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flue diltution - 6 Pages
IMPROVED GBDFMK5 TIONFANS Choosing the Correct Size and Type of Fan Where possible there should be at least 2 mtres of flue ducting from the fan to the outlet. To ensure a maximum of 1 % co2 content at the outlet, the volume flow rate of diluted flue gases necessary for a given boiler can be calculated as follows: Flow rate in litres/s = 2.69 x rated input of boiler in kW. Where 2 mtres of discharge ducting is not possible then the calculation is: Flow rate in litres/s = 4.44 x rated input of boiler in kW. The volume flow rate provided by the fan will d訩pend on the static pressure imposed by the size and length of flue ducting and the number of bends, louvres etc. comprising the installation. The performance table below enables slection of the correct dilution fan based on the flow rate requirement and the fans ability to overcome duct System rsistance. (Note if LPG or Butane are being used then the factors above should be increased to 3.23 and 5.33 respectively. Th驨se flue dilution fans must not be used for any other fuels). Performance table at 20°C FAN SIZE Static Pressure (Pascals) Frec Air 10 20 30 40 50 60 70 80 90 100 110 120 130 140 160 180 200 225 250 275 300 325 350 375 GBDF 2 SSDF 2 Volume Litre/s 300 290 280 260 250 240 230 220 190 140 80 40 0 GBDF 3 SSDF 3 Volume Lilre/s 600 580 570 560 540 520 510 500 480 460 440 410 380 320 280 120 40 0 GBDF ■! SSDF 4 Volume Litre/s 1000 985 970 950 935 920 900 880 860 840 815 780 760 740 710 640 520 340 200 80 0 GBDF 5 SSDF .'. Volume Litre/s NOT 3UITA 111 n DNOl USE 1400 1370 1350 1325 1300 1260 1200 1150 1075 975 850 450 200 80 0 GBDF C SSDF 6 Volume Litre/s 1750 1675 1570 1420 1280 1085 850 625 460 1 N( )T SU rtABL DO h OT U NOTE: A MINIMUM DUCT RESISTANCE OF 90 Pa ON THE SIZE 5 AND 180 PA ON THE SIZE 6 IS NECESSARY TO AVOID OVERLOADING MOTOR Typical performance table at 20°C The above calculation should generally be used. However, if ail the following conditions can be met then the typical performance table shown below can be used. (i) Ducts match inlet and outlets of fan. (ii) The louvres on the discharge and fresh air inlets have 50% FREE areas and not less than the minimum sizes shown in the chart below. (iii) The dilution air inlet is on the same face of the building as the discharge. (iv) There are not more than two right angle bends in the System. (v) The flue System is not more than 10 mרtres total length and includes not less than 2 mtres after the fan outlet. FAN SIZE UNITS GBDF 2 GBDF 3 GBDF 4 GBDF 5 GBDF 6 FAN MIN. DUCT MAX. LINE SSDF 2 SSDF 3 SSDF 4 SSDF 5 SSDF 6 SIZE RESISTANCE CURRENT maximum boiler input rating kw 80 160 270 425 650 GBDF 5 90 Pa 2.6 AMPS minimum inlet duct diameter mm 254 305 305 457 457 SSDF 5 minimum inlet louvre size mm 300 x 300 400 x 400 400 x 400 600 x 600 600 x 600 GBDF 6 SSDF 6 180 Pa 2.9 AMPS minimum discharge duct diameter mm 225 275 345 370 457 minimum discharge grille size mm 300x300 400x400 450 x 450 500 x 500 600 x 600 THESE minimum duct rsistances required on mode! sizes 5 and 6 diluted flue gas volume Us 215 430 730 1145 ! 750 total static pressure loss in System pa 70 93 130 I60 180 maximum flue velocity 5.5 7.3 7.9 10.7 10.7 General Installation Advice Each Airflow flue dilution fan is provided with a fresh air inlet on the drive side of the fan. Typically 30-40% of the air passing through the fan enters this inlet which if not ducted to the outside takes fresh air from the boiler room. An ad詩quate supply of fresh air by means of inlet louvres in the boiler room walls must be made available to the boiler to provide air for combustion and ventilation. To ensure this AND provide dilution air to an unducted motor side inlet the following calculation for high and low level grilles should be used. Low level (intake): 1080 cm2 plus 9 cm2 for each kilowatt input in excess of 60 kw rated input. High level (extract): 270 cm2 plus 2.25 cm2 for each kilowatt input in excess of 60 kw rated input. In order to avoid recirculation and therefore build-up of products of the combustion in the System, it is advisable to ensure that the dilution air inlet is at least 2 mtres (6ft) from the discharge. If positioning of discharge and inlet is difficult. it is always better to have the discharge higherthan the inlet as the warm diluted products of combustion will rise due to convection and be taken away. If the inlet and discharge are well over 2 mtres (6ft) from each other their height relationship is generally of little cons訩quence. It is essential to provide easy access to the fan motor to facilitate repair or maintenance. See minimum clearance figures on back cover. AIRFLOW E-Mail: info@airflow.co.uk Web Site: www.airflow.co.uk
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r r Flue Dilution Fans AIRFLOW SPECIALISTS IN AIR MOVEMENT TECHNOLOGY SINCE 1955 -
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EDILUTIONFANSIMPROVED GBDF MK5 SAFETY - NEW Differential Pressure Safety Switch for boiler shut down in the event of fan failure or blocked flue.... -
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IMPROVED GBDFMK5 TIONFANS Condensation It is recommended that drains are incorporated into the duct Systems when condensation of the combustion products... -
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EDILUTIONFANSIMPROVED GBDFMK5 New for the MK5 The new MK5 range of GBDF and SSDF fans now feature: eDifferential Pressure safety Switch which will activate... -
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AIRFLOW TM Specialists in Air Movement Technology SALESLINE 0845 330 1047 www.airflow.co.uk AIRFLOW tm Specialists in Air Movement Technology Airflow Developments...
