Ground & Air Source Heat Pump Heating Systems

There are two basic types of heat pumps and both grown in popularity, regardless of where you live in the US.  Technological advances are making air source heat pumps one of the most efficient heating systems, so more homeowners are choosing them every year, even matching them to a gas or oil furnace as a high efficiency heat source in your home.

Ground source heat pumps are even more efficient and with the cost of them coming down in recent years, they are now a viable option for many more consumers.  Ground source heat pumps are often referred to as geothermal or geo thermal heat pumps.

Ground and air source heat pump heating systems use electricity to heat and cool.  With the assistance of refrigerant, they can multiply the effectiveness of the electricity.  Heat pumps can produce 3-5 times the amount of heat that an electric furnace or space heater can using the same amount of electricity.

Ground Source Vs. Air Source Heat Pumps

Heat pumps get their name from the fact that they pump heat from one location to another.  When heating a home, they gather heat outside and pump it indoors.  They capture heat inside and dissipate it outside during an air conditioning cycle.  The major difference between air source and ground source heat pump heating systems is where they capture heat during a heating cycle and where they release heat when cooling.  Air source heat pumps, which are more common and less expensive, use refrigerant to capture heat from the air outside the home.

Geothermal heat pumps circulate a water-based solution through pipes underground or under water.  The natural heat in the earth, known as geothermal heat, warms the liquid in the pipes to approximately 55 degrees F and refrigerant captures the heat from it.  The reason ground source heat pumps are more efficient is that it is easier to capture heat from 55 degree water than it is to absorb it in very cold winter air.  When cooling, it easier to dissipate heat into 55 degree water than into hot, humid summer air.

The Components of Ground and Air Source Heat Pump Heating Systems

Look at the main components of a heat pump system:

• Refrigerant
  Heat pumps are so effective because refrigerant has the ability to absorb heat quickly and then shed the heat just as effectively.
• Coils
  When in heating mode, heat is captured either from the outside air or from the circulated water using refrigerant circulating through a coil.  The heated refrigerant is carried to a second coil where it is condensed, a process which forces it to shed the heat for use within the house. The process is reversed during a cooling cycle. The coils have special valves which cause the refrigerant either to expand and capture heat or condense and shed heat.
• Compressor
  According to the International Ground Source Heat Pump Association, the compressor in a ground source or air source heat pump heating system acts like a pump, circulating refrigerant between the coils so that it can capture heat and shed heat.
• Air Handler, or Indoor Furnace
  The heat that is shed by the refrigerant must be distributed throughout the house. The air handler containers a blower fan to pull unheated air into the system and across the hot coil, warming it and pushing it into the home.  For this reason, heat pumps are often referred to as a forced air type of home heating system.
• Duct Work
  Duct work is typically made from sheet metal. The duct work system uses supply ducts that carry heated or air conditioned air into the house and return ducts that carry untreated air to the system to be heated or cooled.
• Water Pump
  Geothermal heat pumps require a pump to circulate the liquid through the pipes to gather heat for heating or dissipate heat when cooling.

How Ground Source and Air Source Heat Pumps Work

When heating a home, the compressor pushes refrigerant into the outside coil in an air source heat pump.  In a geothermal heat pump, the refrigerant enters the coil that the water from the outdoor pipe is being circulated through.  The refrigerant is expanded into a gas and in the process it absorbs a large amount of heat either from the air or from the water.  As the refrigerant circulates, it comes back to the second coil where it is condensed into a liquid, forcing the heat energy to escape.  This makes the coil very hot.  The forced air system uses the blower fan to draw air into the air handler through the return ducts, passes it over the hot coil in order to heat it, and pushes it into the home via the supply duct work.

When the system is switched to air conditioning mode, the functioning of the refrigerant is reversed.  Heat is removed from the air inside the house which makes the coil very cold. The blower fan circulates air over the cold coil to cool it before pushing it into the house.  As outlined at the Energy Star website, the refrigerant transfers it to the outside coil in an air source heat pump where it radiates out of the coil and is dispersed by the fan.  In a ground source or geothermal heat pump, the heat is transferred into the water which is then cooled as it passes through the pipes underground or under water.

Duel Fuel, or Hybrid Heating Systems

As mentioned in the first paragraph, when a heat pump condenser (the outside unit) is matched to a gas or oil furnace inside the home, you have a wider flexibility of how to heat your home. This is commonly referred to as a dual-fuel system, since you can can use electricity on the heat pump down to roughly 30-35 degrees, and then switch to the gas or oil heating, for the more demanding times.

Air source and geothermal or ground source heat pump heating systems will play a larger role as they continue to become more affordable and more efficient.  The technology is improving with each new generation of products and more homeowners are considering them as they evaluate the right home heating system for their new or existing home.