OEM Carrier 40VA Control Transformer for Model C50A405051

This OEM replacement transformer (part# HT01BD236) is the factory-specified 40VA step-down transformer for the Carrier C50A405051 commercial rooftop unit. The transformer converts 120V primary power to the 24V AC signal that powers the entire control circuit — including the thermostat, contactor coils, gas valve, and control board. When this component fails, the system goes completely unresponsive: the thermostat goes blank, the unit won't call for heating or cooling, and no safety or operating sequence can initiate. It's often the first component to diagnose when nothing works.

• Specs: 40VA rated | 120V primary / 24V secondary | Class 2 control transformer | Factory-matched impedance for stable control voltage under load
• OEM vs Generic: This OEM unit (HT01BD236) meets Carrier's exact VA rating and insulation class. Generic transformers frequently deliver unstable secondary voltage under load, causing intermittent lockouts, nuisance tripping of fuses, and premature control board failure.
• Install difficulty: 2/5 — Disconnect all power before servicing. Tools needed: flathead and Phillips screwdrivers, multimeter, wire nuts or spade connectors. Verify fuse condition on the 24V secondary side before installing — a shorted control component will immediately blow the new transformer. Label all wiring before disconnecting.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed for the Carrier C50A405051 commercial packaged rooftop unit. Always verify primary voltage (120V) and VA rating on your unit's wiring diagram or data plate before ordering. If your system uses a 208/240V primary, do not use this transformer. Our team is available to verify fitment before you order — same-day shipping available on all in-stock OEM parts.