Chapter 1 - Fundamentals of Cooling Systems
Chapter 1 - Fundamentals of Cooling Systems
Chapter 1 - Fundamentals of Cooling Systems
Fundamentals and
BMS Controls
- Udemy Edition
www.ecobiru.com
HVAC Fundamentals and BMS Controls
Table Of Contents
www.ecobiru.com - Page 1
HVAC Fundamentals and BMS Controls
https://www.udemy.com/course/hvac-fundamentals/
This book is exclusive for those who have enrolled in the course; kindly
refrain from sharing it.
This book covers the four main topics of the course supplemented by a
variety of additional resources, including:
Should you need any further materials that could aid your learning, or if you
have any questions related to the course, feel free to send me a message at:
https://www.ecobiru.com/contact
Together, let's embark on this journey of discovery and mastery in HVAC and
BMS controls!
www.ecobiru.com - Page 2
HVAC Fundamentals and BMS Controls
01
F un da ment a ls
of C ooling
S ystems
www.ecobiru.com - Page 3
HVAC Fundamentals and BMS Controls
om
thermodynamics. The Laws of Thermodynamics are fundamental principles
governing energy and heat interactions
.c
The rst law of thermodynamics is a fundamental principle of physics that
states that energy cannot be created or destroyed, only transferred or
transformed from one form to another. In other words, the total energy of an
ru
isolated system remains constant. This law is also known as the principle of
conservation of energy.
bi
co
.e
w
w
w
www.ecobiru.com - Page 4
HVAC Fundamentals and BMS Controls
The second law of thermodynamics asserts that heat naturally moves from a
warmer object to a cooler one, but it doesn't ow naturally from a cooler
object to a warmer one. To reverse this heat transfer, external work is
required. In a vapor compression cycle, this is achieved by using a
compressor.
om
.c
ru
bi
co
.e
w
www.ecobiru.com - Page 5
HVAC Fundamentals and BMS Controls
om
radiation.
The air conditioning system is e ectively removing heat from the indoor air
.c
and releasing it outdoors, thereby cooling the indoor environment. This cycle
repeats continuously to maintain the desired indoor temperature. Heat
transfer happens at di erent heat exchangers located within various parts of
the air conditioning system.
refrigerant to absorb heat from one place and release it to another. This cycle
is used in air conditioners, refrigerators, and freezers. The vapor compression
.e
www.ecobiru.com - Page 6
HVAC Fundamentals and BMS Controls
The refrigeration cycle consists of four main components:
om
is then circulated to the condenser.
Condenser The condenser is a heat exchanger that removes heat
from the refrigerant gas. As the refrigerant gas passes
through the condenser, it cools down and condenses into
.c
a liquid.
Expansion valve The expansion valve is a device that reduces the
pressure of the refrigerant liquid. This sudden drop in
ru
pressure causes the refrigerant liquid to evaporate into a
gas.
bi
Evaporator The evaporator is another heat exchanger that absorbs
co
www.ecobiru.com - Page 7
HVAC Fundamentals and BMS Controls
om
.c
ru
bi
co
The refrigeration cycle relies on the change of phase of the refrigerant. In the
.e
evaporator, the refrigerant liquid evaporates into a gas, absorbing heat in the
process. This is because the latent heat of vaporization of the refrigerant is
much higher than its sensible heat. This means that it takes more heat to
w
change the refrigerant from a liquid to a gas than it does to raise the
temperature of the refrigerant by the same amount.
w
w
www.ecobiru.com - Page 8
HVAC Fundamentals and BMS Controls
Refrigerant
In the vapor compression cycle, the refrigerant serves as the working uid.
It's a uid that cycles between liquid and vapor states during the process. For
e ective operation in the vapor compression cycle, refrigerants must
om
possess certain critical characteristics to function e ectively:
.c
large amount of heat while evaporating, which helps in e cient cooling.
Low Boiling Point: A lower boiling point allows the refrigerant to
evaporate at lower temperatures, making it e ective in absorbing heat
from the environment.
into three regions: the liquid region, the vapor region, and the two-phase
region.
The liquid region is the region where the refrigerant is in a liquid state.
w
The vapor region is the region where the refrigerant is in a vapor state.
w
www.ecobiru.com - Page 9
HVAC Fundamentals and BMS Controls
om
.c
ru
bi
co
www.ecobiru.com - Page 10
HVAC Fundamentals and BMS Controls
om
Point 2: The compressor outlet
Point 3: The condenser outlet
Point 4: The evaporator inlet
.c
The four processes of the vapour compression cycle:
ru
Heat rejection: The process from point 2 to point 3.
Expansion: The process from point 3 to point 4
bi
Heat absorption: The process from point 4 to point 1.
co
.e
w
w
w
www.ecobiru.com - Page 11
HVAC Fundamentals and BMS Controls
om
refrigerant during an evaporation process can be calculated by nding
the di erence in enthalpy between the evaporator inlet (4) and
compressor inlet (1) on the Ph diagram.
.c
Heat rejected: The amount of heat rejected by a refrigerant per unit
mass during a condensation process can be calculated by nding the
di erence in enthalpy between the compressor outlet (2) and condenser
ru
outlet (3) on the Ph diagram.
Work done: The amount of work done per unit mass by a compressor
bi
can be calculated by nding the di erence in enthalpy between the
compressor inlet (1) and compressor outlet (2) on the Ph diagram.
co
.e
on P-h Diagram
www.ecobiru.com - Page 12
HVAC Fundamentals and BMS Controls
om
02
.c
ru
B uil d ing
bi
C ooling L o ad
co
a n d C hiller
.e
E ffi c ien c y
w
w
w
www.ecobiru.com - Page 13
HVAC Fundamentals and BMS Controls
om
DX systems are the most common type of air conditioning system used in
residential buildings. They use refrigerant to cool the air directly and the
condenser is usually air cooled. They typically serve a smaller area compared
.c
to chilled water system.
ru
Unitary systems: These are the most common type of DX system. They
bi
are typically used in homes and small o ces.
Single-split systems: These systems have one indoor unit (FCU) and one
co
indoor units.
Advantages of DX Systems
w
Simple setup
Easy to install and maintain
w
Relatively inexpensive
w
www.ecobiru.com - Page 14
HVAC Fundamentals and BMS Controls
Disadvantages of DX Systems
om
.c
ru
bi
co
www.ecobiru.com - Page 15
HVAC Fundamentals and BMS Controls
om
A chilled water system consists of the following components:
.c
Chiller The chiller is the heart of the chilled water system. It is
the component that cools down the water. There are two
main types of chillers, water cooled chiller and air cooled
chiller.
ru
Cooling tower The cooling tower is used to reject heat from condenser
water. This is done by evaporating water into the air.
bi
Chilled water The chilled water pumps are used to circulate chilled
co
Cooling coils Cooling coils are located in the air handling units (AHUs)
and fan coil units (FCUs). They are used to transfer heat
from the air to the chilled water.
w
w
w
www.ecobiru.com - Page 16
HVAC Fundamentals and BMS Controls
om
.c
ru
bi
Figure 2.2: Air-cooled (L) and Water-cooled (R) chilled water system schematic
co
.e
w
w
w
www.ecobiru.com - Page 17
HVAC Fundamentals and BMS Controls
om
that can a ect the cooling load, such as the size of the space, the number of
occupants, the type of equipment, and the outside temperature.
.c
There are a number of ways to calculate the cooling load. One common
method is to use a rule of thumb. For example, you can estimate that a 100-
square-foot o ce will require about 1 ton of cooling.
ru
Another way to calculate the cooling load based on sensor readings in the
bi
Building Management System. The formula to determine building load is:
co
Cooling load: Q =m × c × ∆T
Heat Balance
.e
www.ecobiru.com - Page 18
HVAC Fundamentals and BMS Controls
om
COP (Coe cient of Performance): COP is a measure of how much cooling is
produced for a given amount of energy input. It is calculated by dividing the
cooling output by the power input.
.c
COP = Cooling Output (kW) / Power Input (kW)
ru
kW/Ton: kW/Ton is a measure of how much power is required to produce
one ton of cooling. It is calculated by dividing the power input by the cooling
bi
output.
co
www.ecobiru.com - Page 19
HVAC Fundamentals and BMS Controls
om
03
.c
ru
B uil d ing
bi
Ma n a gement
co
S ystem
.e
C ontrols
w
w
w
www.ecobiru.com - Page 20
HVAC Fundamentals and BMS Controls
om
Air Handling Units (AHUs)
An air handling unit (AHU) is a large, packaged device that conditions and
distributes air throughout a building. It is typically located in a mechanical
.c
room or rooftop and consists of several components, including:
A fan: The fan is responsible for moving air through the AHU.
ru
A cooling coil: The cooling coil is where the air is cooled by chilled water.
A heating coil (for cold climate area): The heating coil is where the air is
bi
heated by hot water or steam.
A lter: The lter removes dust and other particulates from the air.
co
Constant air volume (CAV): CAV AHUs supply a constant amount of air to
each space, regardless of the load.
Variable air volume (VAV): VAV AHUs modulate the amount of air
w
www.ecobiru.com - Page 21
HVAC Fundamentals and BMS Controls
om
.c
ru
Figure 3.1: Typical Air Handling Unit
bi
Fan Coil Units (FCUs)
co
A fan coil unit (FCU) is a smaller, self-contained device that conditions air in a
single space. It typically consists of the following components:
.e
A fan: The fan is responsible for moving air through the FCU.
A cooling coil: The cooling coil is where the air is cooled by chilled water.
A heating coil: The heating coil is where the air is heated by hot water or
w
steam.
A lter: The lter removes dust and other particulates from the air.
w
w
www.ecobiru.com - Page 22
HVAC Fundamentals and BMS Controls
om
Size Large Small
.c
Location Mechanical room or rooftop Ceiling or wall
lter ru
Components Fan, cooling coil, heating coil, Fan, cooling coil, heating coil,
lter
bi
Air Centralized Decentralized
co
conditioning
.e
www.ecobiru.com - Page 23
HVAC Fundamentals and BMS Controls
Air-side controls
There are four main types of AHU control loops:
om
Static pressure control
CO2 control
Supply air temperature control
.c
Every control loop comprises three key components: a set point, a sensor,
and an output mechanism. The set point represents the target value for the
parameter being controlled. The sensor's role is to gauge the current value
ru
of this parameter. Lastly, the output device acts to modify the system in
order to reach the desired set point.
bi
Space Temperature Control
co
www.ecobiru.com - Page 24
HVAC Fundamentals and BMS Controls
om
The output device for static pressure control is a variable speed drive
(VSD) that controls the speed of the fan.
.c
CO2 Control
CO2 control is used to reduce the amount of fresh air into the space.
The set point for CO2 control is typically 700 to 1,000 ppm.
ru
The sensor for CO2 control is a CO2 sensor.
The output device for CO2 control is a damper that controls the amount
bi
of fresh air into the space.
co
www.ecobiru.com - Page 25
HVAC Fundamentals and BMS Controls
om
Constant Primary Flow
Constant Primary, Variable Secondary Flow
Variable Primary Flow
.c
Constant Primary Flow
In a constant primary ow system, the pump is always running at the
same speed. This means that the ow rate is always the same,
regardless of the load. ru
Constant primary ow systems are simple and inexpensive to operate,
bi
but they can be ine cient. This is because the pump is always running at
co
www.ecobiru.com - Page 26
HVAC Fundamentals and BMS Controls
om
adjusted to meet the load.
Constant primary, variable secondary ow systems are more e cient
than constant primary ow systems, because the secondary pump can
.c
be slowed down when the load is low.
Constant primary, variable secondary ow systems are common in large
buildings or in buildings where the load changes throughout the day.
ru
bi
co
.e
w
w
w
www.ecobiru.com - Page 27
HVAC Fundamentals and BMS Controls
om
piping system, but they can also be the most complex.
Variable primary ow systems are becoming increasingly common in
new buildings.
.c
ru
bi
co
.e
www.ecobiru.com - Page 28
HVAC Fundamentals and BMS Controls
om
adjust the ow rate to the individual AHUs.
In a constant primary, variable secondary ow system, the controls are
more complex. The pump speed must be controlled to maintain the
.c
desired ow rate to the secondary pump. The valves are used to adjust
the ow rate to the individual AHUs.
In a variable primary ow system, the controls are the most complex.
ru
The pump speed must be controlled to maintain the desired ow rate to
the chillers. The valves are used to adjust the ow rate to the individual
bi
AHUs.
co
Chiller Sequencing
Chiller sequencing is the process of starting and stopping chillers in an
.e
www.ecobiru.com - Page 29
HVAC Fundamentals and BMS Controls
The general rule of thumb for chiller sequencing is to start the chillers in the
following order:
om
3. Chilled water pump
4. Chiller
.c
ru
bi
co
If you have more than one chiller, you can use a lead-lag sequence to start
and stop the chillers. The lead chiller is the rst chiller to start, and the lag
chiller is the last chiller to start. The lead-lag sequence is used to evenly
.e
chiller staging:
w
www.ecobiru.com - Page 30
HVAC Fundamentals and BMS Controls
om
capacity.
.c
The chilled water return temperature method is a less accurate method of
chiller staging than the building cooling load calculation method. However, it
is also a less complex method. The BMS will monitor the chilled water return
ru
temperature and start and stop the chillers based on this temperature.
bi
Chilled Water Flow Rate
The chilled water ow rate method is the least accurate method of chiller
co
staging. However, it is also the simplest method. The BMS will monitor the
chilled water ow rate and start and stop the chillers based on this ow rate.
.e
w
w
w
www.ecobiru.com - Page 31
HVAC Fundamentals and BMS Controls
om
04
.c
ru
E nerg y
bi
E ffi c ien c y
co
I mprovement
.e
w
w
w
www.ecobiru.com - Page 32
HVAC Fundamentals and BMS Controls
om
over the course of a day. This pro le plays a crucial role in selecting and
sizing chillers. Without understanding the load pro le, determining the
appropriate size of the chiller to install or the duration for which a speci c
.c
chiller should operate becomes unclear.
ru
A typical load pro le for an o ce building would be low during the o -
peak hours (midnight to 7 am) and high during the peak hours (8 am to 5
bi
pm).
A typical load pro le for a shopping center would be similar to an o ce
co
www.ecobiru.com - Page 33
HVAC Fundamentals and BMS Controls
om
1. Determine the operating schedule for each con guration.
2. Calculate the power consumption for each chiller during each operating
period, based on the e ciency of the chiller operating at the load.
.c
3. Calculate the energy consumption for each chiller during each operating
period by multiplying the operating duration.
4. Sum the energy consumption for all chillers during each operating
ru
period to get the daily consumption.
5. Compare the total energy consumption for each con guration in either
bi
daily, weekly or annual basis.
temperature, the lower the condensing pressure, and the higher the
chiller e ciency.
w
w
www.ecobiru.com - Page 34
HVAC Fundamentals and BMS Controls
om
Pump and Fan System
Reduce losses: Minimize minor losses by using larger pipes, minimizing
.c
piping length, and reducing sharp bends.
Avoid oversizing pumps and fans: Use a valve to reduce ow rate
instead of oversizing the pump or fan.
Absorption Chiller ru
bi
Absorption chiller uses a heat source to supply the energy required for the
cooling process. It is versatile, capable of utilizing various heat sources like
co
waste heat, solar energy, or burning gases. Owing to the lack of moving
parts, it is more reliable and operates more quietly compared to vapor
.e
www.ecobiru.com - Page 35
HVAC Fundamentals and BMS Controls
om
Lower COP (coe cient of performance) compared to vapor compression
chillers, meaning more heat is required to produce the same amount of
cooling.
.c
Overall, absorption chillers are a viable option for applications where waste
heat is available and there is no need for a high COP.
ru
bi
co
.e
w
w
w
www.ecobiru.com - Page 36
HVAC Fundamentals and BMS Controls
05
Appendix:
www.ecobiru.com - Page 37
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 38
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 39
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 40
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 41
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 42
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 43
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 44
HVAC Fundamentals and BMS Controls
www.ecobiru.com - Page 45
HVAC Fundamentals and BMS Controls
Endnotes
As we reach the end of this journey through 'HVAC Fundamentals and BMS
Controls - Udemy Edition', we hope it has been an enlightening and valuable
experience for you. Your insights and opinions are incredibly important to us.
We would be grateful if you could take a few moments to share your
thoughts and feedback on this book. Your input not only helps us understand
your experience as a reader but also guides me in enhancing and improving
future editions.
Please feel free to reach out with your comments, suggestions, or questions
at:
https://www.ecobiru.com/contact
Thank you for your time, and I look forward to hearing from you!
www.ecobiru.com - Page 46