OEM Carrier Control Transformer 40VA 208/240V to 24V for Model PH4ZNA042000AA

This OEM control transformer is the factory-specified replacement for the Carrier PH4ZNA042000AA packaged HVAC unit. The transformer steps down 208/240V line voltage to the 24V signal voltage that powers your thermostat, control board, contactors, and every other low-voltage component in the system. When this part fails, the entire control circuit goes dead — the unit will not respond to thermostat calls, and nothing will turn on. A failed transformer is one of the most common causes of a completely unresponsive HVAC system.

• Specs: 40VA capacity | 208/240V primary input | 24V secondary output | 50/60 Hz rated | OEM part number HT01BD209 | Also replaces HT01BD207, HT01CN232, and 9076-00
• OEM vs Generic: OEM transformers are wound and rated to exact factory tolerances, ensuring stable 24V output under all load conditions. Generic units may exhibit voltage sag under full load, causing erratic thermostat behavior or nuisance control board faults.
• Install difficulty: 2/5 — Disconnect all power before starting. Tools needed: flathead and Phillips screwdrivers, wire stripper, multimeter. Photograph all wiring connections before removal. Verify 24V output at secondary terminals after installation before closing the cabinet.
• Warranty: 1-year OEM factory warranty. Ships same business day from our warehouse.

Compatibility: Fits Carrier model PH4ZNA042000AA packaged unit. Also compatible with select Bryant and Payne units using the same 40VA 208/240V–24V transformer specification. Always verify your unit's data plate and existing transformer VA and voltage ratings before ordering. Questions about fitment? Our HVAC parts specialists confirm compatibility before you buy.