A B C A B C A B C A B C of of of of B B B B M SM SM SM S

byBAS Consultant & Engineer

Basic of Instrumentation

• Us our Body and its parts

• Our Body Reflexes

In BMSINPUTS:- Sensors

Temperature (of room)

Humidity (of room)

Flow Rate (chilled Water)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

• Ensure off-coil sensors are far – Used for space or duct

• 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

– Water Differential Pressure

– 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

� Waterflow

� Mount in region of laminar flow; five diameters from restrictions

� Many technologies:

� Annubar

� Paddlewheel

� Carbon monoxide

� Control car park ventilation fans

� Carbon Dioxide

� Used as indirect indicator of indoor air quality

� Paddlewheel

� Electromagnetic

� Turbine

� Humidity

� Used to measure the Relative Humidity in air.

� Some humidity sensors comes with in built temperature sensors also.

indoor air quality

� Electrical Transducers

� Current Transducers

� Voltage Transducers

� Lux Level Sensors

� To measure the intensity of light.

In BMSOUTPUTS:- Control

Valves

VFD Speed Command

Air Dampers Actuators

ON-OFF Command (Fans, Pumps, Boilers)

INPUTS & OUTPUTSINPUTS 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 TripTrip

OUTPUTS e.g

Analouge (varying-positioning)AO

Fan Speed regulating (0 to 100%)Chilled water valve control (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 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

� Types of DDC controllers

� Fixed function

� Configurable

� Text programmable

� Graphic programmable

� Point Definition

� Ranging (linear, calculated,

� Control Loops

� Proportional plus integral control commonly used

� Other software routines used in local control logic

� Minimum, maximum, average, calculator, etc.

� Psychometric calculations

� Timing (delays, pulses, etc.)� Ranging (linear, calculated, polynomial)

� Filtering (smoothing and debounce)

� Interlocks

� Timing (delays, pulses, etc.)

� Boolean and comparator operators

� Time clock and backup schedules

DDC physical

Control System

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 waterEvaporation through the pores of Mud Pot makes the water inside cool

Purpose of HVAC

The main purpose of HVAC is to providethe people working inside the building with“CONDITIONED AIR” so that they willhave a comfortable and safe workhave a comfortable and safe workenvironment.

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. 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

Inputs to the Controller:

Outputs from the Controller:

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 comprised of an evaporator, compressor, condenser and

expansion valve system.

Cycle

Chiller Plant

Chiller Plant with BMS sensor

Chiller Plant Operation

Control Logic

Building Management System-: Begin with the basics

BMS – Building Management systemBuilding Automation system

A Building Management System (BMS)is a blend of hardware & software basedis a blend of hardware & software basedcontrol system installed in buildings tocontrol and monitor the building’smechanical, electrical & other utilityequipment

Building Services

Services Equipments

Mechanical system HVAC , Plumbing , Fire Fighting, STP

Electrical System Electrical DB’s/Lighting control & monitoring, Generator set, UPS

Utility Lifts, Fire Alarm System, Security System, Public address system

What is a Building Automation System?

� A BMS system collects the operating information required for intelligent building management.

� It analyses the operation of the building systems by viewing all important temperatures, humidities and equipment status.

� 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 operationsthe 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 manufacturer divided predominantly into two different protocols, mentioned below-

• BACnet - A Data Communication Protocol for Building Automation and Control Networks developed by ASHRAE. It gives freedom to client to connect all BACnet compliant devices and ease in commissioning & configuring.configuring.

• Lonworks -Lon Works is actually a family of products originally developedby the Echelon Corporation. At the core of this technology is a proprietarycommunications protocol called Lon Talk. Here one needs to buy license foreach 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 defacto standard, truly open and the most widely used network protocol in theindustrial environment and devices.

BMS System Architecture –

• IP- 1 TierWhere all controllers are connectedto HMI on LAN.

RS 485 – 2TierLevel1-: where all controllers are connectedto each other in daisy chain fashion & then after they connect to router or gateway.

Level2-: When router or gateway is connected to any HMI for monitoring & controlling.to any HMI for monitoring & controlling.

Building Automation System Software

Alarms

User Interfaceand Password

�

Energy

Operations

Maintenance

Supervisory Controller (processing)Operator Workstation (long term storage)

Operator Workstation

Where this feature resides

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Control Logic

Demand Limitingand Duty Cycling

Historical Data

Graphics

Scheduling

�

Supervisory ControllerDDC Controller

Supervisory Controller

Operator Workstation

Supervisory Controller

Supervisory Controller (processing)Operator Workstation (long term storage)

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BMS Typical BOQ-It can be categorized in 3 broad categories-

1. BMS controllers, Softwares, POT(Portable OperatorTerminal),integration & PC.

2. Field Devices- It comprises different kind of sensors,switches, actuators, Transmitters etcswitches, 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 directlyjust to match AI(Analog Input), AO(Analog Output), DI(Digital Input), DO(DigitalOutput) 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

Category Type

Sub-Category

Application

AHU(Airside) Temperature(cum Humidity/RH) Sensor Room To know the actual Temp inside without cooling

DuctTo know flowing air Temp(& RH) inside duct forsupply & Return Air

Differential Pressure Across AHU Fan to check it is on or off physically,Differential PressureSwitch Air

Across AHU Fan to check it is on or off physically,across filter to check the status

Valve & Actuators Across cooling coilChillers, coolingtowers(Waterside)

Temperature(cumHumidity/RH) Sensor Immersion

To Know water temperature from the chillers & to thechillers

Outside To Know outside temp & RHDifferential PressureSwitch Water

Across Pumps to check it is on or off physically, acrossfilter to check the status

OthersLevel 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 categorized in two different applications-:• Signal/Control Cable : From different field devices to controllers &

from Controllers to field devices to control the equipments

• Communication Cable : cable between different controllers, routers & gateways for the purpose of intercommunication between & gateways for the purpose of intercommunication between controllers.

• Integration cable : cable required for monitoring of third party devices.

Cable SelectionBMS

Areas Category Cable Type Application

AHU Duct, Room Temp sensor 2c x 1 sqmm shielded Passive Temp(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/OFF Operation

Valve & Actuator 5c x 1sqmm shielded Control & Power (3c power and command) & Monitor (2c)

Integration

BMS

Areas Category Cable Type 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

2c x 1.5 sqmm twisted pair

shielded

Integration is only to collect data from different devices to monitor

& generate reports

VAV's

2c x 1.5 sqmm twisted pair

shielded

Integration is only to collect data from different devices to monitor

& generate reports

2c x 1.5 sqmm twisted pair Integration is only to collect data from different devices to monitor

Electrical Panels

2c x 1.5 sqmm twisted pair

shielded

Integration is only to collect data from different devices to monitor

& generate reports

Chillers

2c x 1.5 sqmm twisted pair

shielded

Integration is only to collect data from different devices to monitor

& generate reports

Security & Fire Alarm

system

2c x 1.5 sqmm twisted pair

shielded

Integration is only to collect data from different devices to monitor

& generate reports

Elevator

2c x 1.5 sqmm twisted pair

shielded

Integration is only to collect data from different devices to monitor

& generate 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 a logic.

Water side commissioning – It comprises individual commissioning of Water cooled chillers, Air cooled chillers, Cooling towers, Primary pumps, Secondary pumps, VFD’s & associated field devicesdevices

• 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 Modbussignifies 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• 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.

SNAPS OF INSTALLATION

PANEL

SCHEMATICS-AHU

SCHEMATICS-TFA

SCHEMATICS-SCRUBBER

Water Tank

EXHAUST FAN

CHILLER

CHW & CDW PUMPS

COOLING TOWER