One system that both cools and heats. In summer it moves heat from inside the building to outside, exactly like an air conditioner. In winter it reverses the refrigerant cycle and moves heat from outdoor air to inside. That reversal is handled by a component called the reversing valve, which is unique to heat pumps.

Because it never gets an off season. A heat pump in East Central Florida cools through long summers and heats during cold fronts, so its compressor, electrical components, and refrigerant circuit accumulate close to year-round runtime. More operating hours in the same number of calendar years means more accumulated wear.

Usually one, and usually the reversing valve or the auxiliary heat side. Because the refrigerant cycle runs in opposite directions depending on mode, a fault can be completely invisible in cooling and obvious in heating. This is why we verify operation in both modes rather than only the one that prompted the call.

They are temperature measurements taken alongside refrigerant pressures that reveal whether the charge is genuinely correct and the system is transferring heat properly. Pressure alone can look acceptable on a system that is performing poorly, so verifying superheat and subcool is what separates a real diagnosis from a gauge reading.

Some frost during heating operation is normal, and the defrost board is supposed to clear it automatically on a cycle. Persistent ice means the defrost board, sensor, or reversing valve is not doing its job, or that airflow and charge problems are involved. Running the system through it risks the compressor.

Twice a year, more than any other equipment in the building. A spring visit checks the cooling side before summer load, a fall visit checks heating mode, heat strips under load, the reversing valve, and the defrost board before the first cold front. Each visit inspects things the other cannot.