Room heat load calculations
Calculate the area in square feet of the space to be cooled, and multiply by 31.25
Area BTU = length (ft.) x width (ft.) x 31.25
Calculate the heat gain through the windows. If the windows don’t have shading multiply the result by 1.4.
North window BTU = Area of North facing windows (m. sq.) x 164
If no shading, North window BTU = North window BTU x 1.4
South window BTU = Area of South facing windows (m. sq.) x 868
If no shading, South window BTU = South window BTU x 1.4
Add the results together.
Total window BTU = North window + South window
Calculate the heat generated by occupants, allow 600 BTU per person.
Occupant BTU = number of people x 600
Calculate the heat generated by each item of machinery – copiers, computers, ovens etc. Find the power in watts for each item, add them together and multiply by 3.4
Equipment BTU = total equipment watts x 3.4
Calculate the heat generated by lighting. Find the total wattage for all lighting and multiply by 4.25
Lighting BTU = total lighting watts x 4.25
Add the above together to find the total heat load.
Total heat load BTU = Area BTU + Total Window BTU + Occupant BTU + Equipment BTU + Lighting BTU
Divide the heat load by the cooling capacity of the air conditioning unit in BTU, to determine how many air conditioners are needed.
Number of a/c units required = Total heat load BTU / Cooling capacity BTU