OEM Carrier 40VA Control Transformer HT01BD236 for Model C4850C50AK02761

This OEM control transformer (part# HT01BD236) is the factory-specified replacement for the Carrier C4850C50AK02761 packaged unit. The transformer steps down line voltage from 120V to the 24V AC signal required by your thermostat, control board, contactor coil, and all low-voltage control circuit components. When it fails, the entire control circuit goes dark — the thermostat shows no power, the system won't respond to calls for heating or cooling, and no fault codes are produced because the board itself has no power to operate.

• Specs: 40VA rating | Primary: 120V | Secondary: 24V AC | OEM part number HT01BD236 | Factory-matched impedance and thermal cutout protection
• OEM vs Generic: This OEM transformer meets Carrier's exact VA rating and thermal overload specifications. Undersized or off-tolerance generic transformers can overheat under full control circuit load, causing nuisance tripping or premature failure — especially in packaged units where multiple accessories draw from a single transformer.
• Install difficulty: 2/5 — Always shut off power at the disconnect and breaker before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or terminal connectors. Label or photograph all wiring connections before removing the old transformer. Verify 24V output with a multimeter after installation before restoring full power.
• Warranty: 1-year OEM factory warranty against defects. Ships same business day from our NationalHVACParts.com warehouse.

Compatibility: Engineered specifically for the Carrier C4850C50AK02761 packaged unit. Confirm your unit's data plate shows a 120V primary / 24V secondary control circuit before ordering. If you are unsure of fitment or have a multi-speed accessory load on your transformer circuit, our parts team is available to verify compatibility before you purchase. Order today and receive same-day shipping on all in-stock components.