Contamination

Any foreign object or substance not normally found in a specific location.

Convection

A heat transfer process involving motion in a fluid (such as air) caused by the difference in density of the fluid and the action of gravity. Convection affects heat transfer from the glass surface to room air, and between two panes of glass.

Cooling

The transfer of energy from a body of solid, liquid or gas by the existence of a temperature gradient from that body to its surroundings which are at a lower temperature, and may also be solid, liquid or gas. This process is the opposite of heating.

COP

The Coefficient of Performance is a ratio used in rating the heating efficiency of heat pumps.  It is determined by dividing the total heating capacity (excluding supplementary resistance heat) by the total electric input.

Corrosion

The decay and loss of a metal due to a chemical reaction between the metal and its environment. It is a transformation process in which the metal passes from its elemental form to a combined (or compound) form.

Cost Of Kw

The cost of electricity charged by the electric and is typically $0.04 to $0.15 per kilowatt depending on geographic location.

CPLV - Calculated Part Load Value

The calculated Kw/Ton derived from the effect of part load and entering condenser water temperature on the chiller when compared to full load design.

Crawlspace

A shallow space in a building, usually under the floor, which provides access to pipes, wires and other equipment.

CRF

Condensation Resistance Factor. An indication of a window's ability to resist condensation. The higher the CRF, the less likely condensation is to occur. Based on AAMA standard.

Cross Ventilation

Air enters on one side of a room and leaves on a different side of the same room. Airflow between the entry and exit provides ventilation. Also used for flow between rooms, where the inlet is in one room and the outlet is in another.

Cycle

One complete execution of a repeatable process. In basic heating operation, a cycle comprises one on period and one off period in a two-position control system.

Cycling

A periodic change in the controlled variable from one value to another. Uncontrolled cycling is called hunting.

Damper

Flat plate that opens and closes to control amount of air flowing through a heating duct, exhaust vent, flue, or chimney.  A movable plate that controls airflow through a ductwork system. Dampers are used to direct air to the areas of the home that need it most.   A type of "valve" used in ductwork that opens or closes to control airflow. Used in zoning to control the amount of warm or cold air entering certain areas of your home.

Dampproofing

To coat a surface to prevent the passage of moisture.

Dangerous Or Adverse Situations

Situations which pose a threat of injury to the installer/technician, and those situations which require the use of special protective clothing or safety equipment.

Day Economization

A control scheme which permits heating or cooling plant to be turned off completely if the anticipated fall or rise in internal temperature does not exceed pre-selected limits within a period, usually 1 hour.

DC

Direct Current electricity This type of electricity (as opposed to Alternating Current, or AC) flows in one direction only, without reversing polarity.

Dead Band

The change of input for which there is no discernible change in output. A dead band may be imposed on an output device e.g. An actuator to avoid continuous movement due to small changes in the input signal.

Dead Load

The weight of permanent, stationary construction included in a building.

Deaeration

The act of separating air from a substance.

Decibel (Db)

The unit used for measuring relative loudness of sounds. One decibel is equal to approximate difference of loudness ordinarily detectable by human ear, the range of which is about 130 decibels on scale beginning with one for faintest audible sound.

Deck

The surface installed over the supporting framing members, to which the roofing is applied. Also, an uncovered porch type structure normally constructed with unpainted lumber with a gap between the flooring material.  In HVAC terminology, the air discharge of the hot or cold coil in a duct serving a conditioned space.

Deck (Coil Deck)

The insulated horizontal partition between refrigerated space and evaporator space.

Deficiency

An inadequacy in the structure or one of its components.

Deficient

In functionally deficient condition, needs immediate repair or replacement.

Defrost Circuit(s)

Heat pumps extract heat from the external atmosphere even at very low temperatures is inevitable the external coil freezes with ice. The coil therefore has to be warmed periodically in order to remove the ice this is achieved by running the refrigeration circuit in reverse for a brief period of time. This cycle is referred to as the defrost cycle and therefore unlike a condensing unit (i.e. Cooling only unit) heat pump units form water externally. Therefore, consideration has to be given to the removal of the water formed, by the provision of an external tray or other device.

Defrost Cycle/ Defrost Mode

The refrigerating cycle in which evaporator frost and ice accumulation is melted.

Defrost Timer Device

Is connected into electrical circuit which shuts unit off long enough to permit ice and frost accumulation on evaporator to melt.

Defrosting Evaporator

An evaporator operating at such temperatures that ice and frost on surface melts during off part of operating cycle.