HOW DOES A HEAT PUMP WORK?
According to the Department of Energy, air source heat pumps (ASHPs) are the most common heat pump. With this type of heat pump, the heat is transferred between your home and the outdoor air. As you’ll see in this guide, there are many configurations of air source heat pumps, so be sure to talk to your contractor to determine which one will work best for your home. Unlike a gas furnace or wood burning stove, heat pumps don’t create heat; instead, they move heat from one place to another. This is possible because heat energy is naturally present in the earth and air, even when it is cold outside. Essentially, a heat pump functions as an air conditioner that can also work in reverse. In the summer, as shown in Figure 1, the equipment moves heat from inside to outside the home; and in the winter, as shown in Figure 2, heat is extracted from the air outside and moved inside the home. This is also the same technology that your refrigerator uses to keep your food cold.
FIGURE 1: HEAT PUMP – COOLING MODE
FIGURE 2: HEAT PUMP – HEATING MODE
A heat pump will consistently maintain the desired temperature throughout your home by providing a constant stream of air at a low volume for long periods of time. You may not hear the unit operate or feel blasts of hot air in the winter, but as long as your thermostat shows the desired temperature you can be sure it’s working! Not Your Grandpa’s Heat Pump. Tremendous improvements in technology in the past 30+ years—such as variable speed drive motors (also called inverter-driven compressors)—have rendered a new generation of air source heat pumps that can deliver heat more efficiently and reliably at much lower temperatures. The compressor is the “engine” of the heat pump, and with the ability to vary speed, it offers benefits much like a multi-speed bicycle compared to a single-speed bicycle. In contrast to single- and two-stage compressors, variable speed compressors can run at higher speeds when it’s cold outside and can run at lower speeds during the summer and during days with moderately cold temperatures.
SINGLE-STAGE: Heat pump that has limited flexibility since it only runs at 100% capacity.
TWO-STAGE: Heat pump that has two distinct stages of heating and cooling; typically high capacity of 100% and low capacity around 70%.
VARIABLE SPEED: Heat pump that uses an inverter motor to allow for a full range of operation.
This operates like a car’s accelerator in that the heat pump finds the right speed to run most efficiently.
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ELECTRIC HEAT PUMP CUSTOMER BUYING AND OPERATION GUIDE FOR SINGLE-FAMILY HOMES
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