What is a Heat Pump?
Heat pumps are a cost-effective way to heat and cool your home.
TVA offers a financing program through its eScore program that will allow customers to install high-efficiency heat pumps in their homes. Visit www.2escore.com to learn more!
Why choose a heat pump?
Simply put, a heat pump is the most cost-effective way to heat and cool your home in the Tennessee Valley. It's basically a central air-conditioning system that also works in reverse to provide central heating.
During the summer a heat pump takes the air in your home, makes it cool and dry, then re-circulates it. In the winter a heat pump pulls heat from air outside and pumps it indoors. Believe it or not, winter air actually contains heat you can use.
Heat pumps also deliver consistently even air flows, as opposed to hot blasts of air, for more comfort.
What should I consider when buying a heat pump?
Initial Costs vs. Operating Costs: The biggest expense over the life of a heat pump (or any heating and cooling system, for that matter) is not the cost of buying and installing it. It's the accumulated monthly cost of running it year after year. Usually, as the efficiency rating of a unit goes up, so does its initial cost. However, as the efficiency ratings go up, the monthly cost to operate the unit goes down. You'll want to consider the importance of a high-efficiency system and the trade-off between your initial cost versus the monthly operating cost.
Size: To work most efficiently, a heat pump's heating and cooling capacity has to match your home's heating and cooling demands. An undersized system won't adequately cool your home, while an oversized one won't dehumidify properly. A member of the Quality Contractor Network (QCN) can best tell you what you'll need. These heat pump contractors have all met the high standards set by TUB and TVA for participation in our heat pump program.
Duct System: This is very important because the heat pump will pump air all through your house using this system. The duct work must be insulated and sealed properly so the air gets where it's going at the right temperature. Proper construction of the duct work is essential to ensure efficient operation of the heat pump over the life of the system. Care taken in the initial construction and sealing of the duct work will yield maximum efficiency from the heat pump for years to come. Again, a member of the QCN can best tell you whether you'll be able to use your existing duct work or will need new ducts.
What are the parts of a heat pump?
All heat pumps are made up of four basic things. A compressor. The refrigerant. Two heat exchangers - one usually inside, the other outside. And most importantly, the reversing valve.
Compressor: The main part of the heat pump. It uses an electric motor to compress the refrigerant from a gas into a liquid and circulate it through the system.
Refrigerant: A chemical used to transfer heat. It changes from a liquid to a gas, or vice-versa, to either absorb or reject heat.
Heat Exchanger: You'll have two. The indoor exchanger absorbs heat in the summer and moves it outside. The outdoor exchanger absorbs heat from outdoors in the winter and brings it inside. This is also called a refrigerant coil.
Reversing Valve: The device in the refrigerating circuit that shifts to determine the appropriate cycle - heating or cooling. The valve reverses the flow of refrigerant allowing "heat pumping" in the proper direction, making the heat pump both a heating and cooling system.
What are the types of heat pumps?
Air Source Heat Pumps
This is the most common type of heat pump, and there are two basic kinds. The layout of your home will usually determine which one you'll want.
The 'packaged heat pump' is a self-contained unit that allows the compressor and both heat exchangers to be located outside your home. The unit uses duct work to heat and cool your entire home. Some special packaged heat pumps called 'packaged terminal,' 'self-contained through-the-wall,' and 'window heat pumps' are used for single rooms and don't need duct work.
The 'split system heat pump' is the more common of the two air source choices. Here, the indoor air handling unit and heat exchanger are separate from the compressor and the outdoor exchanger. This way, you have more options as far as how and where you install it. Whole-house heating and cooling happens via duct work.
The heating efficiency of an air source heat pump is measured as the Heating Seasonal Performance Factor (HSPF), and typically ranges from 6.6 to 9.1. Cooling efficiency for these heat pumps is indicated by the Seasonal Energy Efficiency Ratio (SEER), which typically falls between 10.0 and 15.0. The higher the number, the better the system.
Variable Speed Heat Pumps
Offering some of the newest advances in heating and cooling technology, variable speed heat pumps use a variable or multi-speed compressor that adjusts itself as temperatures change.
What that means is that this heat pump knows when it has to work harder to keep the temperature in your home consistent and does it automatically throughout the year. It's also a type of air source heat pump.
Unlike most heat pumps, the variable speed heat pump runs more often at lower speeds - making it exceptionally good at controlling humidity and offering more constant temperatures. It's also draftless and practically noiseless. You may not even be aware it's running.
And because it often runs at such low speeds, the variable speed heat pump also saves money. It's the miser's answer for a better heating/cooling system. And it's available in both "split" and "packaged" configurations.
Dual-Fuel Heat Pumps
With the dual-fuel heat pump you get the high efficiency of an electric heat pump in moderate temperatures, assisted by a gas furnace for supplemental heat in extremely low temperatures.
The unit monitors the temperature outside and adjusts itself accordingly, running the heat pump or the gas furnace automatically, to give you a consistently comfortable environment. Like the other air source and variable speed heat pumps, this one, too, is available as both a "split" and "packaged" option.
The dual-fuel heat pump offers the lowest possible heating costs in areas of the country where the temperature occasionally drops below freezing. Installation procedures are identical to those for conventional electric air-conditioning systems with gas heat.
Geothermal Heat Pumps
An Innovation Two Billion Years in the Making
Just a few feet under the surface, the ground maintains a relatively constant temperature. The earth stores 47% of the sun's energy, which is more than 500 times the energy mankind needs every year. So there's more than enough heat to go around. For years the question has been finding a means of tapping into this source.
At last, we have the answer: geothermal heat pumps. By transferring heat from the ground into the home, geothermal heat pumps produce nearly four times the energy they consume.
How geothermal works
When a geothermal heat pump is installed, a series of pipes, called a loop, are buried underground. These pipes hold a fluid that absorbs the ground's heat. Once this fluid is carried inside, compressors and heat exchangers concentrate this heat so it can be released into the house at a warmer temperature. A well-designed duct system delivers that warm air throughout your home.
In the summer, this process is simply reversed. Excess heat is drawn from the house and reabsorbed by the ground.
Free heat means free hot water
With the addition of a desuperheater, some geothermal systems can provide all or part of your home's hot water. A desuperheater is a small water heater device which uses refrigerant from a heat pump's compressor to heat water. Once heated, this water circulates to the home's water heater. In the summer, the water heater uses the excess heat that would otherwise be sent back into the ground.
A conventional water heater will be used if the desuperheater doesn't produce enough, or if the geothermal pump is turned off. But when the geothermal pump is running frequently, a family can get their hot water virtually for free.
Other benefits of a geothermal beat pump
Efficiency:Without a doubt, geothermal heat pumps are the most efficient heating and cooling system you can buy. The reason is simple. A conventional gas furnace must burn fuel just to create heat. While a furnace wastes energy creating heat, a geothermal system uses energy to move and compress existing heat which is renewable energy from the ground.
Cost-effectiveness:The U.S. Environmental Protection Agency estimates that, compared to conventional systems, geothermal heat pumps save homeowners 30-70 percent in heating costs, and 20-50 percent in cooling costs. So, on average, the initial cost of installing a geothermal heat pump can be recovered in three to five years. Pay a little more up front, save a lot more down the road.
Durability: The savings won't end with your heating and cooling bill. This system is highly reliable. Since it has no defrost cycle, there is less wear on critical components and no loss of operating efficiency. Housed indoors, the geothermal heat pump isn't subject to harsh weather conditions. So it requires little maintenance, and can last for many years.
Comfort: A geothermal heat pump lets you live in comfort. By heating and cooling in an even fashion, it eliminates hot and cold spots. And since a geothermal system doesn't generate air as hot as a gas furnace, your home maintains a comfortable level of humidity.
Environmental safety: Geothermal heat pumps help minimize environmental threats posed by the burning of fossil fuels, like acid rain, air pollution, and the greenhouse effect. And because the geothermal heat pump has no outdoor components, it won't add to noise pollution. In fact, you won't even be able to tell when it's on.
Allergy resistant: If you have allergies or asthma, a furnace won't do you any favors. But since a geothermal system doesn't require make-up air for combustion, spores and pollen won't be drawn into your house during allergy season. And since a geothermal system runs longer than a gas furnace, it filters the air more. And filtered air is clean air.
Cleanliness: A geothermal system won't add combustion by-products into your home. There are no pilot lights, no chimneys, no odors, no fumes. And no worries.
Customer satisfaction: If you're still not convinced that a geothermal system is right for you, ask someone who owns one. A survey published by the National Rural Electric Cooperative Association found that 97% of geothermal system owners would purchase one again, and 99% would recommend one to a friend.
Types of Loops
Horizontal Ground Closed Loops: If you have the room, this system is your best option. The shallow trenches are easy to dig, making this system cost-effective. But it is best installed when a house is under construction. Expect every ton of heating and cooling capacity to require 400 to 600 feet of pipe.
Vertical Ground Closed Loops: This system is a good choice if yard space is insufficient, the ground is too rocky, or you want to retrofit with minimal landscape disruption. Vertical holes, between 150 and 450 feet deep, are bored into the ground. Each hole contains a single loop of pipe with a U-bend at the bottom. These vertical pipes are then attached to a horizontal pipe which connects to the house. This system is more expensive to install. But it does require less pipe, because temperatures are constant deeper underground.
Pond Closed Loops: If you live near a body of water, this is your most economical option. However, to ensure sufficient heat transfer, this system should only be installed if the water level never drops below six feet. This system has no adverse effect on the pond.
Open Loop System: When groundwater is plentiful, this system is the simplest to install. Groundwater from an aquifer is piped directly into your home. Once the water leaves your home, it's pumped back into a second well. Local environmental officials should always be consulted when this system is being considered.
Standing Well System: This system draws temperate water from the bottom of a well, circulates it through the heat pump's heat exchanger, and returns it to the top of the same well. This well usually also provides potable water. Good water quality and suitable well design are required.
A few tips before purchasing a system
Look for equipment that is certified by the Air Conditioning and Refrigeration Institute, a non-profit organization rating residential and small commercial systems.
To ensure a high-quality system, make sure any performance guarantee is for a completed heat pump system covering the equipment and installation, and is not limited to the heat pump itself.
If your system is too large, it will waste energy, and it won't provide proper humidity control. So be sure that your contractor determines your home's heating and cooling requirements by using accepted measures, such as those recommended by the Air Conditioning Contractors Association. The actual size of your system should be within 15 percent of the calculated load.
Consult the Quality Contractor Network for an experienced contractor. The contractor should select the size of your system, the type of loop, and the fluid to be circulated in the loop. In addition, the contractor should examine your home to make sure it is as energy-efficient as possible. Homes that are more energy-efficient require smaller systems.
Enjoy tomorrow's heater today
Geothermal heat pumps are fast becoming the system of choice all over the country. However, because more builders and contractors now offer the systems, costs have dropped substantially. Today, homeowners in all tax brackets can enjoy this technology.
To learn more about installing a geothermal heat pump for your home, visit the Geothermal Heat Pump Consortium Website at www.energyright.com.