15.0 Math Review 14.5 Using Basic Formulas

Converting Units Converting 6 inches of Mercury into Inches of Water Inches of Mercury are multiplied by 13.6 to get inches of water 6” of Mercury = 13.6 x 6 = 81.6 inches of water Note: 81.6” ÷ 12” = feet of water = 6.8’

Converting Units Convert 82 Inches of Water to Inches of Mercury Inches of water are multiplied by to get Inches of Mercury 82” x = 6.027” of Mercury

Converting Units LPS x = CFMCFM x 2.12 = LPS HP x = Kilowatts1Watt = Btu/h Ft of H 2 O x = psipsi x 2.31 = Ft of H 2 O [F 0 – 32] x 5/9 = C 0 [C 0 x 9/5] + 32 = F 0 h = P psia ÷ 0.433P psia = psi Tons of Refrigeration = HP x Tons of Refrigeration = BTU/minute x 200 Note: HP x = Btu/minute x 200

Converting Units Square inches are divided by 144 to get square feet 72 in 2 = ? Ft 2 72 ÷ 144 = 0.5 Ft 2 Note: Ft 2 x 144 = in 2

Using Equations = = 2 3 = 3 x x 200

Using Equations Fan Law CFM new CFM old RPM old RPM new = CFM new CFM old = RPM new RPM old

Using Equations = x 2 3 = x x 3 2 = 600

Using Equations Fan Law CFM new CFM old RPM old RPM new = CFM new CFM old = RPM new RPM old x

Using Equations Fan Law CFM new CFM old RPM old RPM new = CFM new CFM old ? RPM new RPM old = 875 = 555 = 1100

Using Equations Fan Law RPM new = CFM new CFM old ? RPM new RPM old = 875 = 555 = 1100

Using Equations Fan Law RPM new = = x RPM new =

Using Equations Fan Law CFM new CFM old RPM old RPM new = CFM new CFM old = RPM new RPM old x

Percent of Design If we measured 147 CFM of air and the design value wanted was 150 CFM: How would that be converted to % of design? Number Found ÷ Design Value x 100 = % of Design 147÷ 150 x 100 = % of Design 98%

Percent of Design If we measured 171 CFM of air and the design value wanted was 150 CFM: How would that be converted to % of design? Number Found ÷ Design Value x 100 = % of Design 171÷ 150 x 100 = % of Design 114%

Averaging Add up the numbers you have and divide that answer by the total of the numbers you have. Example for the number of people at work: Monday = 15 Tuesday = 17 Wednesday = 18 Thursday = 18 Friday = = ÷ 5 = 16

Averaging Monday $7.80 Tuesday $6.72 Wednesday $7.83 Thursday $10.57 Friday $9.56 Don’s Average Lunch Cost For The Week + $42.48

Averaging Monday $7.80 Tuesday $6.72 Wednesday $7.83 Thursday $10.57 Friday $9.56 Don’s Average Lunch Cost For The Week $ ÷ 5 = Average = or $8.50

Traverse Readings/Measurements abcd Airflow measured in feet per minute (fpm) for 8” round duct.

Traverse Readings/Measurements abcd

Traverse Readings/Measurements abcd

Traverse Readings/Measurements abcd

Traverse Readings/Measurements abcd

Traverse Readings/Measurements abcd = ÷ 12 = or 355 fpm