How Does a Residential Heat Pump System Work?

A residential heat pump system looks and operates much like a residential air conditioning system with one notable exception—it provides both cooling and heating. Ideally suited to milder climates, a residential heat pump system uses a process called heat transfer to move heat into the home for heating and out of the home for cooling. In colder climates with more extreme seasonal temperature differences, an auxiliary heat source (either electric or gas) provides heating when outdoor temperatures (usually between 26 to 30 degrees Fahrenheit) become too cold for effective indoor heating.

Types

Heat pumps can absorb heat from the air, ground or water. Air source heat pumps dominate the residential market. Air source heat pumps are in three common designs: split system, packaged and ductless. Split system heat pumps include an indoor unit (mostly an air handler, indoor coil and controls) and an outdoor unit (outdoor coil, fan and controls). Packaged heat pumps combine the indoor and outdoor units into one that sits outside. Ductless units blow heated or cooled air directly into the room, usually from a wall or ceiling-mounted location.

How it Heats

Regardless of type, the basic heating function remains the same. Liquid refrigerant traveling through the system’s outdoor coil absorbs heat from outside air. This takes place because the temperature of the liquid refrigerant is lower than the outside air temperature even during many winter days. The compressor then pumps additional energy into the heated refrigerant in the form of temperature and pressure. The resulting super-heated vapor flows through the system’s indoor coil. Air blowing across the indoor coil absorbs the heat and travels through ducts to deliver warm air to the rooms of your home.

How it Cools

To cool your home, the heat pump system reverses the process. A residential heat pump system also provides some relief from indoor humidity by drawing moisture from the indoor air as a natural product of the cooling process.

Energy Efficiency

In most cases, residential heat pump systems operate on electricity only. To compare energy consumption between different heat pump systems, check for the HSPF (Heating Seasonal Performance Factor) rating. HSPF provides a standardized number similar to miles per gallon for cars. A higher HSPF number means higher energy efficiency and lower operating costs.

Considerations

Because a heat pump does not generate heat by burning fuel (like a gas furnace), heated air does not feel as intensely warm. However, depending on the available utilities in your area, a heat pump may be the best and most energy-efficient option. Heat pumps typically run longer heating cycles leading to more consistent indoor temperatures, preferred by some consumers.

References

• Tim Perry, Sales Manager; HVAC distributor; Indianapolis, IN
• HowStuffWorks