Your Air-Source Heat Pump and Its 3 Cycles
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Your Air-Source Heat Pump and Its 3 Cycles


Heat pumps are marvelous home-comfort systems that, at the touch of a button, the flip of a switch or with programmable thermostat settings, shift between heating, cooling and defrost cycles. This ensures that your comfort and energy bills groove with outside temperatures no matter the daily or seasonal weather changes. Learn the basics of heat pump cycles to maximize system performance, comfort, and energy savings all year long.

Heat Pump Cycles

Heat pumps are engineered to harness the natural movement of heat energy from a warmer space to a cooler space by the principles of refrigeration – manipulating refrigerant under pressure changes. The basics of heat pump cycles for either cooling or heating are as follows:

In cooling mode, an air-source heat pump operates very much like a split-system air conditioner:

  • The compressor compresses or “pumps” refrigerant through the system.
  • As a result of changes in pressure, the refrigerant makes the inside evaporator coil get very cold, while the condenser coil becomes very hot.
  • The blower motor fan or air handler blows air across the hot evaporator coils, cooling it about 15-20 degrees. The chilled air is then circulated through your home via ductwork.
  • Meanwhile, the hot refrigerant is pumped back outside to the condensing unit where a fan blows air across the condenser coils. This extracts heat from the coils, which is then exhausted into the outside air. At this point, the refrigerant can run its cycle again, and through pressure changes, cool the evaporator coil.
  • With a heat pump in heating mode, the reversing valve switches the flow of refrigerant between the condenser and evaporator coils. Heat is pulled from the outside air and then brought inside, via refrigerant, where it’s transferred to your indoor air and circulated through your ducts.

Defrost Cycle

In defrost mode, the reversing valve changes the direction of refrigerant so that the outside coil becomes hot. When ice accumulation has melted from the coil, the heat pump returns to normal heating cycle.

For more information about heat pump cycles or any HVAC questions and issues you may have for your Portland area home, please contact our professionals at Roth Heating & Cooling today!

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