranty. In-stock orders ship same business day from our warehouse.

Compatibility: Designed for the Carrier PH3ZNA030000AA packaged unit. Also cross-references to Bryant, Payne, ICP, Heil, Tempstar, and Comfortmaker units sharing the HT01BD242 specification. Verify your unit's primary voltage (208/240V or 480V) on the data plate before ordering — voltage must match. Questions about fitment? Our HVAC parts specialists verify compatibility before you order.