Quick Reference -HVAC (Part-1)

QUICK REFERENCE -HVAC (PART-1)

HVAC Power Consumption (IS 1391)

Cooling Capacity (Kcal/Hr) Maximum Power Consumption (KW) 3000 1.65 4S00 2.3 6000 3.1 7500 3.6 9000 4.4 1 kcal/Hr= 1.16278 watt

HVAC Noise Level (IS 1391)

Rated Cooling Capacity (Kcal/Hr) Maximum Noise Level (DBA) Indoor Outdoor 4500 or less 58 68 5000 or more 62 70

Centrifugal Fans (As per CPWD)

Type Characteristics Typical Applications Efficiency (%) Radial High pressure, medium flow, efficiency close to tube-axial fans, power increases continuously Various industrial applications, suitable for dust laden, moist air/ gases 72–79 Forward curved blades Medium pressure, high flow, dip in pressure curve, efficiency higher than radial fans, power rises continuously Low pressure HVAC, packaged units, suitable for clean and dust laden air/ gases 60–65 Backward curved blades High pressure, high flow, High efficiency, power reduces as flow increases beyond point of highest efficiency HVAC, various industrial applications forced draft fans, 79–83 Airfoil type Same as backward curved type, highest efficiency Same as backward curved, but for clean air applications 79–83

Axial Flow Fans (As per CPWD)

Type Characteristics Typical Applications Efficiency (%) Propeller Low pressure, high flow, low efficiency, peak efficiency close to point of free air delivery (zero static pressure) Air-circulation, ventilation, exhausts. 45–50 Tube axial Medium pressure, high flow, higher efficiency than propeller type, dip in pressure-flow curve before peak pressure HVAC, drying ovens, exhaust Systems 67–72 Vane axial High pressure, medium flow, dip in pressure-flow curve, use of guide vanes improves Efficiency exhausts High pressure applications including HVAC systems 78–85

Thickness of sheets for Rectangular Ductwork (As per CPWD)

Longest side (mm) Minimum sheet thickness For GSS For Aluminum 750 mm and below 0.63 mm 0.8 mm 751 mm to 1500 mm 0.8 mm 1 mm 1501 mm to 2250 mm 1 mm 1.5 mm 2251 mm & above 1.25 mm 1.8 mm All ducts shall be fabricated either from Galvanized Sheet Steel (GSS) conforming to IS: 277 or aluminum sheets conforming to IS:737. The steel sheets shall be hot dip galvanized with MAT finish with coating of minimum 120 grams per square meter (GSM) of Zinc, GI sheets shall be lead free, eco friendly and Ro HS compliant

Thickness of sheet for Round Ducts (As per CPWD)

Diameter of duct, mm Thickness of Sheet For GSS For Aluminum 150 to 500 mm 0.63 mm 0.8 mm 501 to 750 mm 0.8 mm 0.8 mm 751 to 1000 mm 0.8 mm 1 mm 1001 to 1250 mm 1 mm 1.5 mm 1251 mm and above 1.25 mm 1.8 mm All sheet metal connections, partitions and plenums required for flow of air through the filters, fans etc. shall be at least 1.25 mm thick galvanized steel sheets, in case of G.I. sheet ducting or 1.8 mm thick aluminum sheet, in case of aluminum sheet ducting and shall be stiffened with 25 mm x 25 mm x 3 mm angle iron braces. Circular ducts, where provided shall be of thickness as specified in IS: 655 as amended up to date. Aluminum ducting shall normally be used for clean room applications, hospitals works and wherever high cleanliness standards are functional requirements

Duct’s Associated Items

Application Duct Width Angle size Flanges Up to 1000 mm 35 mm x 35 mm x 3 mm Flanges 1001 mm to 2250 mm 40 mm x 40 mm x 3 mm Flanges More than 2250 mm 50 mm x 50 mm x 3 mm Bracings Up to 1000 mm 25 mm x 25 mm x 3 mm Bracings More than 1000 mm 40 mm x 40 mm x 3 mm Support angles Up to 1000 mm 40 mm x 40 mm x 3 mm Support angles 1001 mm to 2250 mm 40 mm x 40 mm x 3 mm Support angles More than 2250 mm Size and type of RS section shall be decided in individual cases Hanger rods shall be of mild steel and of at least 10 mm dia for ducts up to 2250 mm size, and 12 mm dia for larger sizes All nuts, bolts and washers shall be zinc plated steel. All rivets shall be galvanized or shall be made of magnesium – aluminum alloy. Self tapping screws shall not be used.

Comparison of the VRF/ VRV systems with the Central Chilled water system (As per CPWD)

Points VRF AC Chilled Water based AC Remarks System Base It is Gas Base System It is Water Base System Peak Power Demand 1.6KW/TR peak. (Efficiency drastically reduces at high ambient) 1.3KW/TR Peak. (IKW/TR<0.6 now for chilling units.) Higher size & cost of Power Supply Capital Equipment like Transformers etc. & thus higher Cu losses in VRF system. Annual Power Consumption 1.15 to 1.20 1 Annually extra expenditure of 15 to 20% in electricity bills in VRF system. Security & Safety of Equipment & System Copper piping on terrace & in building MS piping VRF system equipments/ materials prone to theft & damage by miscreants Terrace Space Almost 80% terrace is used for ODUs & Cu pipe & power cables Only Cooling Towers need to be installed at terrace. Problem of cleaning terrace & loss of water proofing also occurs over time. Water Scarcity No water require…