HVAC, Heating Ventilation Air Conditioning BMS

Basic of Instrumentation
• Us our Body and its parts
• Our Body Reflexes

In BMS
INPUTS:- Sensors
Temperature(of room)
Humidity (of room)
Flow Rate (chilled Water)
Pressure(of Fire Hydrant)
Level (of a Tank)
Run status (Pumps, Fans)

Temperature Sensors
– Sensing technologies
• Thermistor
– Accurate over
limited range
– Point type only
– Used for space
temperature
• Nickel Wire
– General purpose sensor
– Point or averaging type
– Used for space or duct
– Application Issues
• Mount inside thermal well for
water temperature
• Mount return air sensor away
from fresh air stream
• Mount space temperature sensor :
– At 1500 mm height
– On inside wall
– Away from direct sun or
other heat sources
• Platinum
– High accuracy / linearity
– Point type only
– Precision applications
• Ensure off-coil sensors are far
enough away from coil
• Outdoor air temperature
sensors require sunscreen
• Calibrate using precision resistor,
validate using digital
thermometer
• Know mounting scope of
responsibility

Pressure Sensors
– Air Static Pressure
• Used to control VFD based on VAV
duct static
• Must be mounted in region of laminar
flow; five duct diameters from restrictions
• Active sensor
– Water Static Pressure
• Used to monitor pressure at top of sprinkler
riser
• Commercial grade sensors can leak
– Air Differential Pressure
• Used to calculate airflow from
velocity pressure
– PVELOCITY = PTOTAL - PSTATIC
– CFM = 4005 * AREA * (PVELOCITY
/ K FACTOR)½
• Used in VAV boxes and air flow
monitoring stations
– Water Differential Pressure
• Used to control bypass valve or VFD
• When controlling bypass, best to mount
at last AHU
• Do not try to save costs by using two
static pressure sensors
• Calculation error of same magnitude as signal
may ocur.

Other Sensors
Q Carbon monoxide
Q Control car park ventilation fans
Q Carbon Dioxide
Q Used as indirect indicator of
indoor air quality
Q Waterflow
Q Mount in region of laminar
flow; five diameters from
restrictions
Q Many technologies:
Q Annubar
Q Paddlewheel
Q Electromagnetic
Q Turbine
Q Humidity
Q Used to measure the Relative
Humidity in air.
Q Some humidity sensors comes
with in built temperature sensors
also.
Q Electrical Transducers
Q Current Transducers
Q Voltage Transducers
Q Lux Level Sensors
Q To measure the intensity of
light.

In BMSOUTPUTS:- Control
Valves
VFD Speed Command
Air DampersActuators
ON-OFF Command (Fans,
Pumps, Boilers)

INPUTS & OUTPUTS
INPUTS e.g
Analouge (varying-reading)
AI
Temperature, Humidity, Water Flow , Air
Flow , Tank Level, Energy KW, Voltage,
Current, Pressure, pH, Conductivity
Digital (Binary-ON or OFF)
DI or BI
Status (on/off, airflow , run, open/close)
Alarm
Trip
OUTPUTS e.g
Analouge (varying-positioning)
AO
Fan Speed regulating (0 to 100%)
Chilled water valvecontrol (0 to 100%)
Digital (Binary-ON or OFF)
DO or BO
Command (on/off, open/close)

I/O
Building management system relies on 4 types sensory information to make a control
decision Analog inputs : are used to read a variable measurement. Examples are temperature,
humidity and
pressure sensor which could be thermistor, 4-20 mA, 0-10 volt or platinum resistance
thermometer (resistance temperature detector), or wireless sensors.
Digital input : indicates if a device is turned on or not. Some examples of a digital input would be , an
air flow switch, or a volt-free relay contact.
Analog output : controls the speed or position of a device, such as a variable frequency drive, a I-P
(current to pneumatics) transducer, or a valve or damper actuator. An example is a chilled water
valve opening up 25% to maintain a setpoint.
Digital outputs : are used to open and close relays and switches. An example would be to turn on
the parking lot lights when a photocell indicates it is dark outside.
A typical Mid Size Building may have 800 -2000 sensory points also known and I/O
points. A complex Building like an Airport may have more than 5000 points

DDC Controllers
Q Types of DDC controllers
Q Fixed function
Q Configurable
Q Text programmable
Q Graphic programmable
Q Point Definition
Q Ranging (linear, calculated,
Q Control Loops
Q Proportional plus integral
control commonly used
polynomial)
Q Filtering (smoothing
and debounce)
Q Interlocks
Q Other software routines used in
local control logic
Q Minimum, maximum, average,
calculator, etc.
Q Psychometric calculations
Q Timing (delays, pulses, etc.)
Q Boolean and comparator
operators
Q Time clock and backup
schedules

Sl.
No
IO Description AI DI AO DO FIELD DEVICE
1 AHU On/Off 0 0 0 1 AHU panel to accept 2A NO contact
2 AHU Run Status 0 1 0 0 Differential Pressure Switch across blower
3 AHU Auto/Manual Status 0 1 0 0 Pot . free contact @ AHU Panel
4 AHU filter Status 0 1 0 0 Differential Pressure Switch across filter
5 Return air temperature 1 0 0 0 Duct type temperature sensor
6 2 Way chilled water modulating valve control 0 0 1 0 2 way Modulating Valve
7 Chilled water return header flow rate 1 0 0 0 Flow meter
TOTAL 2 3 1 1

Basics of HVAC
Pot with water
Evaporation through the pores of Mud Pot makes the water inside cool
Purpose of HVAC
The main purpose of HVAC is to provide the
people working inside the building with
“CONDITIONED AIR” so that they will have a
comfortable and safe work environment.

What is Conditioned Air?Conditioned Air” means that the air is clean and Odor-Free, and
the temperature, humidity and movement of air are within
certain comfort range.
Comfort Zone: (ASHRAErecommendation)
– –
– –
– –
Temp : 22.7oC to 26.1oC
Relative Humidity : 50%
Air Velocity : 30 feet per minute

What is AHU?
• AHU is Air Handling Unit
Contains:–Fan, Cooling coil , Air Filter

What is a Chiller
• A heat exchanger using air, refrigerant, water and evaporation to transfer
heat (BTUs) to produce air conditioning (measured in tons).
• A chiller is comprisedof an evaporator, compressor, condenser and
expansion valvesystem.

Building Management System-: Begin with the basics
• BMS – Building Management system
Building Automation system
•A BuildingManagement System (BMS) is
a blend of hardware & software based
control
control
system
and
installed
monitor
electrical
in buildings to
the building’s
& other utilitymechanical,
equipment

Building Services
Services Equipments
Mechanical system HVAC , Plumbing , Fire Fighting, STP
Electrical System Electrical DB’s/Lighting control & monitoring,
Generator set, UPS
Utility Lifts, FireAlarm System, Security System,Public
address system

What is a Building Automation System?
Q A BMS system collects the operating information required for intelligent building
management.
Q It analyses the operation of the building systems by viewing all important
temperatures, humidities and equipment status.
Q Further to collection of these data, the BMS presents these data on the screen with full
color
• Automates some control strategies such as turning equipment On/Off according to
a time schedule – ensures energy savings
• Allows an operator sitting at the BMS work station to view key information about
the building – improves building operations
• Allows an operator sitting at the BMS work station to control some of the equipment
in the building – improves building operations allowing remote control
/ over-ride where necessary
• Maintains an audit trail of what happened and when it happened – improves
building management by means reporting and traceability
• Maintains historical data for selected information (like temperature, humidity
..etc) – improves building management by means reporting and traceability
• Alerts the operator at the BMS work station when readings fall outside of normal
range (i.e. breaker trips, temperature too warm, etc.) – improves building
management by having a faster reaction time to problems
• By doing the above and more a BMS system saves manpower, ensures productive
occupants (especially in an office environment), prolongs equipment life, and the
most important of all saves energy. diagrams (graphics) for the ease of
understanding.

BMS Protocols
BMS system manufacturerdivided predominantly into two different
protocols,mentioned below-
• BACnet - A Data CommunicationProtocol for BuildingAutomation and
Control Networks developed by ASHRAE. It gives freedom to client to
connect all BACnet compliant devices and ease in commissioning&
configuring.
• Lonworks -Lon Works is actually a family of products originally developed by
the Echelon Corporation. At the core of this technology is a proprietary
communications protocol called Lon Talk. Here one needs to buy license for
each individual controllers & devices. Commissioning requires software key
(dongle) all the time for commissioning& configuration.
• Modbus is developed by Modicon in 1979. It is used to establish master-
slave/client-server communication between intelligent devices. It is a de facto
standard, truly open and the most widely used network protocol in the
industrial environment and devices.

BMS System
Architecture –• IP- 1 Tier
Where all controllers areconnected
to HMI on LAN.

RS 485 – 2Tier
Level1-: where all controllers are connected to
each other in daisy chain fashion & then after
they connect to router orgateway.
Level2-: When router or gateway is
connected to any HMI for monitoring &
controlling.

Building Automation System Software
User Interface
and Password
Energy
Operations
Maintenance
Operator Workstation (long term
storage)
Operator Workstation
Where this feature resides
ü
ü ü
Control Logic
Demand
Limiting and
Duty Cycling
Historical
Data
Graphics
Scheduling
Supervisory
Controller DDC
Controller
Supervisory
Controller
Operator Workstation
Supervisory
Controller
Supervisory Controller (processing)
Operator Workstation (long term
storage)
ü ü
ü ü ü
ü ü ü
ü
ü ü

BMS Typical BOQ-
It can be categorized in 3 broad categories-
POT(Portable Operator1. BMS controllers, Softwares,
Terminal),integration & PC.
2. Field Devices- It comprises different kind of sensors,
switches, actuators, Transmitters etc
3. Cables & conduits

1. BMS controllers, Software's, POT
(Portable Operator Terminal), for integration &
PC.
• Controllers selection can be done based on the IO (Input Output) requirements directly
just to match AI(Analog Input), AO(Analog Output), DI(Digital Input), DO(Digital Output) in
the layman’s language.
• Integration to collect the data from different devices.

2. Field Devices-
Comprises different kind of sensors,
switches, actuators, Transmitters
BMS
Areas
Categor
y Type
Sub-
Category
Application
AHU(Airside) Temperature(cu
m Humidity/RH)
Sensor Room To know the actual Temp inside without cooling
Duct
To know flowing
supply & Return Air
air Temp(& RH) inside duct for
Differential
Pressur
e
Across AHU Fan to check it is on or off physically,
Switch Air across filter to check the status
Valve & Actuators Across cooling coil
Chillers, cooling Temperature(cum To Know water temperature from the chillers &
to the
towers(Waterside) Humidity/RH) Sensor Immersion chillers
Outside To Know outside temp & RH
Differential
Pressur
e Switch
Water
Across Pumps to check it is on or off
filter to check the status
physically, across
Others
Level Transmitters Water To know the water level
Oil To know the oil level
CO2, CO sensor Room To know the air quality as in parking lot

3. Cable
It generally can be categorizedin two differentapplications-:
• Signal/ControlCable:From differentfield devicesto controllers &
from Controllers to field devices to controlthe equipments
• CommunicationCable:cable between differentcontrollers,routers
& gatewaysfor the purpose of intercommunication between
controllers.
• Integration cable:cable required for monitoring of third party
devices.

Cable Selection
BMS
Areas Category CableType Application
AHU Duct, Room Temp sensor 2c x 1 sqmm shielded PassiveTemp(2c) signals from sensor to controllers
Temp cum humidity sensor 4c x 1sqmm shielded
Passive Temperature(2c) & Active(2c-power) RH measurement from
sensor to controllers
DP Switch for Air 2c x 1 sqmm shielded Passive Temp(2c) signals from switch to controllers
AHU FAN VFD 2c x 1 sqmm shielded Run status
2c x 1 sqmm shielded On/off status
2c x 1 sqmm shielded Relay output for VFD On/OFFOperation
Valve & Actuator 5c x 1sqmm shielded Control & Power (3c power and command) & Monitor (2c)

Integration
BMS
Areas Category CableType Application
Integartion DG
2c x 1.5 sqmm twisted pair shielded Integration is only to collect data from different devices to monitor & generate
reports
UPS
reports
VAV's
reports
Electrical Panels
reports
Chillers
reports
Security & Fire Alarm
system
reports
Elevator
reports

BMS Design Aspects
Basic data required before you start system design:
1. Input / Output summary for all subsystems, which need to either monitor or control.
2. Selection of appropriate field devices.
3. All integration devices & respective point details which has to be monitored.
4. Signal & Communication cable route layout (at least tentative).
5. Panel (Enclosure for controllers) location, BMS PC location.
Steps to follow for designing-:
1. Select the suitable controllers required for the requirement.
2. Select the enclosure to mount those controllers, which includes power supply for controllers & other wirings for field device connection.
3. Now start with the AHU designing which includes signal & control cabling requirement for different field device selection as per the
requirement.
4. A typical AHU generally requires following field devices-Temperature cum Humidity sensor (or only Temp) in return & supply duct.
Differential Pressure Switch (For Air) across the AHU Fan, Filter, Actuators for AHU Line.
5. A typical AHU will have following wiring connection- Connection to all Field devices, Connection to electrical panels as per I/O,
connection to VFD’s.
6. A typical Chiller side will have following field devices-Immersion type temperature sensor (for supply & return pipes), Butterfly
Valve & Actuator in each chiller supply, differential Pressure sensor across main supply & return .
7. A typical chiller will have connection to all field devices, chiller panels, Pump VFD’s.

BMS Commissioning Aspects –
Air Side Commissioning- It comprises individual commissioning of AHU (Air handling Unit),
CSU (Ceiling Suspended Unit), Fans & associated field devices.
• We need to measure each field devices value during AHU commissioning as first task to
make sure all field devices are working & then all points can be put in alogic.
Water side commissioning – It comprises individual commissioning of Water cooled chillers,
Air cooled chillers, Cooling towers, Primary pumps, Secondary pumps, VFD’s & associated
field devices
• We need to measure each field device value & other connected points value individually
before putting them into logic.
Integration of Air side & water side in a logic-This is to integrate all independent system in
logic. Which can work automatically based on the user defined parameters without any
conflict of individual system functionality.

BMS Commissioning Aspects
Integration of monitoring points-
• This is to collect all data in BMS system for the purpose of monitoring only.
• PICS details i.e mapping details to be taken from respective equipment supplier.
• Protocol significance for integration purpose-whenever we say one device supports Modbus
over RS485, here RS 485 signifies physical channel (cable type) & communication port while
Modbus signifies data pattern. Therefore all devices in a loop must support same protocol &
configure to the same.
• Cable used for integration is 2 core x 1.5 sqmm shielded
• All monitored devices have to be looped in daisy chain connection to RS-485 port. Devices can
support different communication over different protocols. We need to make sure whenever
making a loop all devices should support same communication & protocol type. for instance
Modbus over RS485.
Client User interface (UI)
• Client can change parameters as temperature & humidity from UI as per the comfort level &
all basic information can be viewed on the UI.

HVAC, Heating Ventilation Air Conditioning BMS

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