Determining Supplemental Air Conditioning tonnage needs for areas such as IT Rooms, Broadcast Edit Rooms, Control Rooms or General Office Space is determined by the heat loads generated by equipment, people and light required at each location.  The following will help you determine calculating the heating and cooling thermal units (BTU) and how to convert that number into tons.

Electrical vs Heat Load Calculation Summary

Watts= Amps x Volts
1 Amp @120 Volts = 120 Watts
1 Watt of Power = 3.412 BTU

3.412 BTU x Watts = X BTU

1 ton of cooling is 12,000 BTU/hour, not counting people load.

Determining Tonnage

1. Measure the length and width of the room and convert that figure into BTU’s which is determined by multiplying the length and width. The measurement must be in meters, (1 foot equals .3048 meters). Multiply the area by 337 to figure out the area BTU.

Room BTU = Length x Width (in meters) x 337

2. If there are north or south-facing windows in the vicinity, calculate the BTU for each window by measuring the area of each. For north-facing windows, multiply the area by 165. For south-facing windows, multiply the area by 870.

3. Calculate the BTU of the number of people who work in the location. Multiply the occupants by 400 for the BTU.

4. All the equipment in the room needs to be measured for their BTU output. To determine the output, multiply the total wattage for every piece of the equipment by 3.412. Wattage can be found listed on the equipment or the equipment’s instruction manual.

5. Determine the lighting BTU by multiplying total wattage for the lighting by 4.25.

6. Add the figures from steps one through five. The result is your total heat load. Multiply this number by two to determine the amount of cooling required.

7. Convert your heating and cooling load to tons by dividing the BTUs by 12,000. The resulting figure is the HVAC tonnage.