ASHRAE Terminology

the heating load for the entire one-year simulation period (e.g., for hourly simulation programs, this is the sum of the hourly heating loads for the one-year simulation period).

an operating mode that occurs during either the cooling season or the heating season when the appliance operates to meet a water heating load along with a space conditioning load. With respect to seasonal performance calculations, this mode occurs when both a water heating load and a space conditioning load occurs simultaneously.

the seasonal coefficient of performance of the combined appliance when used to meet both the space-cooling and domestic water-heating loads that occur during the space-cooling season. The quantity is dimensionless.

(1) adjustment of the fuel rate and air/fuel mixture ratio in response to heating load and flue gas air condition over the full range of the burner capacity from some preset minimum to 100%. (2) device or series of devices that control the flow of fuel and combustion air in the desired ratio to provide efficient combustion.

heating rate required to replace heat loss from the space being controlled.

(1) ratio of the heating building load to the steady-state heating load. (2) ratio of the total heating of a complete cycle for a specified period, consisting of an on time and off time, to the steady-state heating done over the same period at constant ambient conditions.

heating load factor

heating load for a given hour.

ratio of actual mean load to a maximum load or maximum production capacity in a given period. See electric power load factor, cooling load factor, heating load factor.

an operating mode that occurs during space cooling when either the refrigerant-to-water heat exchanger water pump has automatically cycled off or the rate of heat transfer to the domestic water has become negligible. With respect to seasonal performance calculations, this mode occurs when the water-heating load is satisfied but a space cooling load remains.

an operating mode that occurs during space heating when either the refrigerant-to-water heat exchanger water pump has automatically cycled off or the rate of heat transfer to the domestic water has become negligible. With respect to seasonal performance calculations, this mode occurs when the water-heating load is satisfied but a space heating load remains.

a modulating control that cycles a burner between the reduced input rate and OFF if the heating load is light. If a higher heating load is encountered that cannot be met with the reduced input rate, the control goes into a modulating mode where it either gradually or incrementally increases the input rate to meet the higher heating load. If, at that point, a lower heating load is encountered, the control either gradually or incrementally decreases to the reduced input rate.

an hour in which one or more zones is outside of the thermostat set point plus or minus one half of the temperature control throttling range. Any hour with one or more zones with an unmet cooling load or unmet heating load is defined as an unmet load hour.