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 cassette 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 + Latent 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 refrigerant 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 corrosive

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 they 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, Control 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 water 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 exhaust 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 chiller.

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 get inspected by consultant for

approval.

24. Site Installation inspection: All the site installation has to be inspected by consultant 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 tested

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