HVAC and Escalators Elevation

Introduction to HVAC

What is HVAC?

HVAC stands for Heating, Ventilating, and Air Conditioning. It's a system that provides:

Heating and cooling for residential, commercial, and industrial buildings.
Fresh outdoor air to dilute interior airborne contaminants like odors and volatile organic compounds (VOCs) emitted from interior furnishings and cleaning chemicals.
Three functions often combined into one system in modern homes and buildings.
Warmed, cooled, or dehumidified air flowing through tubes called ducts to be distributed to all the rooms.

Functions of HVAC Systems

To control temperature.
To control relative humidity.
To provide ventilation in closed areas.
To maintain required cleanliness in a specified area.

Applications of HVAC

Electronics Industry.
Food & beverage industry.
Pharmaceutical Industry.
Hotels, offices, and buildings for human comfort.
Aerospace engineering.

Requirements for HVAC

Consider:

Area.
Purpose.
Location.
Materials.
Occupants.
Heat exemption of area.
Human comfort.
Heavy machineries/gadgets.

Heating

Meaning: Increase room temperature.
Types: Forced Air and Radiant.
Equipments: Gas, electric, oil furnace; oil, gas boilers; heat pump.

Ventilation

Meaning: Reduce humidity, odors, smoke, heat, dust, bacteria, CO2.
Types: Natural, Mechanical.
Application: Kitchen, car-parking, tunnels, warehouses, basements, welding workshops.

Air Conditioning (AC)

Meaning: Reduce Temperature to comfort users.
Types: Comfort AC, Industrial AC
Equipments: Window AC, Split AC, Ductable AC, Chiller Package AC, Package AC, VAM (Variable Air Volume).
Application:
- Comfort AC: office, Bank, Cinema Halls, Hotels.
- Industrial AC: medical Equipment's, clean Hospitals, operating Rooms, Data centers etc.

Refrigeration

Use: Make ice, cool drinks, preserve food.
Types: Mechanical Refrigeration, Absorption Refrigeration, Evaporation cooling, Thermoelectric Refrigeration.
Equipment: Deep Freezers, Refrigerators, medical Ref., bottle (display) Coolers, cold storage plants, Ice candy plants, Transport Refrigerators etc.

Components of HVAC System

Chillers.
Air Handling Unit (AHU).
Ducting.
Risers.
Filters.
Dampers.
Chilling and Heating coils.
Sensors.
Temperature and RH controllers.

Components Details

Weather louvre: To prevent insects, leaves, dirt, and rain from entering.
Silencer: To reduce noise caused by air circulation.
Flow rate controller: Automated adjustment of volume of air (night and day, pressure control).
Control damper: Fixed adjustment of volume of air.
Heating unit: To heat the air to the proper temperature.
Cooling unit / dehumidifier: To cool the air to the required temperature & to remove moisture from the air.
Humidifier: To bring the air to the proper humidity if too low.
Filters: To eliminate particles of pre-determined dimensions and for microorganisms.

AHU Components

Centrifugal Fan.
Air Dampers (For Return Flow).
Heating coil.
Filters.
Cooling coil.
Humidifier.
Bag Filter.
Fresh Air Intake.
Outdoor Air mixing section.
Preheater
Reheat coil.

Factors affecting AC Systems

Window.
Door.
Opening of doors.
Number of people.
Machineries.
Space design.

Tests for HVAC System Validation

Number of air changes per hour.
Flow pattern test.
Relative humidity (RH) and temperature Rating.
Pressure balancing.
HEPA filter integrity test.

HVAC Goals

Control Temperature.
Fresh air circulation.
Air Filtration.
Energy Efficient / Economical: Variable air volume, digital conduct system, low-pressure design, reclaimed heat / cooling.

Types of AC System

Window AC
Split AC
Tower
Cassette
Floor and Tower
VRF (Variable Refrigerant Flow)
Package

Split AC System

A split system is a combination of an indoor air handling unit and an outdoor condensing unit.

Indoor Unit

Contains:

a fan.
an air-to-refrigerant heat exchanger (or cooling coil).
an expansion device.

Outdoor Unit

Consists of:

a compressor.
a condenser coil.

Split systems are typically found in residential or small commercial buildings.

Energy Efficiency

These systems have the highest energy efficiency rating (EER).
Manufacturers are required to take a step further and provide a seasonal energy efficiency rating (SEER) for use by consumers
More SEER rating, the more efficient the AC system operates.
If heating is required, an alternate method of heating the interior of the building must be used, usually in the form of electric or gas heating.

Air Conditioning (AC) Definition

Often referred to as AC, it is the process of altering the properties of air (primarily temperature and humidity) to more comfortable conditions.

Air conditioning is also done with the aim of distributing the conditioned air to an occupied space such as a building or a vehicle to improve thermal comfort and indoor air quality.

In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, cooling, dehumidification, cleaning, ventilation, or air movement).

However in construction, such a complete system of heating, ventilation, and air conditioning is referred to as heating, ventilation, and air conditioning (HVAC).

Central Air Conditioning

Central air conditioners circulate cool air through a system of supply and return ducts.
Supply ducts and registers, openings in the walls, floors, or ceilings covered by grilles, carry cooled air from the air-conditioner into the building.

The cooler air becomes warmer as it circulates through the home, then it flows back to the central air conditioner through return ducts.

Types of Centralized Systems

Centralized Ducted "All - Air System".
Centralized Fluid Based Hydronic System.
Combined (Hybrid) water and Air conditions system.

Characteristics, Advantages & Disadvantages

Service large area
longer Life.
Requires plant Room for placing of main air handling unit: more than 100 Tons of refrigeration capacity of Refrigeration.
Maintenance Required at plant Room only.
Less flexibility for future Expansion.
Better control & Quality of space temperature.
It can be integrated as part of Smoke control system.
Cooperation is required for controlling the wire handling unit.
Air Cleanliness is high because of installing medium or high efficiency air filters.
High system component Efficiency
Both Investment and operation Costs are higher.

Centralized Ducted Systems: Important Components

Air handling Unit: It is a cabinet that includes or houses the central furnace, air conditioner, or heat pump and the plenum and blower assembly that forces air through the ductwork.
Intake Louvers: These are the external louvers through which supply air is drawn into the building. Intake is generally equipped with a volume control damper to regulate the amount of fresh air and economizing the quantity of outside air during favorable Outside conditions.
Supply fans: These are used to circulate the air through the network of ductwork
Ductwork: It is a branching network of round or rectangular tubes generally constructed of sheet metal, fiberglass board, or a flexible plastic and wire composite material located within the walls, floors and ceilings. The three most common types of duct material used in home construction are metal, fiber-glass duct board, and flex-duct.
Filters: are used to remove particles of dust or dirt from the supply air.
Heating coils: These heat up the incoming air stream using coils through which hot water is passed or banks of electric heating elements.
Cooling coils: These cool the incoming air-stream using coils through which chilled water is passed.
Supply Ductwork: These carry air from the air handler to the rooms in a house. Typically each room has at least one supply duct and larger rooms may have several.
Return Duct work: These carry air from the conditioned space back to the air handler. Most houses have only one or two main return ducts located in a central area.
Supply and Return Plenums: are boxes made of duct board, metal, drywall or wood that distribute air to individual ducts or registers.
Terminal Reheat coils: use hot water coils or electric heating elements to heat up the air being supplied to one part of the building according to the temperature in that space.
Supply and Extract Grilles: are the points at which the air is either supplied into or extracted from the space, and may be ceiling mounted. Also called diffusers.
Boots: connects ductwork to registers.
Extract fans: are used to extract the air from the space and discharge it to outside
Return Air Ducts: are transition connections between inlet and outlet ductwork sections, which let a controlled amount of air re-circulate around the air conditioning system again when full fresh air is not required.
Exhaust Louvers: are the external louvers through which extracted air is discharged from the building.

AC Tonnage Calculation

As Per Room Volume

Given a room with dimensions:

Length (l) = 16 ft
Width (b) = 14 ft
Height (h) = 10 ft

Room Volume Calculation:

$Volume = l \times b \times h$

$Volume = 16 \times 14 \times 10 = 2240 \text{ cu.ft}$

Assuming standard window and door sizes:

Window = 2 (3'x4')
Door = 1 (2.5'x7')

AC Tonnage Estimation:

$\text{AC Tonnage} = \frac{\text{Volume of the room}}{1000}$

$\text{AC Tonnage} = \frac{2240}{1000} = 2.24 \text{ tons}$

As Per BTU Factor

Room Volume (as before): 2240 cu.ft

BTU (British Thermal Unit) Multiplying Factor: Assuming 6 BTU per cu.ft

$1 \text{ ton} = 12000 \text{ BTU}$

BTU Calculation:

$BTU = \text{Volume of the room} \times 6$

$BTU = 2240 \times 6 = 13440 \text{ BTU}$

BTU for Openings:

Number of doors = 1
Number of windows = 2
BTU of doors & windows ≈ 1000 BTU per opening

$BTU_{\text{openings}} = 2 \times 1000 = 2000 \text{ BTU}$

BTU for People:

Assuming 500 BTU per person. For 5 people:

$BTU_{\text{people}} = 5 \times 500 = 2500 \text{ BTU}$

Total BTU of the Room:

$BTU_{\text{total}} = \text{Volume} + \text{Openings} + \text{People}$

$BTU_{\text{total}} = 13440 + 2000 + 2500 = 17940 \text{ BTU}$

BTU to Tons Conversion:

$\text{Tons} = \frac{BTU_{\text{total}}}{12000}$

$\text{Tons} = \frac{17940}{12000} = 1.495 + 20\% = 1.794 \text{ Tons}$

Brands Mentioned:

Voltas
Daikin
Mitsubishi
General