Yes, professional HVAC technicians routinely charge or add refrigerant to a residential heat pump while the system is operating in cooling mode, as this is the standard industry procedure for measuring superheat and subcooling parameters accurately. When a heat pump runs in cooling mode, the outdoor condensing unit functions as the condenser and the indoor coil functions as the evaporator, allowing technicians to attach manifold gauges to the service ports and calculate precise charge levels using outdoor ambient temperatures. However, charging a system in cooling mode requires specialized technical training, EPA certification, and precise measurement tools to prevent overcharging, which can slug and destroy the compressor. Homeowners should never attempt DIY refrigerant charging. You can verify successful charging when correct subcooling and superheat values are achieved.
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