The rate of air change per hour is calculated by using the formula ACH = 60 x CFM/V. In SI units, the calculation formula is expressed as n = 3600 x Q/V, according to the Engineering ToolBox.
Know MoreCFM denotes the cubic feet per minute rating of a fan and is found in a fan?s manual, specification sheet or literature. Since CFM is expressed in minutes rather than hours, it is converted into cubic feet per hour by multiplying the CFM value with 60. Airflow in physics is denoted as Q, and when it is expressed in cubic meters or cubic feet per second, it needs to be multiplied by 3,600.
V denotes the volume of the room in cubic feet or cubic meters and is determined by using a measuring tape. The length, width and height of the room are measured in feet or meters and then multiplied by each other to get the volume.
The term ?air changes per hour,? also abbreviated as ACH or ac/hr, is obtained by dividing airflow per hour with the volume of the room. It is used to describe the number of times air in the room is completely changed within one hour. It is a measure used in ventilation planning and air purifier ratings.
Learn more about Heating & CoolingUse the area of a room to determine the proper air conditioner size estimate, which is measured in British thermal units per hour. A 100- to 150-square-foot room needs a 5,000 BTU per hour unit, while a 400- to 450-square-foot room needs a 10,000 BTU per hour unit.
Full Answer >A 10-ton air conditioning unit is a cooling system capable of removing 120,000 British thermal units of heat per hour from the air in the building to which it is attached. In this system of measurement, 1 ton is equal to 12,000 BTUs of heat extraction per hour.
Full Answer >Zones for air conditioning are determined by calculating the length of time light and heat are received from the sun throughout a house at various parts of the day.
Full Answer >BTU is an abbreviation for British Thermal Unit, which is the international measure of energy. An air conditioner's BTU must be matched to the size of the room for adequate cooling. BTU tables estimate different energy requirements.
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