OEM Carrier 40VA Control Transformer for Model C4850C50ZN040500

This OEM Carrier transformer (part# HT01BD236) is the factory-specified replacement for the C4850C50ZN040500 packaged unit. The transformer steps down 120V line voltage to 24V AC to power the entire control circuit — including the thermostat, contactor coil, and control board. When it fails, the result is total system silence: no thermostat response, no fan, no heat or cooling. A blown transformer is often the first sign of a shorted control component downstream.

• Specs: 40VA rating | Primary: 120V AC | Secondary: 24V AC | Factory-matched OEM replacement | Part# HT01BD236
• OEM vs Generic: OEM transformers are wound to exact VA and voltage tolerances for the C4850C50ZN040500's control board demands. Generic units frequently underperform on VA capacity, causing nuisance trips, overheating, or repeat failures if a downstream short exists.
• Install difficulty: 2/5 — Disconnect power at the breaker before beginning. Tools needed: flathead and Phillips screwdriver, multimeter (to verify 24V output and check for downstream shorts before energizing). Always check low-voltage wiring for shorts before installing a new transformer.
• Warranty: 1-year OEM factory warranty. In stock and ships same business day from our warehouse.

Compatibility: Designed for Carrier model C4850C50ZN040500 packaged unit. Verify primary voltage (120V) and VA rating on your unit's data plate before ordering. If you're replacing a failed transformer, always diagnose the 24V circuit for a short-to-ground before powering up — otherwise the new transformer will fail immediately. Our HVAC parts team is available to confirm fitment before you order.