Greenheck Fan PN 458294 manual High Velocity Cartridge Filters Exhaust, Example

High Velocity Cartridge Filters

A. Exhaust

With all the filters in place, determine the total hood exhaust	1/4 Width
volume with a rotating vane anemometer as follows:

1.All cooking equipment should be on. If the hood has internal short circuit make-up air, it should be turned off.

2.Measuring Velocities

•Velocity measurement should be taken at three locations per filter. These must be over the inlet opening as shown in Fig. 27.

•Measure the velocity of each location. A digital 2.75 in. (70 mm) rotating vane anemometer or its equivalent is suggested. The center of the anemometer should be held 2 in. (50 mm) from the face of the filters as in Fig. 28. It is helpful to make brackets to keep the anemometer at the 2 in. (50 mm) distance and parallel to the filter. Both squareness and distance are important for accuracy.

3.Calculate the average slot velocity.

4.Calculate the CFM per linear foot by dividing the average velocity by a conversion factor listed in the following table.

5.Calculate the hood’s exhaust volume by multiplying the CFM per linear foot by the length of hood.

1/2 Width

1/4 Width

Fig. 27

2 in.

Rotating Vane

Anemometer

Fig. 28

	Cartridge Filter Size						Imperial			Metric
						Conversion Factor			Conversion Factor
	16 in. (400 mm) high with 4 in. (100 mm) high inlet						1.63	1/ft3		5.35	1/m3
	20 in. (500 mm) high with 4 in. (100 mm) high inlet						2.15	1/ft3		7.05	1/m3
	16 in. (400 mm) high with 7 in. (120 mm) high inlet						1.24	1/ft3		4.07	1/m3
	20 in. (500 mm) high with 7 in. (120 mm) high inlet						1.58	1/ft3		5.18	1/m3
Example:
Measure the slot velocities in fpm for a 9 ft. (2.74 m) hood with four 20 x 20 in. (500 x 500 mm)
filters with standard opening, three readings per filter.
									Filter Readings (fpm)
			Sum of Velocity Readings
Average slot velocity		=
									470		440	425
			Number of Readings
									482		430	453
			5330
	(Imperial)	=		= 444.2 fpm					455		431	441
			12						399		439	465
			97474
		=
	(Metric)			= 8123 m/hr					Filter Readings (m/hr)
			12
									8595		8047	7772
			Average Slot Velocity
CFM per linear foot		=							8815		7864	8284
									8321		7882	8065
			Conversion Factor
		=	444.2 fpm		= 206.6 cfm/linear foot				7297		8028	8504
			2.15
		=	8123 m/hr		= 1152 m3/hr
			7.05
Hood exhaust volume		=	CFM/linear foot (or m3/hr / m)				x Hood Length
		=			206.6		x	9 ft.	=	1859.4 cfm
		=			1152		x	2.74 m	=	3156 m3/hr

20 Proximity Hood

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