Air filters form resistance to air flow. Air filters accumulate dust and add resistance. When resistance increases to a certain resistance value, air filters are discarded. The resistance of new air filters is called "initial resistance". The resistance value corresponding to the abandonment of air filters is called "final resistance".
In design, a representative resistance value is often required to calculate the air volume of the system. This resistance is called "design resistance" which takes the average of initial resistance and final resistance.
The selection of final resistance is directly related to the service life and air volume of air filters. Usually, the selection of final resistance is the work of engineers. Experienced engineers can change the final resistance value of the original design according to the site conditions. Some designers will forget to inform users of the final resistance value they have chosen; sometimes users will change other values. At this point, the engineer has to determine the final resistance value for the model air filter or other supplier.
終阻力是初阻力的2到4倍,G3(初效過濾器)的終阻力 100~200PA、G4 在150~250 PA、F5~F6(中效) 250~300PA、F7~F8(高中效) 300~400PA、 F9~H11(亞高效) 400~450、高效與甚高效 400~600PA;
The final resistance is 2 to 4 times of the initial resistance. The final resistance of G3 (primary filter) is 100-200 PA, G4 is 150-250 PA, F5-F6 (intermediate efficiency) 250-300 PA, F7-F8 (high efficiency) 300-400 PA, F9-H11 (sub-high efficiency) 400-450, high efficiency and very high efficiency 400-600 PA.
The dirtier the air filter is, the bigger the resistance is. Excessive final resistance does not mean that the service life of the air filter is significantly improved, but it will drastically reduce the air volume of the air conditioning system. Therefore, it is not necessary to set the final resistance too high.
Low efficiency air filters often use coarse fibre filters with diameters greater than or equal to 10 mm. Because of the large aperture between fibers, excessive resistance may blow away the ash deposited on the air filters. At this time, the resistance will not increase, but the filtration efficiency will drop to zero. Therefore, the final resistance value of air filters below G4 should be strictly limited. Resistance monitoring should be installed in each filter section. Set up resistance monitoring device. The final resistance depends on the instrument, not only on the operator's feeling.