OEM Carrier Control Transformer 40VA 120V/24V for Model C50A402051 — Part HT01BD236

This OEM replacement control transformer (part number HT01BD236) is the factory-specified unit for the Carrier C50A402051 commercial rooftop packaged system. The transformer steps down 120V line voltage to the 24V AC signal required to power the thermostat, control board, and all low-voltage switching circuits. When this component fails, the entire control circuit goes dead — your thermostat goes blank, the system will not respond to any calls for heating or cooling, and no diagnostic codes will display because the board itself has no power.

• Specs: 40VA rating | Primary voltage: 120V AC | Secondary voltage: 24V AC | OEM part number HT01BD236 | Factory-matched impedance and thermal protection
• OEM vs Generic: This is a genuine OEM Carrier transformer wound to exact factory VA rating and insulation class. Generic substitutes frequently underperform at rated load, causing nuisance tripping of the internal thermal fuse and premature failure — especially in commercial rooftop applications with higher control circuit demands.
• Install difficulty: 2/5 — Disconnect all power at the disconnect and verify zero voltage with a multimeter before servicing. Tools needed: flathead and Phillips screwdrivers, wire nuts or spade connectors, multimeter. Note wire colors before removing the old transformer and confirm secondary output reads 24–26V AC after installation.
• Warranty: 1-year OEM factory warranty against defects. Orders placed by 3 PM local time ship same business day from our stocked warehouse.

Compatibility: Designed for the Carrier C50A402051 commercial rooftop packaged unit. Always verify your existing transformer's primary voltage, secondary voltage, and VA rating against your unit's wiring diagram before ordering. If your control circuit is blowing transformers repeatedly, inspect for shorted thermostat wiring or a grounded low-voltage circuit before replacing. Need fitment confirmation? Our HVAC parts specialists verify compatibility before you order — contact us any time.