NCC 2016 Volume One
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Specification J5.2a Fans

Specification J5.2a Fans

1. Scope

This Specification contains the requirements for fans used as part of an air-conditioning system or a mechanical ventilation system.

Intent

To clarify that provides the requirements for air-conditioning fans covered by and mechanical ventilation system fans covered by .

2. Application

(a)

This Specification does not apply to—

(i)

fans in unducted air-conditioning systems with a supply air capacity of less than 1000 L/s; or

(ii)

the power for a fan in an energy reclaiming system that preconditions outside air; or

(iii)

the power for process related components.

(b)

Compliance with this Specification must not adversely affect—

(i)

smoke hazard management measures required by Part E2; and

(ii)

ventilation required by Part E3 and Part F4.

Intent

To clarify the application of the Specification.

outlines that the requirements of this Specification do not apply to fans in non-ducted air-conditioning systems with a supply air capacity of less than 1000 L/s, the power for a fan in an energy reclaiming system that preconditions outdoor air nor to the power for process related components such as high particulate air filters. In situations where the process related components do not have a dedicated fan, it may be appropriate that the calculations are undertaken by a suitably qualified person.

specifies that compliance with this Specification 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.

3. Air-conditioning system fans

(a)

An air-conditioning system must be designed so that the fan motor power of—

(i)

the supply and return air fans as a combined total is in accordance with Table 3a; and

(ii)

the fan in a cooling tower, closed circuit cooler or an evaporative condenser is in accordance with Table 3b; and

(iii)

the fan in an air-cooled condenser does not use more than 42 W of fan motor power for each kW of heat rejected from the refrigerant, when determined in accordance with AHRI 460.

(b)

The requirements of (a)(iii) do not apply to the fan of an air-cooled condenser that is part of—

(i)

a refrigerant chiller in an air-conditioning system that complies with the energy efficiency ratios in Specification J5.2e; or

(ii)

packaged air-conditioning equipment that complies with the energy efficiency ratios in Specification J5.2e.

Table 3a MAXIMUM FAN MOTOR POWER – SUPPLY AND RETURN AIR FANS

Air-conditioning sensible heat load

(W/m2 of the floor area of the conditioned space)

 Maximum fan motor power (W/m2 of the floor area of the conditioned space)
For an air-conditioning system serving not more than 500 m2 For an air-conditioning system serving more than 500 m2
Up to 100 5.3 8.3
101 to 150 9.5 13.5
151 to 200 13.7 18.3
201 to 300 22.2 28.0
301 to 400 30.7 37.0
More than 400 See Note

Note: Where the air-conditioning sensible heat load is more than 400 W/m2, the maximum fan motor power must be determined—

  1. in a building of not more than 500 m2floor area, using 0.09 W of fan motor power for each Watt of air-conditioning sensible heat load; and
  2. in a building of more than 500 m2floor area, using 0.12 W of fan motor power for each Watt of air-conditioning sensible heat load.

Table 3b MAXIMUM FAN MOTOR POWER – COOLING TOWER, CLOSED CIRCUIT COOLER AND EVAPORATIVE CONDENSERS

Type of fan

 Maximum fan motor power per L/s of cooling fluid circulated Maximum fan motor power per kW of heat rejected
Cooling tower Closed circuit cooler Evaporative condenser
Propeller or axial 310 W 500 W 18 W
Centrifugal 590 W 670 W 22 W

Note: The cooling fluid circulated may be refrigerant, chilled water, brines or glycol mixtures.
Intent

To facilitate the efficient use of energy by fans in an air-conditioning system.

requires the air-conditioning system to be designed so that the total fan motor power of the supply and return air fans is in accordance with . Note that the term fan motor power is defined and describes what is intended. limits the power that air-conditioning fans can consume while balancing ductwork size and additional costs.

A system performance or holistic approach is preferred to specifying the performance of individual components, such as fans, coils, filters, attenuators and ductwork, as it is less restrictive and permits innovation. Smaller ductwork is lower in capital costs, but can result in more fan energy used for the same air flow. Large ductwork is more expensive and may also result in higher upfront building costs, but use less energy and therefore lower running costs over time. The two sets of values for systems serving small and large areas have been developed by modelling typical systems with varying internal loads. The values vary depending upon the internal sensible heat load in the space. The power allowances increase for higher air-conditioning sensible heat loads which are determined as part of the air-conditioning plant assessment calculations. The Australian Institute of Refrigeration, Air-conditioning and Heating (AIRAH) 'Technical Handbook' provides guidance on calculating this sensible heat load. Additional detail is also provided in AIRAH DA09 'Load Estimation'.

Consideration should be given to the physical space required by the potentially larger ductwork due to the maximum fan motor power limits in described above and the ductwork insulation requirements of .

The maximum fan motor power limits specified in may not be appropriate for every building design and configuration and it should be noted that a performance based solution can always be utilised.

outlines that the requirements for a fan that is part of a cooling tower, closed circuit cooler or an evaporative cooler that is part of an air-conditioning system are located in . The maximum fan motor power allowed is dependent on the type of fan used.

The performance of cooling tower fans, closed circuit cooler fans and evaporative condenser fans can be determined using any nationally or internationally accepted standard. For example Cooling Technology Institute's (CTI) standard CTI STD-201RS(13) and Acceptance Testing Code (ATC) ATC-105(00), can be used to determine the performance of cooling tower fans. CTI STD-201RS(13) and ATC-105S(11) can be used for closed circuit cooler fans and ATC-106(11) can be used to determine the performance of evaporative condenser fans.

states the requirements for a self-contained, air-cooled condenser fan motor that is part of an air-conditioning system. The fan motor must not consume more than 42 watts of fan motor power for each kW of heat removed from the refrigerant. The air-cooled condenser fan is used to cool refrigerant from its vapour phase to its liquid phase as part of the refrigeration cycle.

Air-cooled condensers not part of a package air-conditioner or split unit as per the exemptions in and , are typically associated with larger plant installations. The requirements of are also not intended to capture a condenser covered by MEPS.

The air-cooled condenser fan must be determined in accordance with the Air-Conditioning, Heating, and Refrigeration Institute's (AHRI) standard AHRI 460 - Remote mechanical-draft air-cooled refrigerant condensers.

4. Mechanical ventilation system fans

(a)

When the air flow rate of a mechanical ventilation system is more than 1000 L/s, the system must—

(i)

have a fan motor power to air flow rate ratio in accordance with—

(A)

for general mechanical ventilation systems, Table 4a; or

(B)

for carpark mechanical ventilation systems, Table 4b; and

(ii)

for carpark exhaust, when serving a carpark with more than 40 vehicle spaces, have an atmospheric contaminant monitoring system in accordance with AS 1668.2.

(b)

The requirements of (a) do not apply to—

(i)

a mechanical ventilation system that is part of an air-conditioning system; or

(ii)

the power for a miscellaneous exhaust system complying with J5.4; or

(iii)

a sole-occupancy unit in a Class 2 building or a Class 4 part of a building.

Table 4a MAXIMUM FAN MOTOR POWER TO AIR FLOW RATE RATIO – GENERAL MECHANICAL VENTILATION SYSTEMS

Filtration Maximum fan motor power to air flow rate ratio (W/(L/s))
With filters 0.98
Without filters 0.65

Table 4b MAXIMUM FAN MOTOR POWER TO AIR FLOW RATE RATIO – CARPARK MECHANICAL VENTILATION SYSTEMS

Filtration Maximum fan motor power to air flow rate ratio (W/(L/s))
Air flow rate (L/s)
1,000 to less than 5,000 5,000 to 50,000 More than 50,000
With filters 0.78 1.12 1.81
Without filters 0.52 0.74 1.2
Intent

To facilitate the efficient use of energy by fans in a mechanical ventilation system.

defines that the maximum allowable fan motor power to air flow ratio in a general mechanical ventilation system over 1000 L/s must be in accordance with . This clause is about selecting an efficient fan irrespective of the system pressure, but does so based on system performance. The fan motor power to air flow rate ratio is found by dividing the fan motor power (W) by the total flow rate (L/s) and there are differing maximum allowances based on whether or not filters are used. Note that fan motor power is a defined term that describes what is intended. The system flow rate and resistance is determined at the time of design. It should also be noted that motor efficiency performance is controlled by MEPS.

is about mechanical ventilation systems that are used for carparks and again only applies to systems where the air flow rate is more than 1000 L/s. The maximum allowable fan motor power (W) to total air flow rate (L/s) ratios are contained in . The maximum allowances vary based on the air flow rate (L/s) and whether the system has filters installed.

requires a monitoring system to control the mechanical ventilation system in a carpark of over 40 vehicle spaces. AS 1668.2 has provision for reducing the ventilation rate if an atmospheric contaminant monitoring system is installed.

Similar to the maximum fan motor power levels specified for air-conditioning fans in , the maximum fan motor power limits specified for mechanical ventilation systems may not be appropriate for every building design and configuration. A performance based solution can be used to demonstrate compliance.

outlines exemptions to the requirements of in that the requirements of do not apply to a mechanical ventilation system that is part of an air-conditioning system, a miscellaneous exhaust system complying with , or a system serving a sole-occupancy unit in a Class 2 building or a Class 4 part of a building.