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Lecture 30 HVAC Interview Question Part 1 (HVAC Course in Hindi)

1) What are different types of HVAC System?

HVAC is a short form of Heating, Ventilation and Air Conditioning which purpose is to making the indoor environment habitable comfortable.

HVAC system are four types:-

  1. Split Heating and Air Conditioning System
  2. Hybrid Heat split system
  3. Ductable split heating and air condition system
  4. Packaged Heating and AC system

2) What are its limitation?

  1. Required skill for load calculation and installation
  2. Cost
  3. Energy Consumption
  4. Required high skill and knowledge for economically installation

3) Application of HVAC

  1. Residence
  2. Commercial industry
  3. Hospitality (Super Specialist)
  4. Research Center
  5. Space Research Center
  6. Chemical industry
  7. Food preservation etc

4) What is positive and negative pressure?

:- When your heating, cooling and ventilation system is poorly designed for the space or just not work properly. you can end up with positive or negative air pressure.

If you have a positive pressure problem, the air pressure inside your space is too high and air is being forced out. This pressure can cause doors opening outward to fly open themselves, potentially harming people.It is also means that your expansive cooled air is being wasted as it escape through every tiny opening.

:- In a negative pressure situation, the air pressure inside your space is lower than outside. The pressure difference caused air from outside the space to be sucked in due to which you feel traped in room. For room door open inward it required strength to open.

Due to these, Energy bill is high.

How exactly does air pressure get out of balance

  1. Hot air rising
  2. fan motor speed
  3. Exhaust fan
  4. Leaky ducts

5) Where negative pressure should be maintained and why?

Negative room pressure is an isolation technique used in hospitals and medicals centers to prevent cross-contamination from room to room. It includes a ventilation system that generates negative pressure to allow air to flow into the isolation room but not escape from the room.

For Isolation Negative pressure room:-

  1. Min of 12 air change per hour.
  2. Doors should be self closing
  3. Room should be well sealed
  4. The negative pressure should be exceed the supply by about 30%
  5. The Bathroom should be negative pressure.
  6. Exhaust from isolation room should be at least 25 feet from other ventilation intake.
  7. The exhaust duct should be over sized to allow loss of efficiency.

6)How to calculate duct size?

For Duct Size, We used ductulator or duct size softwares.

Firstly, there are two method of duct sizing

  1. Velocity Reduction Method (VRM) or Constant Velocity method
  2. Friction loss method (FLM) or Equal friction method

For Velocity Reduction method (VRM) we need two entity to calculate the duct sizing. a) Volume (CFM: Cubic feet per minute) b) Velocity (FPM: Feet per minute)

For Friction loss method (FLM) we need two entity to calculate the duct size a) Volume (CFM: Cubic feet per minute) b) Friction loss

7) What is Ventilation?

Ventilation is the method of introducing fresh air in space and removing old air from a conditioning space.

Process of supply fresh air and removing foul air is called ventilation.

APPLICATION:-

  1. Car Parking
  2. Kitchen
  3. Toilet

Ventilation can be achieved by two methods:-

  1. Forced (Mechanical) Ventilation
  2. Natural Ventilation

8) Where we do need fresh air, is it mandatory?

We need fresh air where the foul air is large like underground basement, kitchen etc where contamination like CO2 large and required fresh air to dilute.

9) What is local comfort cooling system?

This may be integrated with HVAC provided by a single system. for example AHU (Air Handling Unit) connected to duct work or they may be a combination of separate system for example mechanical ventilation but with radiator for heating and local comfort cooling unit.

Local comfort cooling system (split air conditioning system), It has two unit indoor unit & outdoor unit.

10) What is Centralized Air system?

Like All Air System

HVAC Interview Question

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