Appendix C: Example calculation of the ventilation requirements of a gas-fired appliance

(SEE DIAGRAM 32)

C1 An open-flued boiler with a rated input  of 15kW (net) is installed in an appliance compartment such as a boiler room, which is ventilated directly to the outside. The design of the boiler is such that it requires cooling air in these circumstances.

C2 The cooling air is exhausted via vent D, which has an area:

Equation C2

Equation C2

C3 Vent E allows the cooling air to enter, as well as admitting the air needed for combustion and the safe operation of the flue. It has an area:

Equation C3

Equation C3

C4 The ventilation areas in cm² can be found by dividing the results given above in mm² by 100.