OEM Carrier Control Transformer 75VA 208/240/480V to 24VAC — Model PH3PNA042000AA

This is the factory OEM replacement control transformer (part# HT01BD242) for the Carrier PH3PNA042000AA packaged heat pump unit. The transformer steps down high-voltage supply power to the 24VAC signal used by the thermostat, control board, contactors, and all low-voltage safety circuits. When this transformer fails, the entire control circuit goes dead — the system will not respond to any thermostat call, and nothing will operate. If you're measuring 0VAC on the secondary (R and C terminals) while supply voltage is present at the primary, this transformer is the likely culprit.

• Specs: 75VA power rating | Primary input: 208/240/480V multi-tap | Secondary output: 24VAC | Frequency: 50/60Hz | Foot-mount configuration | OEM part# HT01BD242
• OEM vs Generic: This is the genuine Carrier OEM transformer, wound to exact factory VA and voltage tolerances. Undersized or off-spec aftermarket transformers can cause nuisance tripping, brown-outs on the control board, and premature contactor coil failure — especially under full multi-zone load.
• Install Difficulty: 3/5 — Requires disconnecting and safely locking out line-voltage power before access. Tools needed: multimeter, screwdrivers, wire nuts or spade connectors. Always verify primary tap wiring matches your supply voltage before energizing. Recommend confirmation by a licensed HVAC technician.
• Warranty: 1-year OEM factory warranty. In-stock units ship same business day from our warehouse when ordered by 3PM local time.

Compatibility: Designed for the Carrier PH3PNA042000AA packaged heat pump unit. This transformer is also used across a broad range of Carrier, Bryant, Payne, and ICP family equipment using the same 75VA 208/240/480V multi-tap control circuit. Always verify your existing transformer's VA rating and primary voltage tap against your unit's wiring diagram before ordering. Have questions about fitment? Our HVAC parts specialists verify compatibility before you buy — reach out before placing your order.