Lecture 1: Introduction to HVAC - SatchNet Electronic Systems

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BUILDING MANAGEMENT SYSTEMS
(BMS)
THEORY & PRACTICE
Firas Obeido
Managing Partner, SatchNet

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COURSE OBJECTIVES:
Provide attendance with basic knowledge on
how to design, specify and check a BMS Control
System, DDC System and field devices to give
the best functions and maximum efficiency and
return on investment. (ROI)

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COURSE PROGRAM:
DAY ONE: (4 Hours)
Introduction.
Heating, Ventilation, Air-Conditioning & Refrigeration Systems.
Introduction to Control Systems & Control Loops.
Types of Control Systems.

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COURSE PROGRAM:
DAY TWO: (4 Hours)
Sensing Elements: Detectors, Transmitters & Sensors.
Final Control Elements: Actuators, Valves & Dampers.
Other Control Elements: Variable Speed Drives, Humidifiers,
Electric Heating Regulators.
Stand Alone HVAC Controllers.

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COURSE PROGRAM:
DAY THREE: (4 Hours)
Direct Digital Control Terminology (DDC).
DDC Hardware & Software.
Operator Machine Interface (OMI) : Built-In, Portable,
WorkStation.
Communication & Networking Devices.
Energy Saving Features through DDC’s.

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COURSE PROGRAM:
DAY FOUR: (4 Hours)
BMS System Design.
BMS System Applications.
BMS System Features.
Integration to Third Party Systems.
Future of BMS Systems.

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COURSE PROGRAM:
DAY FIVE: (4 Hours)
Practical Exercises.
Closing.

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INTRODUCTION

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• THE NEED FOR AUTOMATIC CONTROLS
• SAFTEY: TO ACHIEVE PLANT/ PROCESS SAFETY
OPERATION
• STABILITY: TO MAKE PLANT/ PROCESS WORK STEADILY
WITHOUT WORRYING FLUCTATIONS OR COSTLY
SHUTDOWNS
• ACCURACY: THE MORE PLANT/ PROCESS IS ACCURATE,
THE INCREASED QUALITY AND COMFORT OF WORKING
ENVIORENMENT. ( ECONOMIC SUCCESS )

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Heating, Ventilation,
Air-Conditioning &
Refrigeration Systems

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IT IS NOT WITHIN THE SCOPE OF THIS COURSE TO EXAMINE
IN DETAILS THE FACTORS INVOLVED IN THE DESIGN OF
HVAC SYSTEMS. THE INFORMATION IN THIS SECTION IS
INTENDED TO ASSIST IN UNDERSTANDING THOSE
PROCESSES WHICH ARE CONCERNED WITH AUTOMATIC
CONTROLS.

AIR CONDITIONING TERMS:
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Dry Bulb Temperature: The temperature of the air as indicated by an
ordinary thermometer.
Wet Bulb Temperature: The temperature indicated by a thermometer
where the bulb is covered by a wetted wick and exposed to a current of
rapidly moving air.
Dew Point Temperature: The temperature at which condensation of
moisture begins to form when air is cooled.
Moisture Content: The mass of water vapour per unit mass of dry air in
the mixture. This is usually expressed as Kg of moisture per Kg of dry air.

AIR CONDITIONING TERMS:
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Relative Humidity: The degree of saturation of air at a particular dry bulb
temperature. It is expressed as a percentage. At 100% RH the air is fully
saturated with water vapour.
Sensible Heat: The heat contained in the dry air content of an air/ vapour
mixture which affects the dry bulb temperature only.
Latent Heat: The heat contained in the vapour content of an air/ vapour
mixture.
Enthalpy (Total Heat): The sum of the sensible and latent heats of the air
and the water vapour it contains. It is measured in Kj/Kg of dry air in the
mixture.

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WHAT IS COMFORT
IF A HUMAN BODY IS TO REMAIN COMFORTABLE, HEAT
GENERATED WTHIN IT MUST BE REMOVED AT THE SAME RATE AS
IT IS PRODUCED. DURING PERIODS OF HEAVY PHYSICAL WORK,
BODY HEAT LOSS INCREASES AND GREATER USE OF COOLING IS
REQUIRED, AT TEMPERATURES APPROCHING BLOOD HEAT,
COMBINED WITH HIGH HUMIDITIES, THE BODY BECOMES
UNCOMFORTABLE.
DESIRABLE INTERNAL CONDITIONS FOR HUMAN OCCUPATION
ARE TYPICALLY 19’C IN WINTER AND 24’C IN SUMMER.
USUAL HUMIDITY COMFORT CONDITION IS SPECIFIED BETWEEN
40% TO 60%.

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THE PSYCHROMETRIC CHART
FOR CALCULATIONS RELATED TO THE PROPERTIES OF MOIST AIR
A PSYCHROMETRIC CHART SHOULD BE USED.
THE CHART IS ARRANGED SO THAT IF ANY TWO PROPERTIES OF
AN AIR VAPOUR MIXTURE ARE KNOWN THEN ALL OTHER
PROPERTIES CAN BE FOUND.
IF AIR IN A ROOM HAS A DRY BULB TEMPERATURE OF 20’C AND A
RELATIVE HUMIDITY OF 50%, THEN THE FOLLOWING
INFORMATION CAN BE CALCULATED FROM THE CHART:

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THE PSYCHROMETRIC CHART
WET BULB TEMPERATURE 14’C
MOISTURE CONTENT
DEW POINT
ENTHALPY
0.0074 Kg/Kg OF DRY AIR
9.4’C
38.8 Kj/Kg

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EQUIPMENT USED IN
AIR CONDITIONING

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AIR HEATING COIL:- This is a heat exchanger where air is passed
over its heated surfaces. The heat input can be via hot water, steam or
electric heating elements.

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AIR COOLING COIL:- This is similar in construction to the heating coil
but uses chilled water, or liquid refrigerant as the primary cooling medium.

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AIR FILTERS:- All air used in warm and air-conditioning systems must
be filtered to maintain a clean atmosphere in the conditioned space.

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HUMIDIFIERS:- These are equipment used to add moisture to the air.