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HVAC Definitions

HVAC Ann Arbor

AFUE - "Annual Fuel Utilization Efficiency". Rating of how much energy a furnace converts to heat. The higher the AFUE, the more efficient a furnace / heating system is.

ARI - "Air Conditioning and Refrigeration Institute", industry organization of HVAC equipment manufacturers which sets standards for testing cooling and heating equipment.

BTU - "British Thermal Unit", measurement of heating or cooling. One BTU is equal to the amount of heating or cooling needed to raise or lower the temperature of one pound of water by one degree (Fahrenheit).

BTUH - measurement of HVAC equipment's ability to heat or cool in BTU's per hour.

CFM - "Cubic Feet (per) Minute", measurement of movement of air through a heating, ventilation or cooling system, (e.g.- an 300 CFM fan will move three hundred cubic feet of air in one minute).

CAPACITY - HVAC capacity is the output produced by the heating or cooling unit and is measured in BTUs per hour.

COMPRESSOR - a pump that increases the pressure of gas.

CONDENSATE - vapor that is turned into a liquid as its temperature is lowered.

CONDENSER 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.

DECIBEL (dB) - a unit of measure of sound.

DUCT / 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.

EER - "Energy Efficiency Ratio"

EFFICIENCY - rating of HVAC equipment comparing how much energy is used and how much heat is produced. A unit rated ar 50% produces only $.50 of heat for each dollar spent.

EVAPORATOR 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

FHR - "First Hour Rating", amount of water (in gallons) a conventional storage tank type hot water heater can deliver in the first hour of use when tank is full.

HEAT EXCHANGER - a device through which heat is transferred to a cold area or surface.

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.

HVAC - "Heating, Ventilating and Air Conditioning"

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


KILOWATT - 1,000 Watts, or "kW."

KWH - "Kilowatt Hour", measurement of watts used per hour.

MULTI SPEED BLOWER MOTOR - A blower motor that has multiple speed options to select from (high, medium, low). These speeds are selected to run during certain stages of the heating and air conditioning system by the furnace installer. If the heating speed is set for low then the furnace will always run at low speed during the heating cycle.


REFRIGERANT - a gas or liquid used in air conditioning systems which condenses under pressure and in the process decreases in temperature. Commonly known refrigerants are "R-22", "R-410A".

  • R-22 common name for HCFC, (hydro-chlorofluorocarbon), a refrigerant gas used in HVAC equipment for nearly 50 years. Recent studies show that HCFC type refrigerants contain chlorine, an ozone-depleting agent and will be phased out of production by January 1, 2010.

  • R-410A - common name for "HFC", (hydro-fluorocarbon) a newer refrigerant gas used in HVAC equipment as it is more environmentally friendly than R-22.

REFRIGERANT LINES - tubing through which a refrigerant gas passes.

SEER - "Seasonal Energy Efficiency Rating". The higher the SEER rating, the more efficient the unit.

SPLIT SYSTEM - an HVAC system which uses indoor and outdoor components to perform heating and cooling.

SRN - "Sound Rating Number", the lower the SRN the quieter a unit is rated.

THERMOSTAT - temperature measuring and control device.

TON - 12,000 BTUs, (see BTU definition).

VARIABLE SPEED BLOWER MOTOR - A motor that is able to run at capacities between 20% and 100% based on pre programmed algorithms in the circuit board of the furnace. This blower motor converts A/C current to D/C current which enables the blower motor to run at a lower cost to operate. The benefits of a variable speed blower motor are, 1/3 of the cost to operate the fan, quieter operation, fan ramps up and down slowly, continuous air supply into the home at lower speeds.

WATT / WATTS - unit of measure of electrical energy.

ZONE - a defined area within a building where heat and cooling are controlled by a thermostat. In building with only one zone, a single thermostat controls temperature throughout the building. HVAC systems with multiple zones can send heat or cooling to a particular room or area.

Customer Center: 3611 Central Street Dexter, MI 48130

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