Terms
BTU: British Thermal Unit2
The quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit at a specified temperature.
EER: Energy Efficiency Ratio
A measure of the efficiency of a heating or cooling system, as a heat pump or air conditioner, equal to the ratio of the output in BTU/hour to the input in watts.
Compressor
Outdoor part of an air conditioner or heat pump that compresses and pumps refrigerant to meet household cooling requirements.
Air Handler
Indoor part of an air conditioner or heat pump that contains a fan or blower to move cooled/heated air throughout the ductwork of a home.
SEER: Seasonal Energy Efficiency Ratio
Is a ratio of the total cooling capacity during normal periods of operation divided by the total electric energy input during the same time period. A higher SEER rating means the cooling unit will produce more using less electricity.
AHRI: Air-conditioning, Heating, & Refrigeration Institute3
Is an association with a certification program for unbiased evaluation of heating, water heating, ventilation, air conditioning, and commercial refrigeration equipment and develops industry-recognized performance standards for industry equipment.
COP: Coefficient of Performance1
is the efficiency expressed as the amount of heat removed from a substance being refrigerated divided by the amount of work necessary to remove the heat. For example, a heat pump working in the summer with a COP of 2.0 will deliver twice amount of cooling than the amount of electricity it uses.
Different Types of Systems
Air Conditioner
According to EIA.gov, Air conditioners in Indiana can account between 5% and 12% of energy expenditures depending on which part of Indiana you live.4 Air conditioners utilize a refrigerant that when evaporated over the indoor coils, pulls heat from inside a home and expels it outside into the condenser. To learn more, visit the Department of Energy website5.
Heat Pump
Air-source heat pumps are the most common heat pump out in the market. Heat pumps can deliver up to 10 to 15 times as much energy as they consume driving the compressor.
Air-Source Heat Pumps
Have an outdoor unit (heat pump) and an indoor unit (air handler) that connects to the ducts that send the heated/cooled air to your vents. The indoor/outdoor units are connected by tubing that circulates refrigerant back and forth absorbing or releasing heat depending on the thermostat settings. While very efficient in warmer climates, colder climate heat pumps can also include an axillary heating component for temperatures that dip below the efficiency of the heat pump.
As described by Allison Bailes in his article How Does a Heat Pump Get Heat From Cold Air6; “The refrigerant is pushed through the expansion valve, and the temperature of refrigerant drops – a lot. The refrigerant going through the outdoor coil (the evaporator) is usually 10 to 20 degrees Fahrenheit lower than the temperature of the outdoor air. So, that cold outdoor air is actually the warmer object when it comes in contact with the outdoor coil of a heat pump in heating mode…Once we get that heat from the air into the refrigerant, its just a matter of bringing it into the house and then transferring it into your home’s air.”
Water (Chiller) Type Heat Pumps
Work similar to air-source heat pumps except rather than circulating refrigerant back and forth, it collects heat from water that is pumped between the evaporator and condenser to heat and cool the home.
Ductless Mini-Split Heat Pump
Works very similar to the air-source heat pump. Ductless mini-split heat pumps have an outdoor unit (condenser/heat pump) and indoor air handling units that can be installed on the wall of each room or the ceiling. Each air handling unit can be managed by remote.The air handlers in a mini-split provides heated/cooled air directly from the air handlers thereby reducing the heating/cooling losses seen from air traveling through ducts.
Geothermal
Geothermal heat pumps (GEO’s) work similarly like an air-source or chiller heat pump except it draws from the constant temperature beneath the ground instead of the outside air temperature. Most GEO installs are closed-loop systems where a water based solutions runs through tubing buried underground or submerged in water. The trenches for the tubing can be up to 500 feet long.While Geo’s are more expensive to install, they can last between 25 to 40 years and depending on the cost of energy and available incentives, your payback may only be 5 to 10 years.
Electric Furnaces
Are very similar to a hair dryer. It uses electricity to heat up the air brought in with the blower with a heating element. Then the blower pushes the hot air through the duct works in your home.Electric furnaces are more expensive to operate than other electric resistance systems because of their duct heat losses and the extra energy required to distribute the heated air throughout your home (which is common for any heating system that uses ducts for distribution).Heated air is delivered throughout the home through supply ducts and returned to the furnace through return ducts. If these ducts run through unheated areas, they lose some of their heat through air leakage as well as radiation and convection from the duct’s surface7.
Gas Furnaces
Use propane or natural gas to send heat to a metal heat exchanger. The furnace’s blower pushes the cold air over the metal heat exchanger and into the ductwork sending hot air throughout your home. The colder air is drawn back into the furnace through the return ducts to be blown over the metal heat exchanger once again. The gases produced by the combustion of natural gas is vented outside through the flue.Today’s gas furnaces are built more efficiently with some qualifying at 97% AFUE rating. The higher the AFUE rating, the more the gas furnace will cost and depending on gas prices, where you live, and how well your home is insulated will affect your payback.
Dual Fuel Heat Pumps
Are very similar to air-source heat pumps with one difference. When the temperature outside is below the efficiency level of the heat pump, the thermostat will start the backup gas-fired furnace system. This will often be listed as “emergency heat” or “auxiliary heat”.
Here are some common questions and tips for your HVAC system.
When You Should Replace Your HVAC Unit
- If your HVAC unit is more than 10 to 15 years old.
- If your system needs frequent repairs or is abnormally noisy.
- If your energy bills are increasing even though your usage isn’t.
What To Look For In Your New HVAC Unit
- Sizing is important when looking for your next HVAC unit. If a system is too large or too small for your heating/cooling space, efficiencies will be lost and utility cost may go up.
- When determining what size heat pump for a home, there are several factors to consider. Climate, size of the heat/cooling space, your home’s foundation, insulation value, air filtration, whether your home is heavily shaded or gets lots of sun, etc.
- General rule of thumb is 1 to 1.5 ton for every 1,000 square feet of space but to ensure you are getting the right size heat pump, a professional HVAC contractor will utilize all collected information from your home to calculate the right size.
- How efficient the heat pump is. When looking for efficiency ratings whether for the heating component (HSPF) or the cooling component (EER), the higher the rating the more efficient it is.
- If considering incentive rebates with your local utility, make sure your heat pump’s efficiency rating qualifies.
What To Look For When Selecting A Contractor
- Ask to see the HVAC License and certifications that are required by Indiana.
- Research their company – stability in the business indicates a contractor is doing something right8.
- Ask the company if they offer tool programs and training for their employees. This will give you insight to whether they may be a company that subcontracts out their installations putting you at the mercy of whatever your installer decided to purchase for the job.
- When performing a consultation, the HVAC contractor should be evaluating the whole home. From square footage of the home to how many windows a home has and which way they are faced along with much more information.
- Ask for references and referrals and don’t be shy to call up and verify the references. Ask the references if the job was completed on time and within budget. Did the company test the system after installation to ensure its maximum efficiency?
- Check the business with the Better Business Bureau website and against other popular review websites.
- Ask friends, neighbors, co-workers for an HVAC contractor they have used.
Maintaining Your HVAC
- Get it serviced at least annually (see our Rebates page for more information on our HVAC tune-up incentive).
- Change your filters monthly.
- Keep area around condenser clear from grass/weeds, debris, etc.
- Do not put anything on your condenser that could reduce the air it needs to take in to cool itself.
- Do not store stuff around the furnace.
- Vacuum around the furnace to keep dust from collecting.
Sources 1Dictionary Coefficient of Performance 2Merriam Webster British Thermal Unit 3AHRI About Us 4eiaToday in Energy 5Department of Energy Air-Conditioning 6Green Building Advisor How Does a Heat Pump Get Heat from Cold Air 7Department of Energy Electric Resistance Heating 8Air Authority Top 5 Things to Look for When Choosing an HVAC Contractor