When Cooling is Critical
Part 1: Cooling: Assess Overall Heat Gain to Calculate Loads
Part 2: Rent or Buy Cooling Equipment? Three Considerations
Part 3: Data Centers: Design Principles for Providing Critical Cooling
Part 4: Cooling Equipment: Technician Training
Part 5: Calculating Cooling: Load-Factor Definitions
Calculating Cooling: Load-Factor Definitions
By Thomas A. Westerkamp - July 2009 - HVAC
Once managers have completed the list of data center equipment, they can calculate the actual cooling load the space requires. Below are load-factor definitions needed for this step in the process:
• British thermal units (Btu). Btu measure the amount of heat required to raise the temperature of 1 pound of water 1 degree.
• Ton. One ton of refrigeration — 12,000 Btu per ton — is the amount of heat required to melt 1 ton of ice at 32 degrees. Many rooftop, area and central cooling units are rated in tons.
• Equipment cooling load. Every watt equals 3.41 Btu of cooling load. Managers can calculate the cooling load for each piece of equipment by multiplying either: the number of watts by 3.4 to produce Btu; or volts by amps by 3.4 to produce Btu.
Add up all the units’ Btu to determine the equipment’s total cooling load, and divide the Btu by 12,000 to determine the tons.
