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Spring Air Systems
REV LOW
Engineering Manual Revision 2.0 -021902
14
REV LOW
Exhaust Air Calculations
Single Row Wall Mount
The Revlow Hood exhaust air formula is as follows:
Once the cooking line up has been established, the TOTAL EXHAUST (TEX) is calculated by
adding each individual NEV valve.
TEX = (NEV of appliance No. 1 + NEV of appliance No. 2 + NEV of appliance No. 3 +....)
Refer to Chart No. 4 for EXHAUST FLOW RATE (EFR) for the various types of Spring Air
Systems hoods.
The TOTAL EXHAUST (TEX) is determined by adding the NET EXHAUST VOLUME (NEV) CFM
(l/s) for each individual cooking appliance. The NET EXHAUST VOLUME (NEV) for individual
appliances varies depending on the amount of smoke, particulate, and grease generated, the
surface temperature and whether the appliance is gas or electric. Gas appliances require higher
NEV because of the high flue gas temperatures. Chart No. 4 includes typical “NEV” values for
most cooking applications. Consult the factory if an appliance is not listed.
It is important to know the dimensions of each appliance. The NET EXHAUST VOLUME (NEV)
decreases and increases proportionally to the length of some appliances. These appliances are
indicated in Chart No. 4 with length dimensions. For lengths other than indicated prorate the
value in the chart.
WARNING
The REV LOW
method is an excellent guide to assist in calculating the TOTAL
EXHAUST (TEX) volumes, but consideration must be made for the conditions
within the kitchen. i.e. location of the hood to doors, windows, and pass through
which might create a draft. Consult the factory when unusual site conditions
exist.
The total exhaust must correspond to the minimum allowable per the Spring Air
Systems UL and ULC listing. Check with factory or go directly to the UL web site
www.ul.com
The complete kitchen ventilation system must be balanced, such that a minimum
of 80% continuous heated makeup air is provided through a dedicated makeup
air system or the kitchen A/C units. It is good engineering practice to provide
this heated fresh air into the kitchen space. The heated fresh air should not
exceed 90 percent of the total exhaust volume.
Determining
REV LOW
Hood Dimensions
Hood Length:
The hood length should equal the width of all the cooking appliances to be covered by the hood
plus allow and additional 6” (152 mm) overhang on either end of the cooking line up.