Guide for selecting kitchen fans

1 Guide for selecting kitchen fans Overview This Guide is based on rule of thumb concepts as an aid to fan selection for kitchen hood extraction applications. This should not replace professional advice in the design and specification of complex systems. Australian Standards stipulate a minimum requirement, It is recommended that designers check that this meets their clients requirements. Pacific hvac Engineering staff make calculations based on the AS/NZS. 1668:2002 Standard, and can assist with special applications that fall outside this Standard. Pacific hvac Engineering also has an extensive range of fans for the supply of make-up air and manual or automatic fan controllers. We can also assist in the provision of temperature and pressure controlled fans for use in advanced systems. Calculating air requirements Calculate the required airflow for the Hood using the following formulas.

2 These are derived from Standard AS/NZS1668:2 2002. This is a Guide only. First determine the Hood Process Type. Note, if a hood serves equipment of more than one process type then the highest rated process type shall be applied Process types: Abbreviated from AS1668: 2 2002. Type Grease Typical Equipment 1 None Non Grease producing equipment. 2 Low Griddles, Ranges, Conventional Fryers, Steam Kettles, Gas Ovens 3 High Electric Deep Fat Fryers, Grooved Griddles, Hot Tops and Hot Top Ranges. 4 High Countertop BBQ, Gas Deep Fat Fryers 5 High Woks, Salamanders, any open flame solid fuel cooking. For Corner, Sidewall and Island Canopies For Low Sidewall (Back-shelf) Canopies Type Formula Type Formula 1&2 Q = (190 x P x H) / 1000 1&2 Q = (400 x L) / 1000. 3 Q = (250 x P x H) / 1000 3 Q = (600 x L) / 1000. 4&5 Q = (375 x P x H) / 1000 4&5 Q = (800 x L) / 1000. Use the appropriate formula above, with the process type selected from top table.

3 Q. Q = Required Air qty in m3s-1. P = Inside Perimeter of hood in Metres (exposed sides). H = Height of Hood above cooking appliance L = Length of Hood P. L. H. Pacific hvac Engineering 2015 Tel. Australia 1300 733 833 NZ 0800 100 326. Guide to calculating system resistance for Exhaust Canopy Systems The table below lists approximate static pressure drops for different fittings at a design velocity of 8ms to 12ms. The higher the duct velocity, the more suspended particles such as grease are carried through and ejected from the duct. Lower velocities will increase the cleaning frequency required. This is a Guide designed to enable fans to be selected, which will perform effectively. The data is a combination of ASHRAE and field experience results. Historically, many fans have been requested which are not appropriately sized to meet the airflow requirements of the AS1668 Standard.

4 By meeting the Standard you help to ensure that your customer is able to fully utilise your canopy product, this reduces the incidence of call backs to address airflow related issues. Schedule of fittings and approximate Static Pressure loss. Fitting 8ms Static 10ms Static 12ms Static Internal Hood Losses (if Hood is >3:1 Length/width Ratio) 19 30 43. Duct Connection to Hood 19 30 43. 90 Deg Bend (Mitre) 46 72 103. 90 Deg Bend (Radius) 40 63 90. Expansions and Contractions 6 10 15. Y' Piece 44 70 100. Outlet Chinamans Hat' 57 90 130. Outlet Horizontal Cut-off no guard 32 51 73. Outlet Horizontal Cut-off with finger guard 50 78 110. Steel Ducting (per metre) 2 3. Spiral Ducting (per metre) 3 4 5. Standard Overall Pressure Drops. Fitting Static Low-Loss Filters (Set) 35Pa Standard Filters (Set) 50Pa Calculating system velocities and Duct Sizing for Exhaust Canopy Systems Canopy systems should run at a minimum of 8ms-1.

5 While from a particle ejection point of view it is often better to run at higher velocities, the extra energy and higher fan power requirements often make this undesirable. It should also be noted that noise generated by duct turbulence will increase with the velocity. Duct velocity is a function of the volume flow through the duct, and the area of the duct. System Velocities and Duct Sizing Volume (m3s-1) = Velocity (ms-1) x Area (m2) therefore Area= Volume / Velocity If you require 2000 l/s for the Hood and a Velocity of 8 metres per second, then Area = 2m3s-1/8ms-1 = To convert this area into an equivalent round duct diameter, divide by Pi, find the Square root of the answer and multiply by 2. To get an equivalent Square size, take the square root of the area. Round Duct diameter = / = SQRT = x 2 = .564m2 Square Duct dimension = SQRT = 500mm x 500mm Pacific hvac Engineering 2015 Tel.

6 Australia 1300 733 833 NZ 0800 100 326. Guide for selecting kitchen fans selecting fans Whatever the application, airflow and pressure required, Pacific hvac . Engineering offers a full range of fans , controllers and accessories to suit and complete your kitchen exhaust system. From all metal construction roof mounted centrifugal and axial fans to Inline adjustable pitch axial and backward curved centrifugals, our fully tested and engineered fans offer optimal performance with quiet operation and ease of installation and maintenance. AX Roof Mounted kitchen Canopy fans Range Code Type Flows to: m3/s Pressures: Sound: VD Axial 16 Med/Low Med KMV Centrifugal 4 High/Med Low Inline fans for Canopies and supply air systems. Range Code Type Flows to: m3/s Pressures: Sound: CS FEF Axial Low Low AX Axial Low/Med/High Med ICQ Centrifugal High/Med Low Roof Mounted Supply Air fans Range Code Type Flows to: m3/s Pressures: Sound: CS Centrifugal High/Med Low VD.

7 selecting Speed Controls There are many speed control options available with features and benefits to suit particular applications. Pacific hvac Engineering is able to provide job specific advice taking into account site and client requirements. The following tables provide a general Guide to selecting speed controls. Single Phase-Electronic Speed Controllers For Against Comments Low Cost Should not control fans below 60% of Generally good for use with small full speed. Energy inefficient. Can fans below Not suitable KMV create motor hum' at low speeds for foot or flange mount motors. Single Phase-Transformer Speed Controllers For Against Comments Very quiet fan operation, more Cost The best speed control to use efficient than electronic controllers. with single phase fans . Can be used with external rotor motors up to 2kW. Three Phase-Transformer Speed Controllers For Against Comments ICQ Very quiet fan operation.

8 Cost and size Easy, five step speed control for external rotor motors Three and Single Phase-Variable Speed Drive For Against Comments Very quiet fan operation , wide Complexity The best way to control three speed range, control inputs and phase fans . signals. Note: It is not recommended to speed control conventional single-phase motors with triac type controllers due to heat build up and noise. Pacific hvac Engineering 2015 Tel. Australia 1300 733 833 NZ 0800 100 326.