Glossary Of Terms

The HVAC industry can be a maze of unfamiliar acronyms and industry terms. This dictionary will help you navigate the most common terms you’ll come across during your buying decision.

A
AC Alternating Current - A type of current where the polarity is perpetually reversing, causing the directional flow in a circuit to reverse at regular intervals.
ACCA - Air Conditioning Contractors of America.
Acoustical - Relating to sound, the science of sound, or a sense of hearing.
AFUE - Annual Fuel Utilization Efficiency. A measurement used to rate furnace efficiencies by dividing the ratio of heat output by heat input.
AGA - American Gas Association, Inc.
Air Conditioner - A device that changes humidity levels, temperature or quality of air.
Air Flow Volume - Measured in cubic feet per minute (cfm), this is the amount of air circulated in a space.
Air Handler - Parts of a system including the fan-blower, filter and housing.
ARI - Air Conditioning and Refrigeration Institute.
ASHRAE - American Society of Heating, Refrigeration and Air Conditioning Engineers.

B
BTU - British Thermal Unit. Measures the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit.
BTUh - British Thermal Units per hour.
Burner - The device that facilitates the combustion of air and gas.
Burner Orifice - The opening in the burner through which the gas or fuel passes prior to combustion.

C
Capacity - HVAC capacity is the output produced by the heating or cooling unit and is measured in BTUs per hour.
Celsius - A temperature scale that registers the freezing point of water as 0° and the boiling point as 100° under normal atmospheric pressure.
CFM - Cubic Feet per Minute. A measurement of airflow volume.
Charging a System - Adding coolant, or refrigerant, to an HVAC system.
Compressor - A pump that increases the pressure of gas.
Condensate - Vapor that is turned into a liquid as its temperature is lowered.
Condenser Coil - Also an outdoor coil. A device that removes heat from the refrigerant, allowing the refrigerant to be converted from vapor to liquid.
Condenser Fan - A fan that passes air over the condenser coil to facilitate the removal of heat from the refrigerant.
CSA - Canadian Standards Association.

D
DC - Direct Current. A type of electrical current that only flows in one direction.
Damper - Found at the exit point of ductwork, this plate usually contains grates that can be opened or closed to control the flow of air into a zone.
Degree-Day - Calculated by subtracting the average outdoor temperature for an area from 65º Fahrenheit. This measurement is used to estimate the amount of heating or cooling a home or building will need.
Dehumidifier - A device that removes humidity, or moisture, from the air.
Diffuser - A grille over an air supply duct with vanes that distribute the discharging air in a specific pattern or direction.
DOE - Department of Energy.
Downflow Furnace - A furnace with an intake on the top and an air discharge at the bottom.
Drain Pan - Also a condensate pan. As the refrigerant vapor is liquefied, the drain pan collects the condensate and funnels it to the drain line.
Dry Bulb Temperature - The temperature as measured without the consideration of humidity.
Ductwork - A network of metal, fiberboard or flexible material flowing throughout a space which delivers air from an HVAC unit to the respective zones of a home or office.

E
EER - Energy Efficiency Ratio.
EPA - Environmental Protection Agency.
Expansion Valve - A valve that meters the levels of refrigerant through a temperature or pressure control.
Evaporator Coil - Also an indoor coil. A device that is designed to absorb heat in the air in order to change the liquid refrigerant that flows through it into a vapor.

F
Fahrenheit - A temperature scale in which water freezes at 32 degrees and boils at 212 degrees at normal atmospheric pressure.
Fan - A device that creates air flow.
Filter - A device that acts like a strainer to remove dirt or undesired particles.
Flue - A vent that removes the byproducts of combustion from a furnace.
Furnace - The major component in heating a home. A device that facilitates the combustion of fuel and air to create heat.
Fuse - A delicate metal strip connecting two parts of an electrical circuit. This strip breaks, or melts, in the event of excess electrical charge, breaking the electrical circuit.

G
GAMA - Gas Appliance Manufacturers Association.

H
Heat Exchanger - A device through which heat is transferred to a cold area or surface.
Heat Gain - The amount of heat added or created in a designated area.
Heating Coil - A coil that acts as a heat source for a heating system.
Heat Loss - The amount of heat subtracted from a designated area.
Heat Pump - A device used for either the heating or cooling of a space by transferring heat between two reservoirs.
Heat Transfer - Moving heat from one location to another.
HSPF - Heating Seasonal Performance Factor. This factor rates the efficiency of the heating portion of the heat pump.
Humidifier - A device that adds humidity, or moisture, to the air.
Humidistat - The device that measures humidity and turns the humidifier on and off.
Humidity - Dampness in the air caused by water vapor.
HVAC - Heating, Ventilation and Air Conditioning.

I
Ignition - Elevating the temperature of a substance to the point of causing a combustion reaction.

K
Kilowatt (kW) - 1,000 watts.

L
Latent Heat - A type of heat that when added to an area produces an effect other than an increase in temperature.

M

Media - The fine material of a filter that traps dirt, dust, mildew or bacteria.

N

NEC - National Energy Council / National Electric Code.
NEMA - National Electrical Manufacturing Association.

O
Orifice - An opening or hole.

P
Package Unit - A heating and cooling system contained in one outdoor unit.
PSI - Pounds per square inch.
PSIA - Pounds per square inch, absolute.
PSIG - Pounds per square inch gauge.
PVC - Polyvinyl chloride; a type of plastic.

R
Reciprocating Compressor - A type of compressor used in cooling systems to compress refrigerant by using a piston action.
Refrigerant - A chemical that condenses from a vapor to liquid and, in the process, decreases in temperature.
Refrigerant Charge - The amount of refrigerant in a system.

S
SEER - Seasonal Energy Efficiency Ratio. A rating system developed by the U.S. Government to indicate the efficiency level of cooling equipment.
Self-contained System - A package unit.
Sensible Heat - Heat added or subtracted that causes a change in temperature.
Sensor - A device that reacts to a change in conditions.
Split System - An outdoor unit combined with an indoor unit.

T
Thermostat - Sensors that monitor and control the output of an HVAC system.
Thermostatic Expansion Valve - A device that creates a constant evaporator temperature.
Ton - One ton is 12,000 BTUs per hour.

U
Upflow Furnace - A furnace that pulls in air from the bottom and releases it through the top.

V
Vacuum - A space where the pressure is significantly below that of standard atmospheric pressure.
Volt - A unit of electro-motive force.
Voltage - The force pushing electrical current along wires and cables.

W
Watt - The unit of electrical power equal to the flow of one amp at a potential difference of one volt.
Wet Bulb Thermometer - A thermometer that measures the relative humidity in the air

Z
Zoning - A system that divides a home, office or space into different regions in order to better control the temperature and effectiveness of a heating and cooling system.

• Q:  My Heat Pump seems to be running to much to keep the house cool, Why?

  It could be possible you have a freon leak or just low and the A/C needs more freon to create theproper temp to cool your house. This can be a very simple repair and your HVAC system needs a charge. If you leave it alone your system will have high electric costs to run.

  Q: When should I use my Emergency Heat?
  The Emergency Heat switch on a Heat Pump thermostat confuses many people. The fact of the matter is that most people don't seem to understand exactly what Emergency Heat is and when they need to use it. Many people think that Heat Pumps don't work in cold weather and they are supposed to use the emergency heat whenever it gets really cold... Wrong!

  
  Q: What is Emergency Heat?
  Simply put, all Heat Pumps in northern climates [below 35 degrees] need a supplemental heating source. Usually it is in the form of electric resistance heating. This is an all-electric Heat Pump. It can be a gas, oil, or hot-water back-up system as well. The supplemental heat is also referred to as "second-stage" or "back-up" heating, "first-stage" being the Heat Pump only. The supplemental heat is also what is used as the Emergency Heat.
  
  Different systems have different ways of determining when the second-stage comes on to assist the heat pump but it is always done automatically. So the two stages will work together in the colder months and it is not necessary to switch your thermostat to Emergency Heat. Now we know what supplemental heat is and that it is also used for Emergency Heat.

  Q: Its Cold outside. the red light on AUX/Emergency is on much of the time.  I want to slow that down.

  As spoken in the above referenced paragraph explaining Heat Pumps and their auxiliary heating emergency heating mode. You have to use some logic now and some good practical thinking. Once the temperature drove drops below 37-35° engaging your auxiliary Emergency heating mode on.

What is a Heat Pump?

A heat pump is a machine or device that moves heat from one location at a lower temperature to another location at a higher temperature using mechanical work or a high-temperature heat source. The difference between a heat pump and a normal air conditioner is that a heat pump can be used to provide heating or cooling. Even though the heat pump can heat, it still uses the same basic refrigeration cycle to do this. In other words a heat pump can change which coil is the condenser and which is the evaporator. A reversing valve normally achieves this. In cooler climates, it is common to have heat pumps that are designed only to provide heating.

In the summer, a heat pump removes heat from inside your home and replaces it with cool air. Simply speaking, it works just like a conventional, high-efficiency air conditioner.

In the winter, the system works in reverse. It removes available heat from the air outside your home (yes, there is heat in cold outdoor air) and moves it indoors, providing an even, comfortable temperature level throughout your home. Seldom are there any warm or cold spots such as those exist when a gas furnace alone is used.

When outdoor temperatures drop below 20 degrees or so, a back-up heating system -- usually an existing gas furnace -- automatically provides supplemental heat. Studies show that in the OPPD service area, winter temperatures are below 20 degrees only about 15 percent of the heating season. That means that a heat pump provides sufficient heat for about 85 percent of the heating season. That's more than enough time to help you save energy and save money on your annual heating and cooling costs.

Questions and Answers
Frequently Asked Questions About Heat Pumps
How do I know if I can use an add-on heat pump with my furnace? An add-on heat pump can be installed in both new and existing homes, whether the furnace operates on natural gas, oil, propane or electricity. In most cases, the ductwork will be the same.
Is it true that a heat pump runs longer than a furnace? Yes. That is because a heat pump heats your entire home more evenly, unlike a gas furnace that delivers hot bursts of air, leaving "pockets" of cool air.
Is a heat pump as efficient for cooling as a central air conditioner? Yes. A heat pump and a central air conditioner with equal SEER ratings cool with the same efficiency.
What maintenance would I have to perform on an add-on heat pump? It is as easy to maintain as a central air conditioner. Change filters regularly and keep the outdoor unit free of grass, leaves, shrubbery and other debris. Have it checked annually by a qualified service technician to ensure efficient operation.
Since the heat pump seems similar to an air conditioner and yet runs year-round, will it wear out sooner? No. Heat Pumps are engineered to run year-round, and recent technological advances have greatly improved reliability. The typical life expectancy for an add-on heat pump is 15 years or more, and many models offer a 10-year warranty on the compressor.
Does a heat pump require a new duct system? Rarely. The ductwork required by a heat pump is the same used by most central air conditioning systems.

How a Heat Pump Works

Facts:

• Using electricity as its energy source, heat pumps are used for either the heating or cooling of your home by transferring heat between the inside and the outside.
• In the warmer months, the heat pump acts like an air conditioner, removing heat from the air inside your home and transferring it outside.
• During colder months, the Heat Pump runs like an Air Conditioner in reverse. Heat from outdoor air is extracted and transferred to the insider of your home. Believe it or not, even a 32º Fahrenheit day produces enough heat to warm a home via a heat pump.

Benefits:

• Year-round, energy-efficient indoor comfort for moderate climates -A central heat pump helps maintain comfortable temperatures inside your home and reduces humidity levels year-round. Homes located in regions with severely cold temperatures may either require supplemental heating or be better served with an air conditioner/furnace combination.
• Cleaner air - As your heat pump system draws air out of various rooms in the house through return air ducts, the air is pulled through an air filter, which removes airborne particles such as dust and lint. High efficient filters may remove microscopic pollutants, as well. The filtered air is then routed to air supply ductwork that carries it back to rooms. Whenever the air conditioner is running, this cycle repeats continually, constantly filtering and cleaning the air in your home.
• Quieter operation - Because the compressor bearing unit of the typical central heat pump system is located outside the home, the indoor noise level from its operation is much lower than that of a free-standing air conditioning unit.

How a Furnace Works

Facts:

• A furnace works to keep a home warm in the winter and plays a critical part in the operation of an air conditioning system.
• Furnaces produce heat through the Burning of natural or propane (LP) gas in the furnace's burner. The heat produced from this process then passes through a heat exchanger. Air from your home's return air ducts is blown over the heat exchanger, thus warming the air.
• The furnace's blower then blows the warmed air into the ductwork, which carries the warmed air throughout the home.
• During warmer months, the blower inside a furnace continues to circulate return air throughout the home--only this time, being blown over the indoor coil portion of the home’s split-system air conditioning system has cooled the return air. The evaporator coil is typically installed downstrean of the furnace.

Benefits:

• Indoor warmth any time it is required.
• Its AFUE--or Annual Fuel Utilization Efficiency can determine energy efficiency -The efficiency of a furnace. The minimum efficiency level for furnaces currently manufactured in the U.S. is 80% AFUE. A rating of "80% AFUE" means that for every dollar you spend heating your home; 80 cents are used for heating your home and 20 cents go up the chimney to heat the outdoors. Compared to many of the 60% AFUE furnaces in older homes, 80% AFUE furnaces are a significant improvement. However, for the best in energy efficiency, you may wish to consider a 95% AFUE furnace, such as Factory Furnace Outlet’s line of 95% AFUE Furnaces.
• Cleaner air - As your HVAC system draws air out of various rooms in the house through return air ducts, the air is pulled through an air filter, which removes airborne particles such as dust and lint. High efficient filters may remove microscopic pollutants, as well. The filtered air is then routed to air supply ductwork that carries it back to rooms. Whenever the HVAC system is running, this cycle repeats continually, constantly filtering and cleaning the air in your home.

0. This cleaning process improves with the installation of a variable-speed furnace. Variable-speed furnaces use variable-speed blowers, which shift between several speeds. These furnaces will run longer at a low speed, which causes them to filter the indoor air more frequently.
0. And remember - because the furnace plays an important role in the operation of the air conditioner, its variable-speed blower helps maintain both a consistent indoor temperature and improved air quality year-round.

How a Package Unit Works

Facts:

• Package units are unique, all-in-one systems that supply both cooling and heating equipment in one "package." These units sit on the ground or rooftop outside of your home or business.
• Package units come in three forms:

• Packaged heat pumps offer heating and cooling using heat pump technology.
• Packaged air conditioners cool your home and can heat it as well, using electrical strip heat.
• Packaged gas-electric units offer all-in-one air conditioning and natural gas-powered furnace performance.

Benefits:

• Space efficiency - Unlike split-system units, all components of a complete heating and cooling system are contained in one location, making package units ideal for situations in which indoor space is limited.
• Energy-efficient heating and cooling performance - All Factory Furnace Outlet package units offer 13 SEER or higher cooling performance. Our package gas/electric units offer 80% AFUE heating performance, as well.

How an AC Works

Facts:

• The typical central air conditioning system is a split system, with an outdoor air conditioning, or "compressor unit" and an indoor coil, which is usually installed on top of the furnace or in an air handler, in the home.
• Using electricity as its power source, the compressor pumps refrigerant through the system to gather heat and moisture from indoors and remove it from the home.
• Heat and moisture are removed from the home when warm air from inside the home is blown over the cooled indoor coil. The heat in the air transfers to the coil, thereby "cooling" the air.
• The heat that has transferred to the coil is then "pumped" to the exterior of the home, while the cooled air is pumped back inside, helping to maintain a comfortable indoor temperature.
• Central air conditioning can also be provided through a package unit or a heat pump.

Benefits:

• Indoor comfort during warm weather - Central air conditioning helps keep your home comfortable and reduces humidity levels.
• Cleaner air - As your central air conditioning system draws air out of various rooms in the house through return air ducts, the air is pulled through an air filter, which removes airborne particles such as dust and lint. High efficient filters may remove microscopic pollutants, as well. The filtered air is then routed to air supply ductwork that carries it back to rooms.
• Quieter operation - Because the compressor unit is located outside the home, the indoor noise level from its operation is much lower than that of a freestanding air conditioning unit.

Call us and ask us about replacing or parts for your Heat Pump or Air Conditioner

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South Eastern Carolinas Graph from Progress Energy