A series of sensors and relays that monitor and control the functions of a heating and cooling system.
Glossary of Terms
A refrigerant metering device that maintains a constant evaporator temperature by monitoring suction vapor superheat. Also called a thermal expansion valve.
A unit of measurement used for determining cooling capacity. One ton is the equivalent of 12,000 BTUs per hour.
Twostage heating and cooling is considered to be more efficient, because it operates at low speed most of the time. However, on days when more heating or air conditioning is required, it switches to the next stage for maximum comfort.
The factor representing resistance to heat flow of various building materials.
A furnace in which air is drawn in through the sides or bottom and discharged out the top.
A pressure below atmospheric pressure. A perfect vacuum is 30 inches Mercury (periodic symbol "Hg").
The unit of measure used to describe a difference in electrical potential. Abbreviated by the symbol "v".
The force that pushes electrical current along wires and cables.
The unit of electrical power equal to the flow of one amp at a potential difference of one volt.
A thermometer whose bulb is covered with a piece of watersoaked cloth. The lowering of temperature that results from the evaporation of water around the bulb indicates the air's relative humidity.
A method of dividing a home into different comfort zones so each zone can be independently controlled depending on use and need; an air conditioning system capable of maintaining varying conditions for various rooms or zones.