Calculate Size of Lift Lobby Pressurization Fan for Highrise Building

Calculate Size Lift Lobby Pressurization Fan having following Details

• Type of Building:
• Type of Building is Commercial and Sprinkler Protected
• Lift Door Detail:
• Number of Lift Door (Basement to Terrace) (B+G+15) is 17 Nos
• Lift Door width is 1 meter and Height is 2.2 meter.
• Lift Lobby Detail:
• Width of Lift Lobby area for each Floor is 3.6 Meter
• Length of Lift Lobby area for each Floor is 3.6 Meter
• Height of Lift Lobby area for each Floor is 3.0 Meter
• No of Floor Door Opening in Lift Lobby Area (Single Leaf Door) is 18 Nos.
• Lift Lobby Door/Floor Door width is 1 meter and Height is 2.2 meter.
• Design Pressure Difference:
• Consider Pressure difference is 12.5 Pa
• Air Velocity across door is 0.75 m/sec

Calculation: 

• Air Leakage are calculated on following areas
• Leakages through Lift Lobby Door / Floor Door on each Floor
• Leakage through Lift Lobby Area
• Leakages through lift Doors on each Floor
• Open Lift Door and Lift Lobby Door

(1) Leakages through Lift Lobby Door / Floor Door on each Floor

• No of Floor door (Single Leaf) is 18 Nos
• Leakage Area around the Door as per BS:5588 = 0.01m2

• Total leakage area all doors on all floors (A1): No of Door x Leakage area around Door
• Total leakage area all doors on all floors (A1):18 x 0.01
• Total leakage area all doors on all floors (A1):0.18 m2

(2) Leakages through lift Lobby Area

(a) Leakage through Lift Lobby:

• Lift Lobby Wall Perimeter = 2 x (Lift Lobby Width + Lift Lobby Length)
• Lift Lobby Wall Perimeter =2 x (3.6+3.6)
• Lift Lobby Wall Perimeter =14.4 Meter
• Leakage Area through Lift Lobby = Lift Lobby Perimeter x Lift Lobby Height
• Leakage Area through Lift Lobby =14.4 x 3.0
• Leakage Area through Lift Lobby =43.2 Meter
• Leakage Area Ratio for Lift Lobby: (A/Aw) =0.00084 as per NFPA 92A

• Effective leakage Area (a)= Leakage Area Ratio for Lift Lobby x Leakage Area through Lift Lobby.
• Effective leakage Area (a)= 0.00084 x 43.2
• Effective leakage Area (a)=0.036 m2

(b) Leakages through Lift doors

• No of Lift Door =17 Nos
• Leakage Area around the Lift Door as per BS:5588 = 0.06m2
• Leakage area around lift doors (b): No of Lift Door x Leakage around Lift Door
• Leakage area around lift doors (b): 17 x 0.06
• Leakage area around lift doors (b): 1.020 m2
• Total Leakage Area(A2) =a+b =0.036+1.020= 1.056 m2
• Effective Leakage Area (Ae)= A1 x A2 / (A12 + A22)0.5
• Effective Leakage Area (Ae)= 0.18 x 1.056 / (0.18 + 1.056) 0.5
• Effective Leakage Area (Ae)= 0.521 m2

(3) Open Lift Lobby Doors (Floor Doors) & Lift Doors

(a) No of Open Lift Door:

• No of Open Lift Door = 0 Nos
• Lift Door Area = Lift Door Width x Lift Door Height
• Lift Door Area = 1.0 x 2.2
• Lift Door Area =2.2 m2
• Open Lift Door Area = No of Open Lift Door x Lift Door Area
• Open Lift Door Area = 0 x 2.2
• Open Lift Door Area (a) = 0.0 m2

(b) No of Open Lift Lobby Door / Floor Door:

• No of Open Lift Door = 1 Nos
• Lift Door Area = Lift Lobby Door Width x Lift Lobby Door Height
• Lift Door Area = 1.0 x 2.2
• Lift Door Area =2.2 m2
• Open Lift Lobby Door Area = No of Open Lift Lobby Door x Lift Lobby Door Area
• Open Lift Door Area =1 x 2.2
• Open Lift Door Area (b) = 2.2 m2
• Total Open Lift Door & Lift Lobby Door Area = a+b = 0+ 2.2 = 2.2 m2
• Velocity through Open Door = 0.75 meter/sec (*As per BS 5588: Part-4)
• Air Flow through open doors = Air Velocity x Open Lift Door Area
• Air Flow through open doors = 0.75 x 2.2
• Air Flow through open doors =1.650 m3/sec

Calculate Air Flow for Lift Lobby Pressurization

• Air Flow for Lift Lobby Pressurization = 0.839 x Ae x (ΔP)1/2
• Minimum Design Pressure difference for Lift Lobby pressurization (ΔP) = 50pa (*As per BS 5588)
• Minimum Design Pressure difference for Lift Lobby pressurization (ΔP) = 50pa (*As per NBC 2016)
• Minimum Design Pressure difference for Lift Lobby  pressurization (ΔP) = 10pa (*As per NFPA 92A)
• Consider Design Pressure difference for Lift Lobby  pressurization (ΔP) = 12.5pa

•  Air Flow for Lift Lobby Pressurization = 0.839 x 0.521x (12.5)1/2
• Air Flow for Lift Lobby Pressurization = 0.521 m3/sec
• Total Air Flow for Lift Lobby Pressurization = Air Flow for Lift Lobby Pressurization+ Air Flow through open doors
• Total Air Flow for Lift Lobby Pressurization = 0.521 + 1.650
• Total Air Flow for Lift Lobby Pressurization = 2.171 m3/sec
• Consider Safety Factor =10 %
• Total Air Flow for Lift Lobby Pressurization = 2.171 x 1.1
• Total Air Flow for Lift Lobby Pressurization =2.388 m3/Sec
• Total Air Flow for Lift Lobby Pressurization =2.388 x 2118.88
• Total Air Flow for Lift Lobby Pressurization =5059 CFM

Conclusion:

• Capacity of Lift Lobby Pressurization Fan = 5059 CFM