Cooling Calculation

Heat load in watts = S x (Te-Ti) x K

Where:-

S = Square area in m2

Te = External Temperature

Ti = Internal Temperature

K = Thermal coefficient of the room to be conditioned

(Te - Ti) = typically, for the Mediterranean uses 8-10 which is the difference you want to achieve between outside and inside temperature. For tropical climates the standard value is 15.

The K value is determined by the solar gain, the quantity of people and the use of the room. Typically these values are as follows:-

• Owners cabin and guest cabins: K = 20-22
  
• Saloon or dinette with limited window and glass area (sailing yacht or power "open" configuration): K= 28-30
  
• Saloon or dinette with large glass area (power boat - fly-bridge configuration): K=35
  
• Wheelhouse (power boat) with very large glass area: K=40
  

As an example, to air-condition a dinette in a "open" power boat: its area is (3m x 2m) = 6m2; the heat load is then:

• W = 6m2 x 30 (K) x 10 (Te -Ti)= 1,800w
  

This number represents the amount of heat to be extracted by the air-conditioner in order to keep the inside temperature 10 °C below the outside temperature expressed in watts.

As most of the marine air-conditioning industry still works in imperial units the BTU/Hr equivalent is calculated as follows:-

• 1800w x 3,410 = 6,120 BTU/Hr