TechTalk Issue 69
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Transcript of TechTalk Issue 69
December 2010Newsletter Number 69
New Zealand supermarket giant Progressive Enterprises has made a commitment to reduce the companys overall carbon footprint by 40% by 2015, bringing emissions back to 2006 levels.
Progressive, a subsidiary of Australian company Woolworths Limited, owns and operates 152 supermarkets in New Zealand including the Woolworths, Foodtown and Countdown brands. Over the next five years all Woolworths and Foodtown stores will be converted to the Countdown brand.
Fantech NZ is proud to have been associated with the latest new store, Countdown Manukau located in Manukau City, South Auckland.
McAlpine Hussmann Limited was contracted to install the mechanical services. Air Conditioning Sales and Project
Engineer Edlay Hojird said the building had a 10,000sqm (100 x 100m) footprint, with a single level basement car park and ground floor retail area.
Along with all new generation Countdown supermarkets, the Manukau store features sustainable design initiatives such as increased use of natural light and energy efficient building management systems. To curb energy consumption from refrigeration and freezer units, the store has introduced energy efficient refrigeration cabinets with new more environmentally friendly refrigerant gases.
Edlay said the green design philosophy had extended to the basement carpark where 11 JetVent impulse jet fans from Fantech had been installed. The 50N units are controlled by a gas detection system that ensures carbon monoxide, nitrous oxides and fumes from vehicles are controlled and extracted appropriately.
The JetVent fans were selected in conjunction with the Mechanical Consultant, Thurston Consulting. Fantech NZ Technical manager Nigel McQueen said energy efficiency had been a major objective when deciding what fan to use. Our selection was also governed by the design of the support floor, a stressed diaphragm construction which did not incorporate support beams, he said.
The Countdown car park is a semi-open design that has multiple openings in the outer walls. The JetVent system works on well-proven tunnel principles and is able to use these openings to ensure a constant movement of air without the need for ventilation shafts, Nigel said. A computational fluid dynamics (CFD) analysis confirmed the most appropriate location for each of the 11 fans which draw air in via the North side of the car park and push it out via the South side.
Ceiling height is often restricted in a car park, and although the Countdown basement car park is 2.7m high, the designers did not want to clutter it with ductwork typically associated with traditional car park ventilation.
The very low profile housing of the JIU series of JetVent fans makes them ideal for general car park ventilation. Furthermore, because an extensive ductwork system isnot needed, the result is an aesthetically pleasing, clean car park ceiling and reduced installation costs, Nigel said. The entire car parking area appears more spacious, and with the absence of ventilation shafts designers have been able to maximise the number of car park spaces to 319.
Edlay said Fantech had played a major role in the HVAC requirements of the complex. In addition to the carpark fans, Fantech supplied a number of productsfor general ventilation in the Countdown store, mall, retail areas, amenities and toilets.
The JetVent system works on well-proven tunnel principles...
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New Zealand supermarket giant Progressive Enterprises has made a The Countdowwnnnn cacacacarrrr ppark is a semi-open design that has
NZ Supermarket goes green
Thida Kao & Peter Cotterell
Fans are a significant user of energy. The current best data suggests that fans are responsible for anywhere between 8% and 20% of the total worldwide electricity consumption and, of this total, 55% is consumed in the commercial sector. It is no surprise that improving the energy efficiency of fans is considered one of the most cost effective means of greenhouse gas abatement.
To help address the limited uptake of energy efficient fans, regulations are being specifically written for fans and ventilation systems.
The Building Code of Australia (BCA) includes a section on Energy Efficiency called Section J which has recently been updated in BCA 2010. Also, a Minimum Energy Performance Standard (MEPS) for fans used across all industry sectors is currently under investigation. This article will highlight the main points to consider when designing a system to comply with Section J5.2 of BCA 2010.
BCA 2010In 2010 the stringency of energy efficiency measures for fans in the BCA has increased significantly, especially for higher pressure duct systems. The most significant changes have occurred in Clause J5.2 (b) (iii) (A).
Clause J5.2 (b) (iii) (A) states:
When the mechanical ventilation system is provided by means other than an air-conditioning system and the air flow rate is more than 1,000L/s
(A) Have a fan power to airflow rate ratio of 0.5W/(L/s) without filters or 0.75W/(L/s) with filters for a general mechanical ventilation system
This clause applies to ventilation fans that are not part of an air-conditioning system and excludes systems with HEPA filters, and miscellaneous exhaust systems (eg. kitchen exhaust fans or ventilation fans for chemical baths).
The W/(L/s) dictates the amount of motor shaft power (W) allowed for every L/s of airflow delivered by a fan. As an example, if the allowable W/(L/s) is 0.75, and the airflow is 2,000L/s, the allowable motor shaft power would be 0.75 x 2,000 = 1,500W.
As a comparison between BCA2010 and the previous BCA2009 requirements, if we had a fixed pitch, fixed speed fan with a static pressure drop of 350Pa, the power consumption would need to be reduced from 1.15W/(L/s) as shown in Table 1 to the new constant 0.5 W/(L/s) level. In other words we would only be able to consume 43% of the power specified in the previous BCA version.
As shown in table 1, in BCA2009, the Section J5.2 W/(L/s) values increased with pressure drop. That is, the higher the pressure drop the more power could be consumed for the same airflow. By changing the W/(L/s) to a constant value in BCA2010 (ie. 0.5 W/(L/s)) the result is that higher total system pressure drops require fans with higher total efficiencies.
Table 2 shows the minimum fan total efficiencies required to achieve both 0.5W/(L/s) and 0.75W/(L/s) at different total pressure drops. As peak fan total efficiencies are typically in the range of 30%-75%, depending on fan type and size, we can see that BCA2010 will limit the maximum total system pressure drops allowable in installations.
If we look at a specific tested fan example, by examining the power consumed at each point on a sample in-line, backward-curved centrifugal fan performance curve and dividing it by the airflow, we can plot the changing W/(L/s) fora specific fan, as shown in the graph below. By plotting the W/(L/s) curve against the airflow performance curve, we can see that W/(L/s) increases with fan static pressure drop. Therefore the highlighted region to the right of the 0.5 W/(L/s) intercept shows where this fan complies with Clause J5.2 (b) (iii) (A). In this case the fan static pressure drop would not be able to exceed 165Pa in order to comply.
Example of W/(L/s) against airflow for a specific fan.
ConclusionBCA 2010 Section J5.2 will reduce the amount of energy consumed by fans by reducing the allowed total pressure of duct systems. The intention of the BCA therefore is to be more system focussed, although fans will also need to become more efficient. Based on the efficiency of fans available in the marketplace today a good rule of thumb is that duct systems should not exceed a total pressure drop of 300Pa (where filters are not used in a ventilation system). Where filters are part of a ventilation system, the total pressure drop should not exceed 500Pa.
This topic will be continued in the next issue of Tech Talk where the effects on total pressure drop, and methods of rating motor power will be discussed.
Technically SpeakingImplications of Section J5.2 of the BCA 2010 (Part 1)
With Kerry Dumicich
Test fan inside furnace
System Static Pressure Drop (Pa)
Shaft W/(L/s) in BCA2009 for Fixed Pitch / Fixed Speed
200 0.75300 0.95400 1.15500 1.4600 1.6
Fan Total Effi ciency required %
System Total Pressure (Pa)
0.5 W(L/s) 0.75 W/(L/s)
100 20% 13%200 40% 27%300 60% 40%400 80% 53%500 100% 67%600 120% 80%700 140% 93%
01.0 1.2 1.4 1.6 1.8 2.0 2.2
Region < 0.5 W/(L/s)
Air flow (m3/s)
Air flow PerformanceW/(L/s)
Table 1: Fan W(L/s) levels in BCA2009
Table 2 : Fan Total Efficiencies required to achieve W/(L/s) levels
Tip No.9: Selecting a SilencerThe Fantech Selection Program has two methods of selecting a silencer. The most direct way is to click Silencers from the main Fan Selection screen. Alternatively, you can continue from the Acoustic Analysis we performed in the previous issue by clicking the Select Silence button and the program will automatically fill in the required Insertion Loss values.
On the Silencer Selection Details screen, enter the Air Flow where you have the choice of entering a Maximum Pressure Drop to limit your results. For Rectangular Silencers, you must specify the Width and Height; for Circulars, Diameter is essential. If Length is an important factor, you can enter that too. If you havent performed an Acoustic Analysis, you will need