1. Basics of Heat load : Heat gain to the building: Sensible heat: mostly from sun, heat dissipation from machines, electric lighting, electrical panels, people, outside fresh air. Latent Heat: From people, outside fresh air. 2. Types of HVAC units: Window A/C Units Mini Split A/C Units (Wall mount or ceiling mount or c assette type) Ducted split A/C Units Package A/C Units Air cooled water chillers Water cooled water chillers Vapour Absorption Machines 3. Selection of Package A/C, Duct Split A/C Units,: Based on; Cooling capacity (Total & sensible heat), Total heat = Sensible heat + Latent heat Heating capacity for Electric Heater (if heater is required) Air flow External static pressure Ambient air condition: Dry bulb temperature Power supply for the A/C Unit Vapour Absorption Machines 4. Selection of Chilled Water AHU Cooling capacity (Total & sensible heat), Total heat = Sensible heat + L atent heat Heating capacity for Electric Heater (if heater is required) Air flow (CFM) Chilled water flow (GPM) Entering & Leaving Chilled Water Temp into cooling coil External static pressure Power supply for the A/C Unit 5. Difference between DX-AHU and Chilled water AHU DX-AHU: It is the indoor unit if split A/C Unit where the re refrigerant frigerant flows into the cooling coil. Chilled water AHU: The chilled water flows into the cooling coil coming from the chiller. 6. Main components of Package A/C Unit : Blower Evaporator (DX-cooling coil) made of copper tubes and aluminum fins Compressor Condenser coil made of copper tubes and aluminum fins. (For coastal and cor rosive environment, the condenser coil should be made of Copper tubes and copper fins)
7. Main components of Ducted split A/C Unit : It is splitted into outdoor unit and indoor unit and t hey are connected through Refrigerant piping. Outdoor unit: Compressor and condenser coil Indoor Unit: DX-Cooling coil and blower. 8. Critical Facilities: All critical facilities like Operation theatre rooms, Contr ol rooms, data centres, communication rooms, switchgear rooms and electric substations should have duty & standby A/C Units. 9. Installation of Roof top Package A/C Units: Need to check the following before installation; Location of the unit as per approved drawings Readiness of concrete foundation and inspection clearance from civil Arrangement of proper crane with proper documents Should have the approved method statement for the installation of unit. 10. Fabrication of HVAC Ducts: Before stating the fabrication, make sure it is as per approved drawings and site conditions. 11. Installation of ducts : Need to check the following before starting the installation Should have approved shop drawing & coordination drawing and method statement for the installation of ducts. Cross check as per the site condition Material inspection to be done Duct s to insulated (leaving the joints for smoke testing) before installation in order to save time. 12. Access doors: For all motorized dampers, fire dampers, duct heaters. 13. Identify the supply and return diffusers: Supply diffusers will be with inbuilt damper and return diffuser will be without damper. 14. Back draft damper: It is like a check valve and required in case of duty & standby units connected to common main supply & return duct to backflow in standby unit. 15. Types of most commonly used VAV : By pass VAV and Shut off VAV By pass VAV: It is controlled through room thermostat and depending upon the room temperature setting, supplies the required air flow to the room and by pass the applicable amount of air to the ceiling and will return back to AHU.It varies the air flow in room and keeps the constant air flow in ducting. It is similar to 3-way modulating valve in chilled system which in installed in return piping of the chilled wate r AHU. Modulating VAV: It is controlled through room thermostat and depending upon the room temperature setting, supplies the required air flow to the room and shut off the VAV which increases the air pressure inside the ducting. It varies the air flow in room and also inside the ducting. With modulating VAV,the AHU blower motor should be with VFD in order to vary the air flow. It is similar to 2-way modulating valve in chilled system which in installed in return piping of the chilled water AHU.
16. Coordination for A/C Units; Civil: Concrete foundation for A/C Units Electrical: Power supply to the A/C Units HVAC Control: Interfacing with control system Fire Alarm: Interfacing with Fire Alarm system 17. Types of duct insulation Fiberglass insulation Rockwool insulation Closed cell rubber insulation 18. Types of Chilled water piping insulation Fiberglass insulation Rockwool insulation Polyurenated Foam Closed cell rubber insulation 19. Material take-off for; Ducting & insulation Grills & Diffusers, dampers Duct & Pipe supports Piping, Valves, Flanges, Nuts & Bolts 20. Battery Room: The ducting & Grills should be stainless steel and e xhaust fan (1 duty + 1 standby) should be explosion proof. 21. Chilled Water Primary & secondary pumps : Primary Pumps: Mostly constant flow and pumps the return chilled water through chillers and up to the suction of secondary pumps. Secondary Pumps: If the AHUs are with 2-way modulating valves, the this pump motor should be with VFD to vary the flow to the AHUs.Usually it is installed after the c hiller. If the AHUs are with 3-way modulating valves, then no need of VFD,it will give constant water flow. 22. Chilled Water Piping connections, Valves to AHU: Inlet : Isolation Valve (Butterfly Valve),Strainer,drain,locating pressure & temperature gauges outlet : Balancing Valve,2-way/3-way modulating valve, Isolation Valve (Butterfly Valve),,drain, locating pressure & temperature gauges 23. Material Inspection: Before installation, all the material has to g et inspected by consultant for approval. 24. Site Installation inspection: All the site installation has to be inspected by c onsultant for approval. 25. How to prioritize the site activities to give clearance to other services 26. Smoke test : to check air leakage in ducting 27. Testing, Adjusting & Air Balancing (TAB)
28. Commissioning of A/C Units : Make sure that the ; All the ducting is completed and duct connection to the unit. All refrigerant piping is completed and leak teste d Power supply to the unit All the dampers are fully open
29. Commissioning of Chillers : Make sure that the; All the piping is completed and piping connection to the Chillers, Pumps & AHU. All the chilled water piping is completed and leak tested and flushing and chemical treatment is done Water balancing Power supply to the Chillers
