OEM Carrier Transformer 40VA 120V/24V for Model C50A903564

This OEM replacement transformer (part number HT01BD702) is the factory-specified step-down transformer for the Carrier C50A903564 commercial rooftop unit. The transformer converts 120V line voltage to the 24V signal required to power the control board, thermostat circuit, and all low-voltage switching components. When this transformer fails, the entire control circuit goes dark — your thermostat will appear dead, the system will not respond to any calls for heating or cooling, and you may measure 0V at the secondary terminals even with line voltage confirmed at the primary.

• Specs: 40VA rated | Primary: 120VAC | Secondary: 24VAC | Factory-matched impedance and core material for full compatibility with C50A903564 control circuit demands
• OEM vs Generic: This is the genuine OEM Carrier part (HT01BD702), wound and tested to factory specification. Generic transformers often under-deliver VA capacity under load, causing nuisance trips, brown-outs on the control board, or premature secondary-side burnout — especially in commercial rooftop applications with multiple zones or accessories drawing 24V power simultaneously.
• Install difficulty: 2/5 — Shut off all power to the unit before beginning. Tools needed: flathead and Phillips screwdrivers, wire nuts or terminal connectors, multimeter to verify 24VAC output post-install. Label and photograph all wiring connections before disconnecting the old transformer.
• Warranty: 1-year OEM factory warranty against defects in materials and workmanship. In-stock units ship same business day from our climate-controlled warehouse.

Compatibility: Engineered as a direct OEM replacement for the Carrier C50A903564 commercial rooftop packaged unit. Confirm your existing transformer's primary voltage (120V), secondary voltage (24V), and VA rating from your unit's wiring diagram or data plate before ordering. If you have any questions about fitment, our HVAC parts specialists verify compatibility before you buy — no guesswork.