OEM Carrier 40VA Control Transformer HT01BD702 for Model C50A902064

This OEM step-down transformer (part number HT01BD702) is the factory-specified replacement for the Carrier C50A902064 commercial packaged unit. The transformer converts 120V primary line voltage to the 24V secondary signal voltage that powers your thermostat, control board, contactor coils, and all low-voltage safety circuits. When the transformer fails, the entire control circuit goes dark — nothing works. Symptoms include a completely unresponsive thermostat, a system that won't heat or cool, or a tripped secondary fuse caused by a shorted control wire.

• Specs: 40VA rating | 120V primary / 24V secondary | Ring terminal or quick-connect leads | Factory-matched impedance and thermal overload protection
• OEM vs Generic: This is a genuine Carrier OEM transformer built to exact VA rating and winding specifications. Generic replacements often run under-rated VA capacity, causing the transformer to overheat and fail prematurely under normal control-circuit loads.
• Install difficulty: 2/5 — Disconnect power at the disconnect and breaker before beginning. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or terminal connectors. Verify 24V output after installation before restoring the thermostat connection.
• Warranty: 1-year OEM factory warranty against defects. In-stock and ships same business day from our NationalHVACParts.com warehouse.

Compatibility: Designed for the Carrier C50A902064 commercial rooftop/packaged unit. Always verify your existing transformer's VA rating and primary/secondary voltages on the unit data plate or wiring diagram before ordering. Our fitment team is available to confirm compatibility before you buy — same-day shipping on all in-stock OEM parts.