The answer to 'why is my heat pump short cycling' is that there are several common causes, including a problem with the thermostat, issues with the compressor or refrigerant levels, or a malfunctioning defrost cycle. Short cycling, where the heat pump turns on and off frequently, can be caused by the system trying to compensate for these underlying issues.
Some common symptoms of short cycling include the heat pump not reaching the desired temperature, frequent on/off cycling, and higher energy bills. Solutions may involve adjusting the thermostat settings, checking refrigerant levels, cleaning the coils, or addressing other mechanical problems. If the issue persists, it's best to call in a professional HVAC technician to diagnose and repair the problem.