OEM Carrier Transformer 40VA 120V/24V for Model C4850C50AK02561

This OEM step-down transformer (part# HT01BD236) is the factory-specified replacement for the Carrier C4850C50AK02561 packaged unit. The transformer converts 120V line voltage to the 24V signal voltage required to power the control board, thermostat, and all low-voltage safety controls. When it fails, the entire control circuit goes dead — your thermostat goes blank, the unit won't respond to any call for heating or cooling, and you may measure 0V at the secondary terminals with full line voltage present at the primary.

• Specs: 40VA rating | 120V primary / 24V secondary | OEM part number HT01BD236 | Factory-matched impedance and thermal protection for Carrier packaged units
• OEM vs Generic: This OEM transformer is wound to Carrier's exact VA rating and insulation class. Generic transformers are often undersized or lack the thermal cutoff protection that prevents damage to the control board during a secondary short — a very common fault condition in packaged units.
• Install difficulty: 2/5 — Shut off all power at the disconnect and breaker before servicing. Tools needed: flathead and Phillips screwdrivers, 1/4" nut driver, multimeter to verify 0V before touching terminals. Label all low-voltage wiring before disconnecting and confirm polarity on reinstall.
• Warranty: 1-year OEM factory warranty against defects. In-stock and ships same business day from our climate-controlled warehouse.

Compatibility: Designed specifically for the Carrier C4850C50AK02561 packaged unit. Verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate before ordering to confirm fitment. Our HVAC parts specialists are available to verify compatibility before you purchase — just reach out before placing your order.