OEM Carrier 40VA Control Transformer for Model C4850C50ZW090610 — Part HT01BD236

This is the factory OEM replacement transformer (part number HT01BD236) for the Carrier C4850C50ZW090610 packaged unit. The transformer steps down 120V line voltage to the 24V AC signal required to power your control board, thermostat circuit, and all low-voltage safety controls. When this transformer fails, the entire control circuit goes dead — your thermostat becomes unresponsive, the system won't call for heating or cooling, and no fault codes will appear because the board itself has no power. It is one of the most overlooked components during diagnostics, yet one of the most critical.

• Specs: 40VA rated | Primary: 120V | Secondary: 24V AC | OEM part number HT01BD236 | Factory-matched for Carrier C4850C50ZW090610 packaged units
• OEM vs Generic: OEM transformers are wound and tested to Carrier's exact VA rating and voltage tolerance. Undersized generic transformers can overheat, trip internal thermal fuses, and cause repeated nuisance lockouts — especially under high-demand 24V loads like zone boards or multiple damper actuators.
• Install difficulty: 2/5 — Disconnect all power before servicing. Tools needed: multimeter (verify 0V before touching terminals), flathead and Phillips screwdrivers, wire nuts or spade connectors. Always confirm primary and secondary wiring polarity matches the original unit wiring diagram located inside the cabinet door.
• Warranty: 1-year OEM factory warranty. In-stock and ships same business day from our NationalHVACParts.com warehouse.

Compatibility: Designed and factory-specified for the Carrier C4850C50ZW090610 packaged unit. Before ordering, verify your existing transformer's VA rating and primary/secondary voltages on the data plate or wiring schematic. If you're unsure of fitment, our HVAC parts specialists are available to confirm compatibility before you order — same-day shipping guaranteed on all in-stock OEM components.