Air conditioning system

An air conditioning system comprising an air conditioner that implements at least a heating operation and a ventilator including an exhaust fan to exhaust indoor air, an air supply fan to introduce outdoor air, and a total heat exchanger to exchange heat between the indoor air and the outdoor air, wherein

• during heating operation, the air conditioner implements a temperature controlling operation of controlling a room temperature and at least one type of operation not intended for temperature control that is not to control the room temperature, the operation not intended for temperature control generating a heating load,
• when the air conditioner implements the temperature controlling operation, the ventilator performs ventilation in a normal ventilation mode where a ventilation amount is set at a certain ventilation amount or more,
• when the air conditioner implements the operation not intended for temperature control, the ventilator performs ventilation in a ventilation suppressed mode where the number of rotations of the exhaust fan is made greater than that of the air supply fan to place indoor space in a negative pressure and ventilation is performed at an amount smaller than the certain ventilation amount or ventilation is stopped, and
• in the ventilation suppressed mode, the amount of ventilation by the ventilator is set to be smaller in response to a greater heating load that is increased by ventilation performed during the operation not intended for temperature control.