The Pentair Thermostatic Expansion Valve (473999Z) is the OEM replacement expansion valve for the Pentair UltraTemp Heat Pump Series, specifically the 120HC and 110 models.
⚠️ IMPORTANT: HEAT PUMP REFRIGERANT COMPONENT — PROFESSIONAL SERVICE REQUIRED
Gas and electrical heater components must be serviced by a licensed pool professional or qualified HVAC technician. Do not attempt to service gas or high-voltage components without proper certification. Thermostatic expansion valves are refrigerant-circuit components — handling refrigerants requires EPA Section 608 certification.
The thermostatic expansion valve (TXV) regulates refrigerant flow into the evaporator coil, metering the precise volume required to maintain efficient heat transfer across the refrigerant cycle. A failed or out-of-calibration TXV causes the heat pump to lose heating capacity, short-cycle, or fail to reach target water temperature. Replacing with the correct OEM valve restores the refrigerant circuit to factory specification.
Specifications
| Pentair Part Number |
473999Z |
| Part Name |
Thermostatic Expansion Valve |
| Quantity Included |
Each |
Fits Into
| Brand |
Equipment Line |
Model / Part Number |
Notes |
| Pentair |
UltraTemp Heat Pump — UltraTemp Series |
120HC |
Model 120HC, 110 |
| Pentair |
UltraTemp Heat Pump — UltraTemp Series |
110 |
Model 120HC, 110 |
Compatibility is based on Pentair parts documentation and available OEM records. This is not an exhaustive list. For certainty, verify the part number in your equipment's manual or on the original part itself before ordering.
Pro Tip
Before ordering, confirm the part number stamped or labeled on your existing expansion valve matches 473999Z. TXV capacity and pressure ratings are matched to the specific refrigerant circuit design of each heat pump model — substituting an incorrectly rated valve will result in poor heating performance or compressor damage. This replacement must be installed by a certified HVAC or refrigeration technician with EPA Section 608 certification, as the refrigerant circuit must be recovered, evacuated, and recharged during the repair.
