Heat system size requirements?

In air conditioning systems, chilled water is distributed to heat exchangers, or coils, in air handling units, and used water is returned to the chiller. These cooling coils transfer sensible and latent heat from the air to the chilled water, thus cooling and usually dehumidifying the air stream. A typical chiller for air conditioning applications is rated between 15 to 1500 tons (180,000 to 18,000,000 BTU/h or 53 to 3,500 kW) in cooling capacity.