6-bms & hvac systems
DESCRIPTION
BMSTRANSCRIPT
Ibrahim kshanh www.ibrahim.kshanh.name
بسم الله بسم الله الرحمن الرحيمالرحمن الرحيم
Ibrahim kshanh www.ibrahim.kshanh.name
BMSHVAC
Evolution of
SYSTEMS With
Name of Presenter : Ibrahim Elsayed Kshanh
Title : Maintenance Specialist
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Contents1-Introduction To BMS
- BMS Objectives
2-HVAC Systems
- HVAC Control
- BMS Def.
- Building Automation & BMS (Supervisory Controls)
- DDC Control
-Control Theory (DDC Algorithm)
-Control Concept
-Modes of Control
-Control Valves & Valve Authority Concept
3-HVAC Automation
4-HVAC Instrumentation
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BuildingManagement
System
HVACSecurityAccess
Fire Others
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BMS Central Management
• Energy Management Techniques
• Maintenance Reports
• Automatic Alarm Reporting
•Long Term Trend data storage
Objective of BMS
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BMS
and HVAC Systems
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Self Contained
Unitary Units Central Systems
Ex: AC split units .VRV,…[Space Thermostat]
Or Electronic Control
Used when the first cost is more important than the operating cost
-Central Supply Subsystem
-End Use Zone Subsystems-Combination Ex: : Chiller or Boiler & AHU,FCU
Central AHU & VAV
HVAC
Heating, Ventilating and Air Conditioning System
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HVAC Control
HVAC:Heating, Ventilating and Air Conditioning System
Temperature (T): 20—25 C
Relative Humidity (RH) : 20% -- 60%
Pressure (P) : Slightly Positive
Ventilation : Air Quality
Comfort Condition
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HVAC Control
Chiller3
Chiller2
Chiller1
2-W
AY
LO
AD
S
Secondary Chilled Water Pumps
* * * *
Condenser
Evaporator
* * * *
Condenser
Evaporator
* * * *
Condenser
Evaporator
Primary Chilled Water Pumps
Condensed Water Pumps
Chilled & Condensed Water System
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AHU Control
An air handling unit (AHU)
air flow is from the right to left in this case. Some AHU components shown are:
1-Supply duct
2-Fan compartment3-Vibration isolator
4-cooling coil
5-Filter compartment6-Mixing box air duct
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AHU Control
MCC
Panel
M
M
M
M M
TSM
SM
CO2
AO
AO
AO
DI
AO
DIAI
DIAI
DO
DDC
Control Panel
Supply air
Exhaust airReturn air
E
H
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Chilled Water System Pressure Control
ControllerPID Loop
VFD
Main Return Header
Primary .Ch.W .Pumps
2-W
ay
Load
s
L
H L
H L
Secondary Ch.W.Pumps
DP
Main Supply Header
Chiller
Chiller
Chilled water system control
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DDC Control
• Electronic, Microprocessor Based
More accurate than pneumatic type
• With Free programmable SW Package
• Implementation of Energy Management techniques
• Open Protocols
Flexibility (sp, schedule ,override)
Energy cost saving
Promotes Integration
• Strong Alarm, Trends Capabilities
Facilitates Diagnostic and troubleshooting
• Web Based Provide Remote Access
Digital Microprocessor Based Controllers
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Building Automation & BMS (Supervisory Controls)
LCP/DDC LCP/DDC LCP/DDC LCP/DDC
Supervisory Control
Management level Network
Field level Network
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Control Theory
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Control Concept
The aim of The control is:
• To keep certain variable (Controlled Variable) within a desired value (set point) using certain calculations or programming instructions (Algorithm) that results in a corrective action (Control Signal) that affects the controlled variable directly or through another controlled variable (Automatic Control) in order to achieve a full system balance and overall desired performance
• To Maintain System Stability
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Controller)Algorithm(
Final Control Element
Process)Final Control Element(
External Disturbance
Sensing Element
Fe
ed b
ack
Clo
sed
loop
Co
ntro
l Corrective signal
Manipulated variable
Set point
Controlled variable
Implemented Control Loops
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1-Two-Position Control
On/Off Control
OnOff
Cycle
Time
Control Signal
Off Value 22
On Value 18
Diff
ere
ntia
l -
/+2
Set Pont:20
Zone Temp.
Time
Heating On/OFF Control:
Control Signal1 for T≤ Tmin
Zero for T≥ T max
Disadvantages: -Control Overshooting -Results in Cycling Process
Under shoot
Duty Cycle
Over shoot
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2-Time Proportioning Two-Position Control
Signal Converter
Analog Controller
Output 4-- 20 mA
Two Position Pulses with duty cycle
0%--100%
ControllerProcess Error
Signal
460540
ON Off
Control
Signal
On Off
Off
On
Cycle
Time
T ≤ 460
T =480
T≥540
T =500
T =520
460
Under shoot Pro
por
tiona
l Ban
d -
/+
40
Over shoot
Set Point:500
540
Proportional Band
1-Reducing the Average Power being supplied to a Heater
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2-Eleminates Cycling 3-Minimizing Offset
Application:
Heating Current Valve
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3-Floating /Three Position Control
ActuatorP
Controller
Common
DO2(OFF)DO1(ON)
Inlet Van
Damper
remain
openremainopen
remain close
Set point
Damper
position
Dead band
Time
Static Pressure
Damper Position is Linear and proportional to the On/Off Pulse Durations
Example :
Static Pressure Control
Pulse Duration
Time
DO1/2
Fully Open
Fully Closed
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4-Proportional Control (P)
From Process
Control Point
T
-
Set Point
TControl Signal = K p* Error K p :Controller Gain
4 – 20 mA
0—10 Vdc
Cooling Coil
Valve
To Process
Manipulated Variable
GPM
0% 100%50%
Set PointM : Bias or Manual Reset
+M
Cooling
Error
Control Output
Kp
M
Linear Relation
Time
ControllerKp
Error Signal
Control Signal Continuou
s
AO
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Proportional Control (P)
Throttling Range
Control Point T
Actuator Position
Set poin
tOffset
Control Point T
Time
Set Point
50%
100%
0%
Cooling
T1 T2
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5-Integral Control (PI)
•Automatic Reset
Eliminates offset
Cooling
Control Point (F)
50%
100%
0%
Actuator Position
Throttling Ranges
SP1
L1
SP2
L2
SP3
L3
Multiple Final Control Element Position for each
controlled variable value
The actuator final position depends on:
• Proportional Band (depends on actual load)
•Deviation signal Amplitude (E) and duration (dt)
Control Signal = K p* Error +
K I ∫e. dt
K I :Integral/Reset Gain
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Offset
Time
Control Variable
T
• Fast Response
• Zero st.st Error
• Excessive overshoot or integral windup
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gpm
AHU Control
P Temp. Control Loop
C
M
ControllerP
.
Controlled Variable
Compensation Sensor
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6-Derivative Control (PID)
Control Signal = K p* e+ K I ∫e. dt +Kd de/dtKd: Derivative Gain
Offset
Time
Control Variable
T
• Oscillation damping
• Noise Sensitive
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HVAC Instrumentation
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HVAC Control Valves
Control valves in HVAC are motorized valves commanded by BMS control signal , used to regulate the flow of the operating fluid that affects certain HVAC parameter
AHU Control
M
Controller
T
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Controllability
Output Energy
BTU 100%
50%
The best controllability is achieved by keeping Linear relationship between the Control output (which considered as the valve stroke ) and the output cooling
The controllability curve depends upon two c/cs,the valve flow c/cs & the cooling coil flow c/cs
Valve Opening100%50%0%
4mA Control Signal
20mA
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Typical Coil Characteristics:
O/P Energy%
BTU
Flow%
gpm
100%
At Const.
Water Temp.
Air Temp.
Coil Surface Area.
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Valves Flow Characteristics:
Flow%
Valve Stroke%
100%
100%Quick Opening
Linear Relationship
Equal Percentage
Theoretical /Inherent c/cs
Assuming Const.ΔP with flow
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Combined Valve & Coil Characteristics:Cooli
ng%
Flow %
100%
100%
Coil
Flow%
Valve Stroke%
100%
100%
Valve
Equal Percentage curve
Cooling%
Valve Stroke%
Coil Curve
Valve Curve
Best Controllability
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Flow%
Valve Stroke%
100%
100%
Equal Percentage valve Inherent C/Cs
Q = Qmax R) ]X/T-(1[
Q: Flow Rate (gpm)
X: Valve Position (in.)
T: Max Valve travel (in.)
R: Valve Rangiability
= Max Flow / Min Controllable Flow
Theoretical /Inherent c/cs
Assuming Const.ΔP with flow
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Equal Percentage Installed C/Cs
Total Pump Head
ΔPv
Curve deviation due to:
1-As valve closes ΔPv increases
M
ΔPc
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2-As valve closes, More Pump Head will be appeared across the valve
Pump Flow C/Cs
Pump Head
Flow% 100%
100%
Pump
System Curve
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To minimize the variation in the valve pressure drop (ΔPv)
Size the valve for initial pressure drop (ΔP v100% ) as close as possible to the close off pressure drop (ΔP v 0% ) which is equal to
the Total Pump Head
More Excessive Pump Energy Cost
&Unpractical solution
Larger Required Initial Pump Head
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Valve Authority Concept
N=
Open Valve Pressure Drop (ΔP v100% )
Closed Valve Pressure Drop (ΔP v 0% )
N=
ΔP v100%
ΔP v100% + ΔPc100%
N=0.5
Total P.H.
ΔPv
M
ΔPc
N= )ΔP v100%(
2 )ΔPv100% (
- Δ Pc 100%Open : ΔP v 100% = P.H.
Close Off : ΔP v 0% = P.H. - 0
P.H.= ΔP v100% + ΔPc100%
ΔP v 100% ≥ Δ Pc 100%
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Flow%
Valve Stroke%
100%
100%
N=33%
N=50%
N=10%
N=1%
N=5%
Authority and Valve flow curve deviation
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Valve Sizing and valve Authority
Kv=
ΔPv
Q
Kv Selection
Lower Kv Higher Kv
Assumed to be equals to ΔPc i.e. N=0.5
Kv: Valve ability to pass the flow
Q : Flow (M 3/hr)
ΔPv: Initial Pressure drop across the valve (bar)
ΔPv ≥ ΔPc
N: from 0.5 to 0.7N: from 0.5 to 0.7
ΔPv ≤ ΔPcN: from 0.3 to 0.5N: from 0.3 to 0.5
From TheFrom The ControlControl Point of ViewPoint of View From TheFrom The EnergyEnergy Point of ViewPoint of View
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Thank YouThank You
Ibrahim Elsayed Ibrahim Elsayed KshanhKshanh
الرحيم الرحمن الله الرحيم بسم الرحمن الله بسم
علما ) ) زدنى ربى علما وقل زدنى ربى (( وقل
العظيم الله العظيم صدق الله صدق
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