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This OEM Carrier transformer (part #HT01BD242) is the factory-specified replacement for the Carrier PH3GNAA36000AA packaged unit. The transformer steps down high-voltage line power — 208V, 240V, or 480V primary — to the 24VAC secondary voltage that powers your entire low-voltage control circuit: thermostat, contactor coil, control board, and safety switches. When this transformer fails, the result is a completely unresponsive system — no thermostat response, no contactor pull-in, nothing. A failed transformer is often misdiagnosed as a control board fault, making it one of the first components to verify during a no-power diagnostic.
Compatibility: Direct OEM replacement for Carrier PH3GNAA36000AA packaged unit. Verify your unit's supply voltage (208/240V or 480V) matches the correct primary tap before installation. Compatible across Carrier air conditioners, furnaces, heat pumps, and packaged RTU applications using the HT01BD242 specification. Questions about fitment? Our HVAC parts specialists confirm compatibility before you order — no guesswork.