Part J5 Air-Conditioning and Ventilation Systems

See comments for Deemed-to-Satisfy Provisions of .

generally contains minimum energy efficiency requirements for the major energy consuming components of heating, ventilation and air-conditioning systems (HVAC) used in buildings.

Class 8 electricity network substations are exempted from . These substations commonly operate mechanical ventilation or air-conditioning 24 hours a day to serve high voltage equipment, so manual override or specific design features for energy efficiency could be hazardous. See definition of "air-conditioning" in .

is about a system that provides air-conditioning.

It should be noted that the BCA cannot mandate operational or administrative matters such as the set point for temperature control devices, nor would it be practical to do so. It can only require that temperature control devices be installed.

Note that is about air-conditioning units and systems so the floor area measured would only be that for the space served by that air-conditioning unit or system and not include non-conditioned corridors, toilets, plant rooms and the like.

Control—

is about the control requirements for air-conditioning systems so that the consumption of energy is limited.

requires controls to deactivate the air-conditioning system when the area is not occupied and is intended to only apply where the building or part of a building served by the air-conditioning system is unoccupied. For example, if an air-conditioning system serves a whole building, it is only required to be capable of being inactivated when the whole building is unoccupied. Similarly, if an air-conditioning system only serves a single floor of a building, the system must be capable of being inactivated when that part of the building is unoccupied. It is likely this clause will require the operational arrangements to be designed on logical building areas and segments.

outlines that when one space has different thermal characteristics to another space, and both are conditioned by the same air-conditioner, it is necessary to provide separate temperature control devices. A suitable location of the temperature control devices may be in the ductwork supplying the different spaces or the air volume dampers.

For example, consider the differing thermal characteristics between a south and east facing room due to the differing solar gains received. If the temperature sensor is in the east facing room it may activate a higher level of cooling than the south facing room may require. This may result in the south facing room being cooler than desired. An additional temperature control device will allow separate control of the space, facilitating reduced energy use.

requires the temperature control of the air-conditioning system not depend on mixing heated and cooled air streams that have been actively conditioned by the plant. This requirement allows the air-conditioning system to use no more energy than is necessary.

contains restrictions on reheating the supply air. These requirements are intended to encourage the grouping of areas with similar loads (heating and cooling demand), rather than sub-cooling all the supply air and reheating excessively to achieve the desired temperature.

outlines that where a separate temperature control device is provided to reheat the air, then at the full supply air rate for the space, it must not increase the supply air temperature by more than 7.5 K, as there are more cost effective solutions. The 7.5 K limit on temperature rise allows for some trim heating of cold air supply but within reasonable limits.

outlines that the allowable temperature rise can be determined by using an inverse relationship between allowable temperature rise and supply air rate. If, during the reheating, the supply air rate is also reduced then the temperature rise can be proportionally increased above 7.5 K at the same rate that the supply air rate has been reduced. For example, the reheat temperature could be increased to 10 K when the supply air rate is reduced by 25% or increased to 15 K if the supply air rate is reduced by 50%.

requires outdoor air economy cycles to be provided where they can cost-effectively provide free cooling, however an area needing humidity control for process applications is exempt. Outdoor air economy cycles are not considered effective in climate zone 1 and less effective in climate zones 2 and 3. Hence no consideration is given to outdoor cycles in climate zone 1, while by comparison higher allowances are provided for climate zones 2 and 3 when compared to climate zones 4, 5, 6, 7 or 8.

In this clause, the air-conditioning system capacity means the capacity of each air-conditioner serving a space, not the combination of all the units serving a space because an outdoor air economy cycle is cost effective only in a larger unit.

Outdoor air economy cycles can be cost effective particularly in a building such as a Class 6 restaurant or café with a low occupancy. However, there may be situations where the outdoor air required by may be so great that an outdoor air economy cycle would admit only a small additional amount of outdoor air. The added cost of dampers and controls may not be justified for energy savings returned, so a performance based solution may be more appropriate in these circumstances.

An exemption is granted to applications that require humidity control for a specific process related application within the building. It is considered the additional cost and energy use of humidification or activation of a dehumidification plant offsets any benefit of free cooling from outdoor air economy cycle. These applications may include, but are not limited to, a frozen food section of a supermarket, a laboratory or a paper manufacturer's factory.

requires the water flow through major items such as boilers and chillers to be stopped when the item is not needed, usually by an automatic valve. This will reduce the amount of water being circulated and the pump energy needed, as well as thermal loss through the additional components like piping. This requirement is intended to reduce pump energy to its minimum level.

outlines that a variable speed fan must be used when the supply air quantity is capable of being varied. This is because a variable speed fan is a more energy efficient method of reducing energy consumption than throttling the air supply with dampers. A packaged air-conditioning system is exempt.

requires the air-conditioning unit or system to stop when a door to a balcony, patio or courtyard of a sole-occupancy unit of a Class 3 building is open for more than 1 minute. This can be achieved by an electric power micro-switch on the door. The 1 minute timing is to allow for people to open and close the door without the air-conditioning stopping and starting each time. However, if the door is left open for more than 1 minute, it ensures that the air-conditioning does not continue to operate and leak conditioned air.

requires any motorised outside air or return dampers to close when the system is deactivated. It does not require that the dampers be motorised, only that they close if motorised dampers are installed. This requirement is to reduce the infiltration of unconditioned outdoor air via this path when the system is not in use, and so reduce the start-up load when the system is next required to operate.

and require that compliance with must not hinder the smoke hazard management measures required by or the minimum ventilation required by or . This requirement recognises that whilst reducing energy consumption of buildings is important, energy efficiency measures must not impinge upon life safety issues.

Fans—

is a linking clause that requires fans that are part of an air-conditioning system to comply with .

Pumps—

aims to limit the overall energy consumption of the pumps used to circulate water at greater than 2 L/s in an air-conditioning system and the intention is for the pumps to circulate the required amount of water using no more energy than necessary. The maximum pump power values in are included to allow a cost effective balance to be found. Small long pipes use more pump energy than larger shorter pipes for the same water flow while large pipes mean greater capital costs. A holistic or system performance approach is preferred to specifying individual resistance, for components such as coils, heat exchangers, valves and piping, as this approach is less restrictive and permits innovation.

The pump power limits listed in have been developed by modelling typical systems with varying internal loads and allows an increase with larger cooling or heating loads. The cooling or heating load would typically be the design load with an additional safety factor. The maximum pump power requirements recognise a design temperature difference of at least 4ºC for chilled water; a performance based solution could be used where this is not the case. Similarly the pump power limits specified in may not be appropriate for every building design and configuration and it may be more appropriate to use a performance based solution to facilitate the efficient use of energy.

Note that is about pumps supplying chilled water, condenser water or heating water for air-conditioning systems so the floor area measured would only be that for the conditioned spaces served by that air-conditioning system and not include non-conditioned corridors, toilets, plant rooms or the like.

Consideration should be given to the physical space required by the potentially larger piping due to the maximum pump power limits in described above and the piping insulations requirements of .

The system performance approach to regulating pump power means there is no simple correlation between the maximum pump power values specified in , and pump selection. Consequently close communication may be required between the HVAC designer, the pump supplier and the installer to achieve an optimum solution. Additionally, a load profile of the anticipated pump duties may allow for a more holistic solution.

requires the pump speed, where the pump uses more than 3 kW of pump power, to be capable of being lowered to meet a change in duty. This will allow a lowering in pump energy use.

It should be noted that there are instances where higher water flow rates through systems may provide higher efficiencies in connected machinery and it may not be appropriate to vary the pump speed. For example, higher flow rates could result in a lower condenser water temperature in a refrigeration machine which, in turn, would result in lower energy use than any savings in pump power.

Another instance where it may not be appropriate to vary the flow rate is where safety is reliant on the flow rate being held constant, for example, through boilers or water cooled heat pump air-conditioners.

A performance based solution may be more suitable in these instances.

states the requirements for the spray water pumps of a closed circuit cooler or evaporative condenser where part of an air-conditioning system. Any relevant standard can be used to determine the performance and may be part of the tests for closed circuit coolers and evaporative condensers.

Insulation—

is a linking clause and specifies that the ductwork of an air-conditioning system must be sealed and insulated in accordance with .

is a linking clause and requires piping, vessels, heat exchangers and tanks that contain heating and cooling fluids that are part of an air-conditioning system to be insulated to meet the requirements of . Piping, vessels, heat exchangers and tanks that are covered by Minimum Energy Performance Standards (MEPS) are exempt from these requirements.

Space heating—

is a linking clause and specifies standalone heaters used for air-conditioning or heaters used as part of an air-conditioning system such as a boiler, must comply with the requirements of .

Energy efficiency ratios—

outlines that refrigerant chillers used as part of an air-conditioning system, as well as packaged air-conditioning equipment, must have an energy efficiency ratio in accordance with .

Time switches—

specifies the requirements for time switch controlling of power supply to air-conditioning systems. The intent is to reduce unnecessary energy consumption attributable to the system when it is not being used.

Air-conditioning systems and heaters greater than 10 kW must be provided with time switches in accordance with that can activate and de-activate the respective system. The threshold size criterion is based upon where a space is served by a small system, the system is likely to be under the control of the occupants who would determine when the system should operate and therefore could efficiently control the system manually.

grants exemptions for time switches for an air-conditioning system serving a single sole-occupancy unit of a Class 2, 3 or 9c building or a Class 4 part of a building. This exemption recognises that the temperature will be controlled by the occupants as described above. There is also an exemption for a building where air-conditioning is needed for 24 hour occupancy such as a hospital emergency room.

is about a system that provides mechanical ventilation.

It should be noted that the BCA cannot mandate operational or administrative matters such as the pre-programmed times for time switches, nor would it be practical to do so. It can only require that time switches be installed.

Control—

is about the control requirements for mechanical ventilation systems so that the consumption of energy is limited. As outlined in the mechanical ventilation system may be part of an air-conditioning system described in or may be a separate mechanical ventilation system such as a carpark mechanical ventilation system. The requirements do not apply to a mechanical ventilation system that serves only one sole-occupancy unit of a Class 2 building or Class 4 part of a building.

is intended to only apply when the building or part of a building served by the mechanical ventilation system is unoccupied. For example, if a mechanical ventilation system serves a whole building it is only required to be capable of being deactivated when the whole building is unoccupied. Similarly, if a mechanical ventilation system only serves a single floor of a building, the system must be capable of being deactivated when that part of the building is unoccupied.

contains specific requirements for when a mechanical ventilation system serves a conditioned space.

requires that the outdoor air requirement of not be exceeded by more than 20% when serving a conditioned space. This value is to provide the designers some flexibility when supplying a series of spaces from one system. Where there is a need for more outdoor air for one space, it may be appropriate that a dedicated system be installed for that space.

requires a mechanical ventilation system where the building or space has a high density of people and consequently a high rate of outdoor air required by , to have facilities to either reclaim energy from the building's exhaust or reduce the outdoor air rate required by . This must be done in proportion to the number of people in the building. This requirement does not apply to mechanical ventilation systems in climate zone 2 as it would not be cost effective in a climate where the outside air is so temperate.

outlines that there are a number of exemptions from the requirements of where additional outside air is provided.

• The first exemption in is for free cooling provided as part of an outside air economy cycle or when additional outside air needs to be introduced to balance process exhausts such as those used in a health-care building or a laboratory.
• exempts situations where additional outdoor air to balance exhaust ventilation is required by . This may occur in areas such as toilets or bathrooms which have high exhaust rates to remove contaminated air. In such situations, an equivalent level of supply air is required to balance the system.
• The final exemption in is for situations where an energy reclaiming system that preconditions all the outside air is used.

is similar to the requirements for air-conditioning systems in , in that and require that compliance with must not hinder the smoke hazard management measures required by or the minimum ventilation required by and . This requirement recognises that whilst reducing the energy consumption of buildings is important, energy efficiency measures must not impinge upon life safety issues.

Fans—

is a linking clause that requires mechanical ventilation system fans covered by to comply with .

Time switches—

specifies the requirements for time switch controlling of power supply to mechanical ventilation systems. The intent is to reduce unnecessary energy consumption attributable to the system when it is not being used.

Mechanical ventilation systems with an air flow rate of more than 1000 L/s are to be provided with time switches in accordance with that can activate and de-activate the respective system.

grants exemptions for time switches for a mechanical ventilation system serving a single sole-occupancy unit of a Class 2, 3 or 9c building or a Class 4 part of a building.

There is also an exemption in for a building where mechanical ventilation is needed for 24 hour occupancy such as a hospital emergency room or factory.

contains requirements for miscellaneous exhaust systems and examples of these types of systems may include kitchen hoods, laundry hoods and fume hoods. Consideration should also be given to situations where safety is an issue, such as the exhaust from a chemical storage cabinet. Likewise, it may be more appropriate that fume hoods in some situations operate on reduced flow while in other situations operate at full flow. A performance based design may be considered more appropriate in such situations.

Where an air-conditioning or supply air system is installed to provide outside air for ventilation, and this air cannot be relieved from the space by other exhaust ventilation systems or by natural means, then a miscellaneous exhaust system could help to achieve internal air balance. The requirements of this clause are not intended to apply to miscellaneous exhaust systems in these circumstances.

requires a miscellaneous exhaust system with an air-flow rate of more than 1000 L/s that is associated with equipment with a variable demand, to be capable of stopping the motor when not needed and have a variable speed fan or similar to minimise the exhausting of conditioned air so as to reduce energy consumption.

contains an exemption to the requirements of . The requirements do not apply to a miscellaneous exhaust system serving a sole-occupancy unit in a Class 2, 3 or 9c building, or a Class 4 part of a building.

contains an exemption for situations where the exhaust system must balance the intake of outside air required for ventilation. The exemption recognises that the required minimum ventilation rates take precedence over energy efficiency measures.