1. What is a fire fighting system?

It’s a system designed to detect, control, and extinguish fires in buildings or facilities.

2. What is NFPA?
National Fire Protection Association – it develops fire safety standards.

3. Types of fire extinguishers?

Water, Foam, CO₂, Dry Powder, Wet Chemical.

4. Classes of fire?
A (solids), B (liquids), C (gases), D (metals), K (cooking oils).

5. What is a sprinkler system?

An automatic water discharge system triggered by heat.

6. Types of sprinkler systems?

Wet, Dry, Pre-action, Deluge.

7. What is the purpose of a fire pump?

To boost water pressure for fire suppression systems.

8. Types of fire pumps?

Centrifugal, vertical turbine, end suction, split case.

9. What is a jockey pump?

Maintains system pressure in fire fighting piping.

10. What is a standpipe system?

Vertical pipes for firefighting hose connections in buildings.

11. Classes of standpipe?

Class I, II, III (based on use and equipment connection).

12. What is fire hydrant system?

External or internal system for fire department hose connection.

13. Fire hydrant pressure range?

7 to 10 bar typically.

14. What is a fire alarm panel?

Central hub that monitors and signals fire alarms.

15. What is a zone in fire alarm systems?

A division in a building for monitoring specific fire areas.

16. What is a fire detector?

Device that detects smoke, heat, or flame.

17. Types of fire detectors?

Smoke, Heat, Flame, Multi-sensor.

18. What is a smoke detector?

Device that senses airborne particles from smoke.

19. What is a heat detector?

Senses temperature rise due to fire.

20. Fire suppression system types?

Water-based, Gas-based (FM-200, CO₂), Foam, Powder.

21. What is FM-200?

Clean agent gas for fast fire suppression.

22. What is CO₂ system?

Gaseous fire suppression for sensitive equipment rooms.

23. What is fire load?

Total combustible material in a building space.

24. What is fire rating?

Time material resists fire (e.g., 1-hour, 2-hour).

25. What is fire compartmentation?

Dividing building to contain fire spread.

26. What is ELCB/MCB in fire safety?

Prevents electrical fire by tripping during faults.

27. What is fire drill?

Mock fire evacuation to train personnel.

28. What is a fire escape plan?

Pre-defined evacuation route and procedure.

29. What is fire extinguisher rating?

Indicates effectiveness against different fire classes.

30. What is fire risk assessment?

Inspection to identify fire hazards and safety gaps.

31. What is a two-stage alarm?

First alert, second for evacuation.

32. What is fire damper?

Closes air duct to block fire spread.

33. What is smoke control system?

Removes smoke from fire-affected areas.
34. Fire alarm battery backup time?
Typically 24–72 hours.

35. What is a VESDA system?

Very Early Smoke Detection Apparatus using air sampling.

36. What is fire hose reel?

Wall-mounted hose for manual firefighting.

37. What is the unit of Overall Heat Transfer Coefficient (U)?

As we know

Q = U × A × ΔT

Where:

 Q = Heat (unit: Watt)

 A = Area (unit: m²)
 ΔT = Temperature difference (unit: K)
 U = Overall Heat Transfer Coefficient (we want its unit)

Formula Rearranged:

U = Q / (A × ΔT)

Now plug in units:

U = W / (m² × K)
✅ So, Unit of U is: → W / (m²·K)

Overall Heat Transfer Coefficient unit = W/(m²·K)

38. What is the unit of Thermal Resistance (R)?

Thermal Resistance (R) is the opposite (inverse) of U.

R = 1 ÷ [W / (m²·K)]

🔹 Core Concepts

1. What is the refrigeration cycle and name its components?

✅ It consists of Evaporator → Compressor → Condenser → Expansion Valve, forming a
closed loop to remove heat from indoor air.

2. What is 1 TR (ton of refrigeration) and how is it calculated?

✅ 1 TR = 12,000 BTU/hr ≈ 3.517 kW. It’s the cooling needed to freeze 1 ton of water
into ice in 24 hours.

3. What is the difference between air-cooled and water-cooled chillers?

✅ Air-cooled uses air to reject heat; water-cooled uses cooling tower water. Water-
cooled is more efficient but needs more infrastructure.

4. What is delta-T in HVAC, and why is it important?

✅ Delta-T = Supply temp – Return temp. Shows how much heat is removed; affects
chiller/pump performance.

5. Explain the function of the expansion valve in a refrigeration system.

✅ It drops refrigerant pressure and temperature before it enters the evaporator,
enabling cooling.

🔹 System Types & Design

6. What is the difference between AHU and FCU?

✅ AHU is a large air-handling unit connected to ductwork; FCU is compact, installed in
rooms, and serves individual zones.

7. What is a VAV system and where is it used?

✅ Variable Air Volume system adjusts airflow based on demand. Used in offices, malls,
and hospitals.

8. What are the components of a ducted HVAC system?

✅ AHU/FCU, ducts, diffusers/grilles, dampers, and controls.

9. How do you perform cooling load calculations for a room?

✅ Based on area, orientation, occupancy, equipment, lights, and ventilation. Result is
expressed in TR or kW.

10. Explain the difference between DX and VRF systems.

DX uses refrigerant directly inside evaporator; VRF uses multiple indoor units with
inverter outdoor unit, modulating refrigerant flow.

🔹 Piping & Pumps

11. What is the function of a decoupler in a chilled water system?

✅ It separates primary (chiller) and secondary (building) loops to prevent flow conflict.

12. What is the ideal velocity for chilled water in piping?

✅ Main line: 8–10 ft/s; branch line: 4–6 ft/s to reduce noise and erosion.

13. How do you size a chilled water pipe?

✅ Based on flow rate, velocity, and pressure loss using charts or software.
14. What is the difference between static and dynamic balancing?
✅ Static: manual valve setting; Dynamic: automatic valve adjustment (e.g., PICV).

15. What is a PICV (Pressure Independent Control Valve)?

✅ A valve that ensures constant water flow regardless of system pressure changes.

1. CFM per Ton of Cooling

• Standard Rule: 400 CFM per TR (1 TR = 400 CFM)
• Use this to quickly estimate air quantity required for any space
• For data centers or high-heat areas, consider 350 CFM per TR

2. TR per Square Foot (Cooling Load Estimate)

• Comfort Cooling (Offices, Homes): 1 TR per 400 to 500 sq.ft
• Restaurants, Gyms, Retail: 1 TR per 250 to 300 sq.ft
• Server Rooms or Kitchens: 1 TR per 100 to 150 sq.ft

This helps with early system sizing

3. Duct Sizing Thumb Rule

• Supply Duct Velocity: 800 to 1200 FPM
• Return Duct Velocity: 600 to 900 FPM
• Approximate duct surface area: 0.15 to 0.18 sq.m per CFM

4. Chilled Water Flow Rate

• Shortcut formula: 2.4 GPM per TR (for ΔT = 10°F)
• Use for pump and pipe sizing in early design stages

5. Condensate Drain Pipe Size

• Up to 2 TR: 20 mm
• 2 to 5 TR: 25 mm
• Above 5 TR: 32 mm or more
• Maintain slope of 1 in 100 minimum

6. Fresh Air Requirement

• Office: 5 to 10 CFM per person
• Gym or densely occupied areas: 15 to 20 CFM per person

7. Fan Power Estimation

• Quick estimate: 1.5 to 2.0 kW per 1000 CFM
• Fine-tune later using total pressure and efficiency

8. VRF Piping Rules

• Indoor unit distance limit: 50 meters
• Total piping length: usually within 150 meters
• Vertical separation: up to 15 meters between units
AHU Blower Housing Replacement involves removing and replacing the enclosure or
casing that supports and directs the airflow around the blower (fan) in an Air Handling
Unit (AHU). Here's a general guide to the process:

🔧 Tools & Materials Needed:

New blower housing assembly

Puller
File
Sand paper
Grease
Hand drill
Hammer
Allen Key set
SKF Belt alignment tools
Tachometer
Amps Meter
Socket set
Open and Ring Spinner
WD40
screw drivers
Safety gear (gloves, goggles, etc.)

📋 Step-by-Step Procedure:

1. Safety First
Turn off the power supply to the AHU.
Lockout/Tagout (LOTO) the system to prevent accidental startup.

2. Access the Blower Section

Open the AHU panels.
Remove any insulation or obstructions around the blower section.

3. Disconnect the Blower Assembly

Disconnect motor electrical connections.
Loosen the belts or remove the coupling (if applicable).
Remove bolts or fasteners holding the blower and housing.

4. Remove the Existing Blower Housing

Carefully lift out the blower and housing assembly.
Detach the blower wheel and motor (if reusing).
Inspect blower wheel and motor for wear/damage.

5. Install the New Housing

Place the new blower housing in position.
Mount the blower wheel and motor onto the new housing.
Ensure proper alignment and balance.

6. Reconnect Components
Fasten the blower housing securely.
Reconnect electrical wiring and belts/coupling.
Check alignment and pulley tension.

7. Seal and Insulate

Apply sealant or gasket to prevent air leaks.
Replace insulation if removed.

8. Testing & Commissioning

Remove LOTO and power on the AHU.
Test run the blower.
Check for vibration, noise, and airflow.
Verify ampere readings and RPM.

📝 Notes:

Ensure the replacement housing matches the original dimensions and capacity.

Always verify blower wheel clearance and alignment to avoid imbalance or vibration.

If the blower or motor is damaged, consider replacing it along with the housing.
Thanks

Q1. Purpose of a decoupler in a primary-secondary chilled water system?

Answer:
A decoupler is a pipe that connects the primary (chiller) loop and secondary
(building) loop in a chilled water system. Its purposes are:

 Ensures constant flow through chillers: Chillers require a steady

flow rate to operate efficiently. The decoupler prevents flow variations
in the building loop from affecting the chiller loop.

 Separates variable flow in the building loop: As air handling units

(AHUs) or fan coil units (FCUs) adjust their water flow based on cooling
demand, the decoupler allows this variability without disrupting chiller
operation.

Why it matters: Without a decoupler, variable building flow could cause

low-flow or high-flow issues in chillers, leading to inefficiency or damage.
Q2. Define TR. How is it related to kW?

Answer:

 TR (Ton of Refrigeration): A unit of cooling capacity.

o 1 TR = 12,000 BTU/hr (British Thermal Units per hour).

o 1 TR ≈ 3.517 kW (kilowatts).

Why it matters: TR measures cooling capacity, while kW measures power

consumption. This relationship helps size equipment and calculate energy
efficiency.

Q3. Ideal velocity range in supply air ducts?

Answer:

 Main ducts: 1000–1500 FPM (feet per minute).

 Branch ducts: 600–1000 FPM.

Why it matters:

 Too high velocity causes noise and pressure drops.

 Too low velocity leads to poor air distribution and larger duct sizes.
Q4. Why insulate chilled water pipes?

Answer:

 Prevents condensation: Cold pipes can sweat in humid

environments, causing water damage or mold.

 Reduces energy loss: Insulation minimizes heat gain from

surroundings, improving system efficiency.

Why it matters: Uninsulated pipes waste energy and risk structural

damage.

Q5. Function of a Volume Control Damper (VCD)?

Answer:

 Regulates airflow: Adjusts the amount of air passing through ducts.

 Balances the duct system: Ensures even air distribution to all zones.

Why it matters: Proper balancing avoids hot/cold spots and optimizes

energy use.
Interview Round 2

Q1. Function of a differential pressure sensor?

Answer:
Measures the pressure difference between supply and return pipes in a
chilled water system. It signals the Variable Frequency Drive (VFD) to
adjust pump speed, maintaining optimal pressure and flow.

Why it matters: Saves energy by avoiding constant full-speed pump

operation.

Q2. Define U-value.

Answer:

 U-value = Heat transfer rate (W/m²·K).

 Lower U-value = Better insulation (less heat passes through).

Why it matters: Critical for selecting insulation materials to reduce energy

loss.

Q3. Difference between DX and VRF systems?

Answer:

 DX (Direct Expansion):
o Uses refrigerant directly in cooling coils (e.g., split ACs).
 o Simpler but less efficient for large spaces.

 VRF (Variable Refrigerant Flow):

o Uses multiple indoor units connected to one outdoor unit with
inverter compressors.

o Adjusts refrigerant flow based on demand (energy-efficient for

zoning).

Why it matters: VRF is better for large/commercial buildings; DX is cheaper

for small spaces.

Q4. Maximum velocity in chilled water piping?

Answer:

 Main pipes: 8–10 ft/s.

 Branch pipes: 4–6 ft/s.

Why it matters: High velocity causes erosion, noise, and pressure drops.

Q5. How does a VFD save energy?

Answer:
A VFD adjusts motor speed to match system load (e.g., reducing pump speed
at partial load). This cuts power consumption significantly compared to fixed-
speed motors.
Why it matters: Can reduce energy use by 30–50% in HVAC systems.

Interview Round 3

Q1. Minimum slope for chilled water piping?

Answer:
1:500 to 1:1000 (1 mm drop per 500–1000 mm of pipe length).

Why it matters: Ensures air collects at high points (for vents) and water
drains properly.

Q2. How to size a chilled water pipe for 300 GPM?

Answer:

1. Use pipe sizing charts (e.g., ASHRAE tables).

2. Ensure velocity <8 ft/s.

3. Calculate pressure loss (friction) to select pump capacity.

Why it matters: Oversized pipes waste material; undersized pipes increase

pump energy.
Q3. What is PICV?

Answer:
Pressure Independent Control Valve: Maintains constant flow to coils
even if system pressure fluctuates.

Why it matters: Improves system stability and eliminates manual

balancing.

Q4. What is short cycling?

Answer:
Frequent compressor ON/OFF cycles due to improper sizing or faulty
controls.

Why it matters: Wears out compressors and wastes energy.

Q5. Explain coil delta-T.

Answer:
Temperature difference between chilled water supply (e.g., 6°C) and return
(e.g., 12°C) across a coil. A low delta-T indicates poor heat transfer (e.g.,
dirty coil).

Why it matters: Key for diagnosing system efficiency.

Interview Round 4

Q1. How to verify an AHU is ready for commissioning?

Answer:
Check:

 Filters, dampers, and valves are installed.

 Electrical connections are secure.

 No obstructions in ducts.

 BMS sensors are calibrated.

Why it matters: Ensures safe and efficient operation.

Q2. BMS actuator in a VAV system?

Answer:
Modulates damper position based on temperature or BMS signals to control
airflow to zones.

Why it matters: Critical for zoning and energy savings.

Q3. How to check chilled water flow direction?

Answer:

1. Look for flow arrows on pipes.

 2. Touch pipes: cooler = supply, warmer = return.

3. Use a flow meter.

Why it matters: Reverse flow can damage equipment.

Q4. What is free cooling?

Answer:
Using cool outdoor air (via economizers) instead of running chillers in mild
weather.

Why it matters: Saves significant energy.

Q5. Typical HVAC shop drawing contents?

Answer:

 Duct/piping layouts.

 Equipment locations.

 Dimensions and access points.

Why it matters: Blueprint for installation.

Interview Round 5

Q1. Decoupler line in a chiller plant?

Answer:
Hydraulically separates primary (chiller) and secondary (building) loops to
allow variable flow in the building while keeping chiller flow constant.

Why it matters: Prevents flow conflicts and protects chillers.

Q2. Air-cooled vs. water-cooled chillers?

Answer:

 Air-cooled: Simpler, no cooling tower, but less efficient.

 Water-cooled: More efficient but needs cooling towers and more

maintenance.

Why it matters: Choice depends on space, budget, and efficiency needs.

Q3. How does a VFD help in chiller pump systems?

Answer:
Adjusts pump speed to match load, reducing energy use and wear.

Why it matters: Major energy saver in variable flow systems.

Q4. BMS points monitored in a chiller?

Answer:

 Chilled water supply/return temps.

 Pump status.

 Pressure readings.

 Alarm signals.

Why it matters: Ensures optimal performance and quick fault detection.

Interview Round 6

Q1. Purpose of flushing chilled water pipes?

Answer:
Removes debris to prevent clogging coils, valves, and pumps.

Why it matters: Dirty pipes can damage equipment.

Q2. Hydrostatic test pressure for chilled water piping?

Answer:
1.5 times operating pressure (e.g., 150 psi for a 100 psi system).

Why it matters: Ensures pipes can handle pressure without leaks.

🏗️Types of Water Distribution Systems in Multi-storeyed Buildings :
1. Direct supply systems from mains.
2. Gravity distribution system.
3. Hydro-pneumatic system.
4. Combined distribution system.

Gravity Water Distribution System : This is the most common water distribution system.
This system comprises pumping water to one or more overhead tanks. Water
transferred to overhead tanks is distributed by gravity to various parts of the building
by the system of piping network.

🏢 Gravity Water Distribution System – Main Components

🔷 1. Water Source
. Municipal Supply or Borewell
Source of raw water for the entire building.

🔷 2. Underground Water Tank (UGT)

. Located at the basement or ground level.
Acts as the primary storage for raw water from municipal lines or borewells.
Divided into:
. Raw Water Compartment (for untreated water)
. Treated Water Compartment (post-WTP)
. Flushing Water Compartment (may include STP-treated water)

🔷 3. Water Treatment Plant (WTP)

. Treats raw water from the underground tank to potable standards.
Involves:
. Sand filters
. Activated carbon filters
. Chlorination or UV disinfection

🔷 4. Sewage Treatment Plant (STP)

. Treats wastewater (grey & black water) from the building.
Treated water is reused for:
. Toilet flushing
. Gardening
. Cooling towers (if applicable)

🔷 5. Overhead Tank (OHT) / Roof Tank

. Located on the rooftop or upper terrace.
. Segregated compartments:
. Domestic Water
. Flushing Water
. Fire Fighting (if needed)
. Receives water from UGT (pumped) and distributes via gravity.

🔷 6. Terrace Ring Main System

. Circular loop of pipes around the terrace, connected to the OHT.
. Ensures even distribution and pressure balancing for water to different risers.
. Reduces stagnation and improves flow efficiency.

🔷 7. Gravity Downfeed Risers

. Vertical pipes carrying water from OHT to different floors.
. Two primary systems:
. Domestic Riser: For potable use (sinks, showers, kitchen).
. Flushing Riser: For WC/urinals using STP-treated or separate flushing supply.

🔷 8. Zoning & Pressure Control

. In high-rise buildings, use:
. Pressure Reducing Valves (PRVs) to prevent over-pressure.
. Divide building into hydraulic zones (typically every 10–12 floors).

🔷 9. Internal Distribution System

. Horizontal branches from risers on each floor to fixtures.
. Include:
. Taps, showers, washing machine inlets (domestic)
. Toilets, urinals (flushing)

🔷 10. Valves & Controls

. Float valves in tanks
. Gate valves/ball valves for isolation
. Check valves (non-return) in pump lines
. Water level sensors for automation
. Meters for monitoring usage

🌬️Air Handling Unit (AHU) – Essentials You Should Know ✅‼️

📘 Definition

An Air Handling Unit (AHU) is a central component in HVAC systems, responsible for
conditioning and circulating air within a building.

🛠️Key Components

1. Fans –
➤ Supply and return fans move air through the duct system.

2. Coils –
➤ Heating (electric, steam, or hot water) and cooling (chilled water or refrigerant) coils
adjust air temperature.

3. Filters –
➤ Trap dust, allergens, and other airborne contaminants.
4. Dampers –
➤ Regulate airflow volume, mix outdoor and return air, and improve comfort and
efficiency.

⚙️Core Functions

🔥 Heating – Warms air before distribution.

❄️Cooling – Removes heat from air.

🌬️Ventilation – Introduces fresh outdoor air, diluting indoor pollutants.

🧼 Air Filtration – Enhances air quality by capturing particulates.

🏢 Applications

1. Commercial Buildings
🏨 Offices, malls, hospitals

2. Industrial Facilities
🏭 Factories, production halls

3. Large Residential Complexes

🏢 High-rise apartments and condominiums

✅ Benefits

🌿 Improved Indoor Air Quality – Removes dust, allergens, VOCs

💡 Energy Efficiency – Can integrate with heat recovery and smart controls

🔧 System Flexibility – Modular design supports tailored applications

What is the difference between primary and secondary pumps in

chilled water systems? And when should each system be used?

In central cooling systems, especially in large and complex projects, the Primary-
Secondary Pumping System design is used for higher efficiency and better control.
But what is the difference between primary and secondary pumps? And when should we
use this system instead of the simpler Primary-Only system?

Primary Pumps – Primary Pumps:

Function: Circulate chilled water through the chiller evaporator.

Circuit: Operates in a closed circuit between the chiller and the decoupler line
(separation line), and does not serve the loads (AHUs/FCUs).

Flow: Constant flow in conventional systems.

Control: Not affected by changes in building loads.

Secondary Pumps – Secondary Pumps:

Function: Circulate chilled water to the loads inside the building (e.g. Air Handling Units
– AHUs).

Circuit: Operates in a separate circuit from the primary loop and is connected directly to
the loads.

Flow: Variable flow depending on the load, using VFDs.

Control: Controls pressure difference and water flow based on the actual building load.

Decoupler Line:

A pipe that connects the two circuits (primary and secondary) and acts as a hydraulic
separator, ensuring that one circuit does not affect the other.
When to choose each system?

Your choice between using a Primary-Only system or a Primary-Secondary system in the

cooling design depends on the project size, complexity, number of chillers, and required
load capacity. Let me show you when to use each system:

Primary-Only System (Single Loop):

Use it in the following cases:

Small or medium-scale projects.

When you have one or two chillers.

The building load is constant or does not vary significantly.

When you want to simplify the system and reduce costs.

Characteristics:
The same pump serves both chillers and loads.
Simpler to install and operate.
Less expensive.
Limited control and flexibility.
Primary-Secondary System:

Use it in the following cases:

Large-scale projects such as hospitals, malls, or towers.

When you have multiple chillers.

The load varies continuously (Variable Load).

When you need precise control of water flow based on the load.

To save energy by using VFDs on secondary pumps.

Characteristics:
Separates the chiller circuit from the load circuit.
Each circuit has independent pumps.
Flexible operation and maintenance (you can shut down a chiller or pump without
affecting the entire system).
Better control over system efficiency.

A 4-pipe fan coil unit (FCU) is an HVAC device that provides both heating and cooling to
a space by circulating hot and cold water through separate coils within the unit. Unlike
2-pipe systems that switch between heating and cooling, 4-pipe FCUs can provide both
simultaneously, offering greater flexibility and potentially higher efficiency.
Here's a more detailed explanation:
Key Features of a 4-Pipe FCU:
Independent Heating and Cooling:
A 4-pipe FCU has two separate water circuits: one for chilled water (cooling) and one for
hot water (heating).
Simultaneous Heating and Cooling:
This allows for different zones in a building to be heated and cooled at the same time,
catering to varying occupant preferences or load requirements.
No Changeover Required:
Unlike 2-pipe systems, 4-pipe FCUs don't need a changeover sensor to switch between
heating and cooling modes, as both hot and chilled water are available at all times.
Types of 4-Pipe FCUs:
4-pipe fan coil units come in various configurations, including floor-standing, ceiling-
mounted (both exposed and concealed), and wall-mounted.
Potential for Energy Efficiency:
By allowing for simultaneous heating and cooling, 4-pipe systems can potentially
optimize energy usage, especially in buildings with diverse thermal loads.
Improved Comfort:
4-pipe FCUs can offer more precise temperature control and potentially better indoor air
quality due to the ability to dehumidify while cooling.
In contrast to 2-pipe FCUs:
2-pipe FCUs have a single set of pipes (supply and return) for either hot or cold water,
 requiring a changeover to switch between heating and cooling.
2-pipe systems can only provide heating or cooling at any given time, not both
simultaneously.
4-pipe systems are generally more flexible and efficient in buildings with diverse
heating and cooling needs.

📅 How to Learn 3 Years’ Knowledge in 6 Months

Week Focus Area Description Resources
Understand refrigeration
YouTube (e.g., Danfoss,
1–2 HVAC Basics cycle, chillers, AHUs, FCUs,
Carrier), SkillCat app
pumps, valves
Manufacturer manuals (Carrier,
HVAC Operation & PM schedules, RCA, CM,
3–4 AERMEC), Simutech
Maintenance descaling, logs, safety
Multimedia
HVAC Controls & Sensors, actuators, VFDs, HVAC School Podcast, Johnson
5–6
Troubleshooting pressure/flow issues Controls videos
Architecture, protocols
Schneider Electric, Honeywell
7–8 BMS Basics (BACnet, Modbus), alarms,
BMS demos
integration
Electrical + plumbing basics, AutoCAD MEP tutorials,
9–10 MEP Coordination
MEP drawings, BOQs LinkedIn Learning
Load handling, ATS, Cummins/Perkins manuals,
11–12 Generators
maintenance, fuel system YouTube (RealPars)
Prepare sample logs, PM
Templates + real-life examples
13–14 Project Simulation sheets, RCA reports, daily
(I can help)
checklists
Mock Interviews + ChatGPT mock interviews +
15–16 Case studies + Interview Q&A
Real Project Study online HVAC forums