Buying A Geothermal Heat Pump

A new Energy Star specification for geothermal heat pumps went into effect on December 1, 2009. The new specification allows water-to-water GHPs to immediately be eligible to qualify for the label. On average, Energy Star qualified products covered under this new specification will be over 45 percent more energy efficient than standard options.

Geothermal Heat Pump

Geothermal Heat Pump

  • Anticipating advances in technology in the coming years, the US Environmental Protection Agency has set more stringent efficiency requirements to ensure that Energy Star continues to represent top performers in this category.
  • New requirements for water-to-air and direct geoexchange GHP models will take effect on January 1, 2011. Even more stringent levels will go into effect for water-to-water and water-to-air models on January 1, 2012.
  • As of December 1, 2009 homeowners who install geothermal heat pumps with the Energy Star are eligible for a 30 percent federal tax credit. Learn more.

What should I look for when buying a geothermal heat pump?

Although these products can be more expensive to purchase up front, the cost difference will be paid back over time through lower energy bills, which is why it is important to look for the Energy Star label to make sure you re getting the most efficient, and thus most money-saving unit possible.

When buying new equipment, sizing and installation are as important as product quality.

Sizing and Installation

Your new heating and cooling system should be a custom fit for your home. Sizing and a handful of other installation practices can dramatically affect how well your new equipment will deliver comfort and savings. Expect to pay a little more for a good contractor who follows these practices.

Calculate the size of equipment

For starters your new furnace, boiler, heat pump or air conditioner should be sized to fit your home. You can request a copy of the design load calculation used to determine the right size of equipment for your home. Some contractors will use rules of thumb to size your air conditioner, but rules of thumb can overestimate the size needed. A good contractor will use a design load calculation to size a central air conditioner to your home. The contractor will need to check the following six factors.

How well your house is insulated

By adding the proper amount of insulation to your walls and ceiling or attic, your house will require less cooling. By insulating before you purchase an air conditioner, you'll save twice- once when your energy bills drop and again when you need a smaller, less expensive air conditioner.

How well air leaks are sealed

A well-sealed house limits the amount of hot, humid air that gets inside. In many homes the air leaks can add up to as much as an open window. Sealing air leaks and adding insulation can reduce heating and cooling cost by 20%.

How well your ducts are sealed and insulated

Ducts carry cooled air from your air conditioner to where it is needed. Under-insulated ducts actually heat up, which reduces the amount of cool air that gets to you. Leaky ducts can cause your heating and cooling system to work harder to keep your home at a comfortable temperature.

The size, type and number of windows and the direction they face

The size, type and number of windows are huge factors in determining your cooling needs. Thoughtful landscaping and overhangs can greatly decrease the temperature in your house by affecting the amount of sunshine that comes through your windows. In central and southern climates, ENERGY STAR qualified windows can reduce heat gain from the sun by 45 to 60 percent.

Shading provided by overhangs and landscaping

Leafy trees can reduce unwanted heat in the summer, but allow the warmth of the sun to come in when they drop their leaves in the winter. Well-positioned overhangs will also block the sun's heat in the summer, but allow the sun light to come in during the winter to warm your home.

The size, layout, and orientation of your house

The size of a house's walls and roof and their positions in relation to the sun are important factors in sizing an air conditioner.

To complete the design load calculation the contractor will need to take measurements during the initial visit to your home and ask you some questions. The calculation is usually done using software, and should be based on professional guidelines such as Manual J from the Air Conditioning Contractors of America (ACCA) or similar method. Oversized equipment can cause reduced comfort and excessive "air" noise. Oversizing will shorten the life of the equipment by causing it to cycle on and off more frequently than a properly-sized unit. Undersized equipment, with airflow that is too low, can reduce the efficiency of the air distribution and accelerate wear on system components, leading to earlier failure.

After the design load calculation is completed, ducts, supply registers, and return grilles can be sized and selected using professional guidelines in ACCA's Manual D or similar method.

Seal and insulate ducts in attics and crawlspaces

If you’re installing a central air conditioner, furnace or heat pump ask your contractor about the condition of your air ducts. A good contractor should be able to test your air ducts to identify and seal leaks.

  • Duct sealing should be done by a professional using mastic, metal-backed tape or aerosol-based sealing.
  • In some instances, your contractor may advise you that it is necessary to replace or add ducts. If there are insufficient supply registers or return air grilles in your home, it may be necessary to install additional ducts to accommodate the need for registers or grilles. When possible ducts should be located within conditioned space. If the ducts must be in unconditioned space (attic or crawlspace) they should be insulated.

Check and correct airflow

For central air conditioners, furnaces or heat pumps there is an optimal air flow for comfort and savings.

  • If airflow is too high, duct leakage increases and the temperature at the register is not sufficient for optimal home comfort.
  • If airflow is too low, distribution efficiency drops and accelerates the wear on system components leading to premature failure.

A good contractor will test the air flow of your heating and cooling system and make adjustments for optimal performance. Typically, testing and adjustments should be done after duct leakage repairs have been completed.

Proper refrigerant charging

If your are installing a new central air conditioner or heat pump you should know that recent field studies suggest that approximately 75% of installed cooling equipment may have incorrect amount of refrigerant. Incorrect refrigerant level can lower efficiency by 5 to 20% and can ultimately cause premature component failure, resulting in costly repairs that could have been prevented. A good contractor will use one of three methods, recommended by equipment manufacturers, to verify the correct refrigerant level. These methods include super-heat, sub-cooling, or weigh. Ask your contractor how they verify the refrigerant level is correct.

In addition, you should know that since 1992, in order to protect the earth's atmosphere (ozone layer), all technicians must be certified to handle refrigerant. Ask them to show you proof of refrigerant handling certification.

Equipment placement

Placement of new equipment is unique for every home, but a good contractor should follow manufacturer's installation instructions for best results. For example, Indoor equipment should be installed in conditioned space, or a space that is well insulated. The Outdoor compressors should be placed out of the sun and kept free of debris. Equipment should be installed in an accessible area for easy maintenance. Allow plenty of room for free airflow on all sides of the equipment. Thermostats should be placed away from direct sunlight, drafts, doorways, skylights and windows.

Energy Efficiency Requirements for Geothermal Heat Pumps

NOTE: Tier 1 requirements became effective December 1, 2009. The second phase of this specification, Tier 2, shall become effective January 1, 2011.

Table 1: Tier 1 Requirements (Effective December 1, 2009)
Product Type EER COP
Water-to-Air
Closed Loop Water-to-Air 14.1 3.3
Open Loop Water-to-Air 16.2 3.6
Water-to-Water
Closed Loop Water-to-Water 15.1 3.0
Open Loop Water-to-Water 19.1 3.4
DGX
DGX 15.0 3.5
Table 2: Tier 2 Requirements (Effective January 1, 2011)
Product Type EER COP
Water-to-Air
Closed Loop Water-to-Air 16.1 3.5
Open Loop Water-to-Air 18.2 3.8
Water-to-Water
Closed Loop Water-to-Water 15.1 3.0
Open Loop Water-to-Water 19.1 3.4
DGX
DGX 16.0 3.6
Table 3: Tier 3 Requirements (Effective January 1, 2012)
Product Type EER COP
Water-to-Air
Closed Loop Water-to-Air 17.1 3.6
Open Loop Water-to-Air 21.1 4.1
Water-to-Water
Closed Loop Water-to-Water 16.1 3.1
Open Loop Water-to-Water 20.1 3.5
DGX
DGX 16.0 3.6

Models must meet or exceed the energy efficiency ratio (EER) and coefficient of performance (COP) values in the tables above.

The specifications in the charts above apply to single stage models. Multi-stage models may be qualified based on:

  • EER = (highest rated capacity EER + lowest rated capacity EER) / 2
  • COP = (highest rated capacity COP + lowest rated capacity COP) / 2

Note:
Commercial (i.e., 3-phase) units are not eligible for qualification under the ENERGY STAR specification at this time.

Test Procedures:

AHRI 870 for DGX systems.

ISO 13256-1 for water-to-air models (open and closed loop systems).

ISO 13256-2 water-to-water models (open and closed loop systems).

Definitions:


Geothermal Heat Pump

A geothermal heat pump uses the thermal energy of the ground or groundwater to provide residential space conditioning and/or domestic water heating. A geothermal heat pump model normally consists of one or more factory-made assemblies that include indoor conditioning and/or domestic water heat exchanger(s), compressors, and a ground-side heat exchanger. A geothermal heat pump model may provide space heating, space cooling, domestic water heating, or a combination of these functions and may also include the functions of liquid circulation, thermal storage, air circulation, air cleaning, dehumidifying or humidifying. A geothermal heat pump system generally consists of one or more geothermal heat pump models, the ground heat exchanger(s), the air and/or hydronic space conditioning distribution system(s), temperature controls, and thermal storage tanks.

Single-Stage

Geothermal heat pumps that are designed to operate at one stage and one capacity.

Multi-Stage

Geothermal heat pumps that are designed to operate at more than one stage or capacity through the use of technologies such as multiple stage compressors, dual compressors, variable speed compressors, etc. Multi-stage models are more efficient while running at lower capacities, but have the capability to supply more heating or cooling using higher capacities when required.

Closed Loop

A ground heat exchange method in which the heat transfer fluid is permanently contained in a closed piping system. Also called a ground-loop system.

Open Loop

A ground heat exchange method in which the heat transfer fluid is part of a larger environment. The most common open loop systems use ground water, reclaimed water, or surface water as the heat transfer medium. Also called a ground-water system.

Water-to-Air

A geothermal heat pump model that provides space conditioning primarily by the use of an indoor air heat exchange coil. Water-to-air models may also provide domestic water heating and hydronic space heating by using desuperheater and/or demand water heating functions.

Water-to-Water

A geothermal heat pump model that provides space conditioning and/or domestic water heating by the use of indoor refrigerant-to-water heat exchanger(s). Water-to-water models may provide domestic water heating by using desuperheater and/or demand water heating functions.

Direct Geoexchange (DGX)

A geothermal heat pump model in which the refrigerant is circulated in pipes buried in the ground or submerged in water that exchanges heat with the ground, rather than using a secondary heat transfer fluid, such as water or antifreeze solution in a separate closed loop.

Coefficient of Performance (COP)

A measure of efficiency in the heating mode that represents the ratio of total heating capacity to electrical energy input. For the purpose of this specification, COP will be calculated for closed loop and open loop systems in accordance with the International Standards Organization (ISO) Test Standard 13256-1 or 13256-2 as stated in Section 5 below. For DGX systems, COP will be calculated in accordance with the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) 870 conditions.

Energy Efficiency Ratio (EER)

A measure of efficiency in the cooling mode that represents the ratio of total cooling capacity to electrical energy input. For the purpose of this specification, EER will be calculated for closed loop and open loop systems in accordance with ISO 13256-1 or 13256-2 as stated in Section 5 below. For DGX systems, EER will be calculated in accordance with AHRI 870 conditions.

Which units qualify for the Energy Star rating?

ENERGY STAR Geothermal Heat Pumps (WatertoAir and DGX) Product List [PDF 224Kb]

ENERGY STAR Geothermal Heat Pump (Water-to-Water) Qualified Product List [PDF 72Kb]

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