Charging a Residential Heat Pump

Charging the heat pump — in other words, adding more refrigerant — can be a critical step for keeping your heat pump functioning at peak capacity. A heat pump only works by transferring heat from one place to another, and that can't happen when refrigerant is low. You can manage some aspects of heat pump maintenance on your own, but a heat pump refrigerant charge isn't one of them.

Refrigerant is a critical element of your heat pump system. In heat mode, air is pulled in from outdoors and passed through metal coils. The heat from the air is absorbed by refrigerant that circulates through the system. The refrigerant then transfers that heat into the air that's forced up through your ducts and into your rooms.

The process is reversed when you use your heat pump in cooling mode. Warm air is pulled from inside your home. Refrigerant transfers that heat energy into the outdoor air while the cooled air is circulated back into your home.

Insufficient refrigerant prevents either process from working the way it should. Once a leak happens somewhere in the system, a heat pump refrigerant refill is the only way to restore your heat pump to full efficiency. Think of a heart trying to beat as someone loses a lot of blood. It may continue to pump weakly at first but will eventually stop when the pressure gets too low. A heat pump refrigerant charge is kind of like a blood transfusion for your weakened pump.

Unfortunately for budget-conscious homeowners, a heat pump refrigerant refill isn't a project you can DIY. Only certified professionals can work with refrigerant per the Environmental Protection Agency, so this job needs to be handled by an experienced HVAC technician. You'll want a pro's help anyway because the charging process isn't as simple as just filling a heat pump with Freon. (In fact, when a tech does come to charge your heat pump, Freon may not be used at all; heat pumps often use a safer alternative refrigerant these days.)

The charging process requires precise calibration, and how the technician approaches it depends on the temperature outdoors. The technician needs to troubleshoot your heat pump problems to identify the source of the original leak and fix it before refilling the system with refrigerant and making sure the refrigerant is properly pressurized.

How do you know when it's time for a heat pump refrigerant refill? There are a few telltale signs that there's something wrong with your system's refrigerant levels. Frost buildup on the pump's exterior coils is one of the most common indicators. Frost sometimes builds up on a well-functioning heat pump in cold weather, but if the unit doesn't defrost as the weather warms up or is completely encased in ice, call your HVAC company.

Pooled liquid or a gurgling sound coming from your heat pump is another potential sign of a leak. Also, because your system has to work harder when it doesn't have enough refrigerant, you may notice your electric bill rise unexpectedly when you're in need of a charge.