Heat Pumps & Geothermals

2 Types of Electric Heat Pumps

Air-Source Heat Pump

• Air-source heat pumps look similar to an outdoor air conditioner
• To heat a house, it gathers heat from the outside air, and moves that heat inside a house to keep it warm
• To cool the home, it gathers the heat from inside and gets rid of it by sending it outside
• In the winter (when temps go below 32º F), air-source heat pumps can have trouble gathering heat from the cold winter air, and in the summer, sending warm air out into warm air

Ground-Source (Geothermal) Heat Pump

• Super-efficient geothermal heat pumps provide clean, quiet heating and cooling while cutting utility bills by up to 70%
• A ground-source or geothermal, heat pump functions like a conventional heat pump, moving heat between indoors and out
• The difference is that geothermal heat pumps transfer heat to and from the ground, via long loops of liquid-filled pipe buried in the ground
• The temperature underground stays around 50º F no matter how hot or cold it gets outside
• An air-source heat pump struggles to scavenge heat from freezing winter air or to dump it into the summer swelter
• A ground-source heat pump has the comparatively easy job of extracting and disbursing heat through the 50º F liquid circulating in its ground loop
• Geothermal systems are twice as efficient as the top-rated air conditioners and almost 50% more efficient than the best gas furnaces

What it Costs

• $15,000 to $20,000 installed for the system, including ground loops, heat pump, and controls
• The Database of State Incentives for Renewable Energy provides up-to-date information on state incentive programs

Geothermal Closed-Loop Heat Pump (Geothermal System)

There are 2 main components to the geothermal system:

• The buried closed-loop (a loop of pipe buried in the ground)
• The indoor unit which is tied into a proper ductwork system
• There is no outdoor unit used with this system as you would find with an air-source heat pump system

Buried Closed-Loop

• Heat is exchanged with the earth by using a buried earth loop and a small circulating pump
• Only 2 types of pipe are acceptable for the earth loop – polybutylene and high-density polyethylene pipe
• This earth loop must be installed by a certified contractor
• The loop is carefully assembled on location using “heat fusion” to join the pipes where necessary
• Once assembled, the loop system becomes “one piece” of pipe with parallel circuits
• The integrity of this loop is such that a virtual lifetime of trouble-free use can be expected
• Installation by any other means may cause a failure of the pipe because of the unique conditions below the ground

Heating Mode

• Water, with an antifreeze solution, is circulated through the earth loop
• In the heating mode, the indoor unit extracts heat from the solution in the loop, and with a refrigeration process, intensifies that heat and delivers it through the duct system at temperatures ranging from 95 to 105º F
• Since heat is being transferred – not produced – the geothermal system is delivering over 3 units of energy for every unit of energy it consumes
• This is possible due to the fact that it takes advantage of below-ground temperatures that are warmer in the winter and cooler in the summer than the outdoor air
• Since the earth loop is buried in the ground, where temperatures are constant, the outdoor temperature does not adversely affect the high efficiency of the geothermal system

Cooling Mode

• In the cooling mode, the indoor unit extracts heat from the air inside the home, and transfers that heat into the solution circulating through the loop
• The heat is then rejected to the earth
• It is much easier to transfer heat into the cooler earth than trying to transfer it into the 90º F to 100º F outdoor air

Domestic Hot Water (Desuperheater)

• Most manufacturers offer an option that produces a large percentage of the annual hot water requirements
• A “Desuperheater” is installed with a small circulating pump between the existing water heater and the geothermal system
• “Desuperheaters” are becoming a standard
• During the winter, when the geothermal system is operating in the heating mode, hot water is being produced at the same high efficiency
• In the summer, the heat that is being rejected by the geothermal system is transferred to the water heater at little or no cost