J5.3 Mechanical ventilation system control

(a) General — A mechanical ventilation system, including one that is part of an air-conditioning system, except where the mechanical system serves only one sole-occupancy unit in a Class 2 building or serves only a Class 4 part of a building, must—
[It is applicable for mechanical ventilation which may be part of an air-conditioning system or a separate system such as a car park mechanical ventilation system.]

(i) be capable of being deactivated when the building or part of the building served by that system is not occupied; and
[If the mechanical ventilation system only serves a single floor, when that floor is unoccupied, then it must be capable of being stopped.]

(ii) when serving a conditioned space, except in periods when evaporative cooling is being used—

(A) where specified in Table J5.3, have—
[Where it is specified in Table J5.3; either modulating control or energy reclaiming system to be installed.]

(aa) an energy reclaiming system that preconditions outdoor air at a minimum sensible heat transfer effectiveness of 60%; or
(bb) demand control ventilation in accordance with AS 1668.2 if appropriate to the application; and

(B) not exceed the minimum outdoor air quantity required by Part F4 by more than 20%, except where—
[It is with an exception for evaporative air-conditioning and the criteria below] 

(aa) additional unconditioned outdoor air is supplied for free cooling; or
(bb) additional mechanical ventilation is needed to balance the required exhaust or process exhaust; or
(cc) an energy reclaiming system preconditions all the outdoor air; and

 (iii) for an airflow of more than 1000 L/s, have a variable speed fan unless the downstream airflow is required by Part F4 to be constant.
[It is prescribed where possible that larger mechanical ventilation systems have a variable speed fan.]