This document discusses heating, ventilation, and air conditioning (HVAC) systems. It begins by explaining how HVAC principles influence architectural design. It then provides descriptions of common HVAC components and systems, including air handlers, makeup air units, rooftop units, fan coil units, constant air volume systems, and variable air volume systems. The document also discusses heating systems such as fireplaces, stoves, heat pumps, solar heating, and portable units. It covers ventilation methods and factors like indoor air quality. Finally, it addresses HVAC energy efficiency considerations for heating, air conditioning, and thermodynamics.

1. Heating , ventilating and air
conditioning

2. Objectives :
1. Recognize the significance of HVAC in the total
function of a building
2. Explain how HVAC principles influence an
architect’s overall design.

3. Introduction
Le Corbusier, one of the great masters of the 20th century
architecture, turned to more integral architectural ways to
control the environment than employing elaborate air conditioning
system which could not always be relied upon.
His contemporary, Meis van de Rohe, never felt so compelled,
and retained pure glazed forms and their dependence on
extensive mechanical systems.
In 1948, when Meis designed the Lake Shore Apartments in
Chicago, he was able to have the all-glass wall he had dreamt of
since 1990, but the air-conditioning equipment originally
specified was deleted to reduce building costs.

4. In 1954, with the help of an elaborate cooling apparatus atop his
Seagram Building, Meis was able to achieve the sealed box that Le
Corbusier had attempted in the Salvation Army Building.
By the time the Seagram Building was designed, mechanical
systems for vertical transportation, lighting, heating, and cooling
were consuming more than half of the budgets of new buildings. It
was as if the building now was the mechanical system, wrapped in a
membrane

5. Description
HVAC is an acronym that stands for "heating, ventilating, and air
conditioning". This is sometimes referred to as climate control. In
certain regions the term "Building Services" is also used, but may
also include plumbing and electrical systems. Refrigeration is
sometimes added to the field's abbreviation as HVAC&R or HVACR.
The HVAC seek s to provide:
thermal comfort, acceptable indoor air quality, reasonable
installation, operation, and maintenance costs, provide ventilation ,
reduce infiltration, maintain pressure relationships between spaces

6. Terms
Air handler, or air handling unit (AHU)
can mean a whole unit including the blower, heating and cooling
elements, filter racks or chamber, dampers, humidifier, and other central
equipment in direct contact with the airflow. This does not include the
ductwork through the building.
Makeup Air Unit (MAU)
is an air handler that conditions 100% outside air. MAUs are typically
used in industrial settings, or in once-through, low-flow, or primary-
secondary commercial HVAC systems.
Rooftop Unit (RTU)
is an air handling unit, of recirculating or once-through design, that is
for outdoor installation. They most often include, internally, their own
heating and cooling
devices. RTUs are very popular -- particularly for single-story commercial
buildings.

7. Fan Coil Unit (FCU)
is a small terminal unit that is often composed of only a blower and
either a heating or a cooling coil. Often used in hotels, condos, or
apartments.
Constant Air Volume (CAV)
is an all-air or air-water HVAC system that has variable supply air
temperature, but a constant flow rate of air. Most residential forced-air
systems are small CAV systems with on/off control.
Variable Air Volume (VAV)
is an all-air or air-water HVAC system that has a relatively fixed supply air
temperature, but the volumetric flow rate of air varies to meet the thermal
load. Most new commercial buildings have VAV systems due to their
reduced fan energy consumption, as compared to CAV. contractor
expects will have similar thermal loads. Zones are defined to reduce
the number of HVAC subsystems, and thus initial cost. Small
residences typically have only one conditioned thermal zone, plus
unconditioned spaces such as attached garages, attics, and
crawlspaces. Basements may be either conditioned or
unconditioned.

8. Heating Systems
Heating systems may be classified as central or local.
Central heating is often used in cold climates to heat private houses and
public buildings. Such a system contains a boiler, furnace, or heat pump to
heat water, steam, or air, all in a central location such as a furnace room in a
home or a mechanical room in a large building.
The system also contains piping or ductwork to distribute the heated
fluid, and radiators to transfer this heat to the air. The term radiator in
this context is misleading since most heat transfer from the heat exchanger is
by convection, not radiation. The radiators may be mounted on walls or
buried in the floor to give under-floor heating.

9. 1. Fireplace
The fireplace was developed as a method of heating rooms by means of an
open fire. The first fireplaces were hearths, recessed into the walls of
buildings, with short flues that communicated with the open air. The useful
heat given off by a fireplace consists of both direct radiation from the
burning fuel and indirect radiation from the hot sidewalls and back wall.
2. Stoves
The stove, an enclosure of metal or ceramic materials in which fuel is
burned, is an improvement over the fireplace because its surfaces are in
contact with the air of the room and by convection deliver heat to the air
passing over them.
The heat can be provided from electric coils or strips used in varying
patterns—for example, convectors in or on the walls, under windows, or
as baseboard radiation in part or all of a room.

10. 4. Heat Pump
A heat pump is a system designed to provide useful heating and
cooling, and its actions are essentially the same for either process.
Instead of creating heat, as does a furnace, the heat pump
transfers heat from one place to another. In heating season, a
liquid refrigerant, such as Freon, is pumped through a coil that is
outside the area to be heated.
5. Solar Heating
During each sunlight hour of the day approximately 0.9 kw per sq m
(280 Btu per hour per sq ft) of solar energy reaches the surface of
the earth. The actual energy received varies with time of day, time
of year, latitude, clarity of the atmosphere, and the direction
relative to the sun that an absorbing surface faces at any given
time. This energy can often be more than enough to heat a well-
designed building, provided enough solar absorbing surface can
be installed and enough heat storage is made available to carry the
building during periods of darkness and inclement weather. A
common method employed uses roof panels with
built-in water circuits.

11. 6. Portable Heating Units
Houses lacking central-heating systems are equipped with various types of
portable and semi portable heating devices, many of which can be moved
from room to room as needed. The most common types are kerosene
stoves and electric heaters.
Ventilation
Buildings in which people live and work must be ventilated to replenish
oxygen, dilute the concentration of carbon dioxide and water vapor, and
minimize unpleasant odors.
A certain amount of air movement or ventilation ordinarily is provided by
air leakage through small crevices in the building's walls, especially around
windows and doors. Such haphazard ventilation may suffice for homes, but
not for public buildings such as offices and theaters, or for factories.
Engineers estimate that for adequate ventilation the air in a room should be
changed completely from one and a half to three times each hour, or
that about 280 to 850 liters (about 10 to 30 cu ft) of outside air per
minute should be supplied for each occupant. Providing this amount of
ventilation usually requires mechanical devices to augment the natural
flow of air.

12. Simple ventilation devices include fans or blowers that are
arranged either to exhaust the stale air from the
building or to force fresh air into the building, or
both.
Ventilating systems may be combined with heaters, filters,
humidity controls, or cooling devices. Many systems include
heat exchangers. These use outgoing air to heat or cool
incoming air, thereby increasing the efficiency of the system
by reducing the amount of energy needed to operate it.
Ventilation is the changing of air in any space to remove:
moisture, odors, smoke, heat, airborne bacteria. Ventilation
includes both the exchange of air to the outside as well
as circulation of air within the building. It is one of the most
important factors for maintaining acceptable indoor air quality
in buildings

13. Methods for ventilating a building
A. Mechanical or Forced ventilation
used to control indoor air quality. Excess humidity, odors, and
contaminants can often be controlled via dilution or replacement
with outside air. But in humid climates, much energy is required to
remove excess moisture from ventilation air.
Kitchens and bathrooms typically have mechanical exhaust to
control odors and sometimes humidity. Factors in the design of
such systems include the flow rate (which is a function of the fan
speed and exhaust vent size) and noise level. If the ducting for the
fans traverse unheated space (e.g., an attic), the ducting should
be insulated as well to prevent condensation on the ducting.
Direct drive fans are available for many applications, and can
reduce maintenance needs.

14. B. Natural ventilation
HVAC Energy Efficiency
Heating Energy
Water heating is more efficient for heating buildings and was the
standard many years ago. Today forced air systems can double for air
conditioning and are more popular. The most efficient central heating
method is geothermal heating.
Air Conditioning Energy
The performance of vapor compression refrigeration cycles is limited by
thermodynamics. These AC and heat pump devices move heat rather
than convert it from one form to another, so thermal efficiencies do not
appropriately describe their performance.
Theoretically, an air-conditioning system consists of centralized
equipment that provides an atmosphere with controlled temperature,
humidity, and purity at all times, regardless of weather conditions.

15. Centralized air-conditioning systems, providing fully controlled
heating, cooling, and ventilation, as required, are employed
widely in theaters, stores, restaurants, and other public
buildings. Such systems, being complex, generally must be
installed when the building is constructed; in recent years,
these systems have increasingly been automated by computer
technology for purposes of energy conservation.
The design of an air-conditioning system depends
on:
the type of structure in which the system is to be placed,
the amount of space to be cooled, the number of
occupants, and the nature of their activity.

16. Air-conditioning
An air conditioning system, or a stand-alone air conditioner, provides
heating, cooling, ventilation, and humidity control for all or part of a
building.
'Central', 'all-air' air
conditioning systems are often installed in modern residences,
offices, and public buildings, but are difficult to retrofit (install in a
building that was not designed to receive it) because of the bulky air
ducts required. A duct system must be carefully maintained to
prevent the growth of pathogenic bacteria in the ducts.
An alternative to large ducts to carry the needed air to heat or cool
an area is the use of remote fan coils or split systems. These
systems, although most often seen in residential applications, are
gaining popularity in small commercial buildings. The remote coil is
connected to a remote condenser unit using piping instead of ducts.

17. A dehumidifier is an air-conditioner-like device that
controls the humidity of a room or building. They are often
employed in basements which have a higher relative humidity
because of their lower temperature (and propensity for damp
floors and walls). In food retailing establishments, large open
chiller cabinets are highly effective at dehumidifying the
internal air. Conversely, a humidifier increases the humidity of
a building.
Air-conditioned buildings often have sealed windows,
because open windows would disrupt the attempts of the
HVAC system to maintain constant indoor air conditions.

18. Types
1. Central air conditioning units live entirely outside the building,
separate from the area to be cooled. Hot air is pumped out of the
house while cool air is distributed throughout the building by way of
ducts.
2. Split-systems have 2 separate components; the motor of the air
conditioning unit lives outside the building whilst the air outlet of the
system remains inside.
3. A Stand Alone/Portable type of air conditioner is a single movable unit
can be easily moved to whatever room needs to be cooled.
4. A Thru-Wall/Window air conditioner is a single unit mounted through a
wall or window. Part of it is inside the building and part sticks through to
the outside. with several speeds would have a broader range of options
like low, medium and high.

19. Max Cooling Capacity
Capacity is the principle gauge of how much cooling power an
air conditioner has, and is measured in British Thermal Units per
hour (BTU/hr). Room air conditioners range in
capacity from about 5000 BTU/hr to about 30,000 BTU/hr.
Air conditioner
An air conditioner (AC or A/C) is an appliance, system, or
mechanism designed to extract heat from an area using a
refrigeration cycle. The most common uses of modern
Air conditioners are for comfort cooling in buildings and
transportation vehicles.
A combined system that also provides heating and ventilation is
often called an HVAC system.

20. 1. Window and through-the-wall air conditioners
2. Portable air conditioners
A portable air conditioner or portable A/C is an air
conditioner on wheels that can be easily transported inside
a home or office. They are currently available with capacities
of about 6,000 to 14,000 BTU/h (1800 to 4100 watts
output) and with and without electric resistance heaters.
Portable air conditioners come in two forms, split and mono
block.
3. Mono block systems
These are vented to the outside via air ducts. A single duct
mono block unit draws air out of the room to cool its
condenser. This air is then replaced by hot air from outside
or other rooms, thus reducing efficiency.

21. 4. Central air conditioners
Central air conditioning, commonly referred to as central air
(US) or air-con (UK), is an air conditioning system which uses
ducts to distribute cooled and/or dehumidified air to typically
more than one room, or uses pipes to distribute chilled water
to heat exchangers.
•With a typical split system, the condenser and compressor
are located in an outdoor unit; the evaporator is mounted in the
air handling unit (which is often a forced air furnace).
•With a packaged system, all components are located in a
single outdoor unit that may be located on the ground or roof.

22. Central air conditioning has several benefits as compared to
having many smaller distributed units:
•When the air handling unit turns on, room air is drawn in from
various parts of the house through return-air ducts. This air is
pulled through a filter where airborne particles such as
dust and lint are removed.
Sophisticated filters may remove microscopic pollutants as
well. The filtered air is routed to air supply ductwork that
carries it back to rooms. Whenever the air conditioner is
running, this process repeats continually.
•Because the central air conditioning's condenser unit is
located outside the home, it typically offers a lower level of
noise indoors than window or through-the-wall air conditioning
units, for example. However, the air ducts do become dirty
over time, and pose a risk of growth and spread of harmful
microorganisms.

23. 5. "Ductless", "duct-free", or "mini-split" air
conditioners
Ductless mini-split air conditioners combine some traits of
central air conditioning systems with some traits of window or
through-the-wall units. They were invented as an alternative to
window air conditioners for buildings where the cool-air
distribution ducts of a central air conditioning system could not
be installed or would be prohibitively
expensive to install.
Evaporative coolers
In very dry climates, evaporative coolers are popular for
improving comfort during hot weather. The evaporative cooler is
a machine that draws or forces outside air through a wet pad.
The sensible heat of the incoming air is measured by a dry bulb
thermometer.
The total heat (sensible heat plus latent heat) of the entering air
is unchanged. Some of the

24. sensible heat of the entering air is converted to latent heat by the
evaporation of water in the wet cooler pads. If the entering air is dry
enough, the resulting supply air can be quite comfortable.
Absorption air coolers and washers
There is a process called absorptive refrigeration which uses heat to
produce cooling. In one instance, a three-stage absorptive cooler first
dehumidifies the air with a spray of saltwater or brine. The brine
somatically absorbs water vapor from the air. The second stage
sprays water in the air, cooling the air by evaporation.
Finally, to control the humidity, the air passes through another brine
spray.
Absorptive chillers
Some buildings use gas turbines to generate electricity. The exhausts of
these are hot enough to drive an absorptive chiller that produces cold
water. The cold water is then run through heat exchangers in air handlers
to provide cooling and dehumidification.
The dual use of the energy, both to generate electricity and cooling,
makes this cogeneration technology attractive when regional utility and
fuel prices are more expensive than average

25. Thermostats
Thermostats control the operation of HVAC systems, turning on
and off, or modulating, the heating or cooling systems to bring the
building to the set temperature. Thermostats may also be
incorporated into facility energy management systems in which the
electrical power utility customer may control the overall energy
expenditure. In addition, a growing number of electric utilities have
made available a device which, when professionally installed, will
control or limit the power to an HVAC system during peak use
times in order to avoid necessitating the use of rolling blackouts.
There are many widely used thermostat technologies such as
mechanical, electromechanical (EM), pneumatic, digital and hybrid.

26. Equipment capacity
Air conditioner equipment cooling capacity is described in
terms of "tons of refrigeration".
A "ton of refrigeration" is defined as the cooling power of
one short ton (2000 pounds or 907 kilograms) of ice
melting in a 24-hour period. This is equal to 12,000 BTU
per hour, or
3517 watts. Single-family residential "central air" systems
are usually from 2 to 5 tons (3 to 20 kW) in capacity