Glossary of Terms

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Thermidistat: A type of thermostat control that monitors and controls temperature and humidity in a home or business. The thermidistat control monitors both indoor and outdoor temperatures and adjusts the heating and cooling system to maintain desired levels set by the owner. Thermidistats are usually programmable thermostats as well (setback thermostats).

Thermostat: An HVAC control that monitors and controls the temperature for a home’s heating and/or cooling system. The thermostat is usually located on an interior wall.

Thermostatic Expansion Valve: A Thermostatic Expansion Valve (TXV) is a precision device used to meter the flow of liquid refrigerant entering the evaporator coil at a rate that matches the amount of refrigerant being boiled off in the evaporator.

Ton: Unit of measure for determining cooling capacity. One ton equals 12,000 BTU’s.

Two Stage Compressor: A compressor that provides two levels of heating or cooling output for greater temperature control, energy efficiency, and improved indoor comfort. Two stage compressors can either be scroll or reciprocating type compressors.

UL: UL is an objective, non-profit organization that tests and rates electrical products for public safety.

Upflow: A type of furnace or fan coil that draws cool air form the bottom and blows the warmed air out the top into the ductwork. This type of furnace is usually installed in a basement or out-of-the-way closet.

Variable Speed Motor: A motor in a furnace or fan coil that automatically adjusts the flow of warm or cool air for ultimate comfort. Often a variable speed unit is controlled by a thermidistat and is used as an aid in dehumidification.

Ventilator: A system that exchanges stale, recirculated indoor air with fresh, filtered outside air. These units are designed to be a stand-alone system with their own ductwork and controls or can be tied in conjunction to the homes forced air HVAC system. These systems are commonly called Energy Recovery Ventilators, or ERV’s.

Zoning: A method of portioning a home into independently thermostatically controlled areas. Commonly used on boilers and some forced air systems. Utilizes motorized dampers and thermostat controls to regulate the flow of water or air on an HVAC system.