Equipment Guide
Heat pumps are the dominant HVAC equipment in Wake County residential construction. Understanding how they work helps homeowners evaluate service calls and make better repair-versus-replace decisions.
A heat pump moves heat rather than generating it. In summer, it extracts heat from indoor air and transfers it outside. In winter, it extracts heat from outdoor air (which contains heat down to very low temperatures) and transfers it inside. The efficiency advantage: moving heat requires less energy than generating it from resistance or combustion.
The refrigerant cycle — the mechanism that moves heat — runs in forward direction for cooling and reverse direction for heating. The reversing valve is the component that switches modes.
Capacitor failure — the most common single-component failure. Capacitors start the compressor and fan motors. A failed capacitor causes the outdoor unit to hum but not run. Relatively inexpensive repair.
Refrigerant leak — the system loses cooling and heating capacity gradually. Low refrigerant causes the compressor to work harder and can freeze the evaporator coil. Simply adding refrigerant without finding the leak is a temporary fix.
Reversing valve stuck — the valve that switches modes fails in one position. The system may cool but not heat (or vice versa). Emergency heat mode bypasses the refrigerant cycle and uses resistance strips only.
Defrost board failure — ice accumulates on the outdoor unit in cold weather and does not clear. Heating capacity drops significantly.
Compressor failure — the most expensive individual component. When it fails on a system that is 15+ years old, replacing the entire outdoor unit (or whole system) is typically the better economic choice than a compressor-only replacement.
The standard guideline is the 5000 rule: if (repair cost × age in years) exceeds $5000, replacement is likely the better option. This is a starting point, not a hard rule. Equipment condition, refrigerant type, and utility costs affect the calculation.
Reliable heating and cooling specialists present repair-versus-replace options with the estimated cost of each, not just a recommendation for the higher-ticket choice.
Wake Tech Community College offers HVAC training covering heat pump systems specifically. Cary Chamber of Commerce represents HVAC businesses operating in the Cary market.