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Lead Lag Control
Intelligent Boiler Sequencing
Lead-Lag Control
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Lead Lag Control
Agenda
•
Objectives
•
Explanation and Set-up Procedure
•
Mk7 communication features
•
Other Information and Illustrations
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Lead Lag Control
Overview of System Operation: Features and
Benefits
•
The principal objective of Lead-Lag Control is to ensure that
the minimum number of boiler/burner units are in operation
at any one time. The benefits from using Lead-Lag Control
include:
– Increased savings in electrical costs
– Reduction in thermal stresses on the boiler
– Increased overall plant efficiency
•
There are 2 variations of Lead-Lag software
– One for Heating Boilers
– One for Steam Boilers
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Lead Lag Control
Lead-Lag Control
•
•
•
A maximum of 10 MM modules may be interconnected by
a 2 wire screened data cable
Methods to identify the “lead” boiler by
– Connecting a mains voltage onto terminal #88
– Instructing the modules via the D.T.I. Module by
software
Once a lead boiler has been selected it works in the
following way
– Lead boiler identifies it’s own firing rate
– Lead-Lag software calculates the amount of heat
being contributed to the system by this
boiler
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Lead Lag Control
Options that must be set for both forms of
Lead-Lag
1.
Option #16 must be set to #1 or #3.
2.
Option #33 (MM identification) must be set correctly. Each
MM unit must have its own individual number (from #1 to
#10). If this is not set then the MM units with the same ID will
turn off and on repeatedly.
3.
The fuel flow metering must be entered. This is how the MM
units turn on and off, based on the firing rate of the burners.
4.
To enter the fuel flow metering press ENTER when option
#57 is set to #1 and this is displayed on the MM screen.
5.
The next time the burner starts the fuel flow metering
program will continue. The fuel valve angular position will be
displayed and the heat input must be entered. This is done
from high fire (position #1) down to low fire (position number
#10).
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Lead Lag Control
Setting the Burner Rating
Options #34 and #77
•
Both of these options set the rating of the burner. Option
#34 sets the value (e.g. 5) and option #77 selects the units
(e.g. MBtu/Horse Power/Mega Watt).
•
Example:
– Option #34 = 20
– Option #77 = 9
– Rating of burner = 20 MBtu’s
–
–
–
Option #34 = 20
Option #77 = 2
Rating of burner = 20 MW
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Lead Lag Control
Sequence Scan Time and its Importance
Option #35
•
•
•
•
The sequence scan time has critical effect on the
responsiveness of the system, as it dictates how often the
Lead can make judgements to turn burners on and off.
It is important to change this option, especially on steam
applications when there is a dynamic load.
Sequence scan time too long- sudden demand can cause the
header pressure to drop, e.g. a sudden steam demand from
an Autoclave
Sequence scan time too short- the system may bring another
boiler on when the previous boiler to be turned on had not yet
begun to contribute to the requirements, e.g. the sequence
scan time is set shorter than the purge time of a burner.
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Lead Lag Control
Steam Boiler Sequential Control
Option #41
•
•
•
1st state is “on-line/lead” - is when the boiler is operating purely
under the control of the MM module’s internal P.I.D. load controller
2nd state is “standby warming” – the header valve is shut. The
boiler operates at a reduced set point that is an offset from the
required value. In standby warming condition the burner can only
run at low fire and only runs for a number of minutes each hour
3rd state is “off-line” – is with the burner shut down and the boiler
cold.
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Lead Lag Control
Lag Boiler Operation in Standby Mode
Phantom set point only
operates on the on
times, option 54
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Lead Lag Control
Phantom Setpoint
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3-State Sequencing
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Lead Lag Control
100 PSI
HIGH LIMIT
100
95
85
HIGH LIMIT
100
95
100 PSI
85
85
3
SETPOINT = 100 PSI
PHANTOM = 20 PSI
SETPOINT = 100 PSI
PHANTOM = 20 PSI
3rd STATE = OFF
LF
FIRING RATE %
0 PSI
2
SETPOINT = 100 PSI
PHANTOM = 20 PSI
0
100
95
20 PSI
1
LF
HIGH LIMIT
0
LF
0
FIRING RATE %
RS485 2 WIRE DATA LINK
FIRING RATE %
RS485 2 WIRE DATA LINK
LEAD BOILER SELECTOR
120V
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3-State Sequencing
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Lead Lag Control
100 PSI
HIGH LIMIT
100
95
85
HIGH LIMIT
100
95
100 PSI
85
85
3
SETPOINT = 100 PSI
PHANTOM = 20 PSI
SETPOINT = 100 PSI
PHANTOM = 20 PSI
LF
FIRING RATE %
20 PSI
2
SETPOINT = 100 PSI
PHANTOM = 20 PSI
0
100
95
100 PSI
1
LF
HIGH LIMIT
0
LF
0
FIRING RATE %
RS485 2 WIRE DATA LINK
FIRING RATE %
RS485 2 WIRE DATA LINK
LEAD BOILER SELECTOR
120V
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Lead Lag Control
Steam Boiler Sequential Control
•
Parameter #87- change up threshold: if the total capacity of the
lead boiler reaches 95% (or value set in this parameter) then the 1st
lag burner will start to fire. If the total capacity for both boilers is
95% then the 2nd lag boiler will start to fire.
•
Parameter #86- change down threshold: if the total capacity of 3
boilers goes below 85% (or the value set in this parameter) then
the 2nd lag boiler will turn off. The lead and 1st lag boiler are able to
cope with the load requirements. If the total capacity of the 2
remaining boilers goes below 85% then the 1st lag boiler will turn off
since the lead boiler can cope with the load.
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2-State Sequencing
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Lead Lag Control
100 PSI
HIGH LIMIT
100
95
85
HIGH LIMIT
100
95
100 PSI
85
85
3
SETPOINT = 100 PSI
PHANTOM = 20 PSI
SETPOINT = 100 PSI
PHANTOM = 20 PSI
LF
FIRING RATE %
0 PSI
2
SETPOINT = 100 PSI
PHANTOM = 20 PSI
0
100
95
20 PSI
1
LF
HIGH LIMIT
0
LF
0
FIRING RATE %
RS485 2 WIRE DATA LINK
FIRING RATE %
RS485 2 WIRE DATA LINK
LEAD BOILER SELECTOR
120V
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Lead Lag Control
Low Pressure Steam Applications
•
If the setpoint is set to 20 psi (2bar) or less then low pressure
steam control is implemented
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3-State Low Pressure Sequencing
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Lead Lag Control
15 PSI
HIGH LIMIT
100
95
100
95
85
15 PSI
LF
0
HIGH LIMIT
100
95
85
85
15 PSI
1
2
SETPOINT = 15 PSI
AQUA STAT FACILITY
SETPOINT = 15 PSI
AQUA STAT FACILITY
0
120V
15 PSI
3
LF
FIRING RATE %
HIGH LIMIT
SETPOINT = 15 PSI
AQUA STAT FACILITY
3rd STATE = OFF
LF
FIRING RATE %
0
120V
RS485 2 WIRE DATA LINK
FIRING RATE %
120V
RS485 2 WIRE DATA LINK
LEAD BOILER SELECTOR
120V
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3-State Low Pressure Sequencing
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Lead Lag Control
15 PSI
HIGH LIMIT
100
95
100
95
85
15 PSI
LF
0
HIGH LIMIT
100
95
85
85
15 PSI
1
2
SETPOINT = 15 PSI
AQUA STAT FACILITY
SETPOINT = 15 PSI
AQUA STAT FACILITY
0
120V
15 PSI
3
LF
FIRING RATE %
HIGH LIMIT
SETPOINT = 15 PSI
AQUA STAT FACILITY
3rd STATE = OFF
LF
FIRING RATE %
0
120V
RS485 2 WIRE DATA LINK
FIRING RATE %
120V
RS485 2 WIRE DATA LINK
LEAD BOILER SELECTOR
120V
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2-State Low Pressure Sequencing www.autoflame.com
Lead Lag Control
15 PSI
HIGH LIMIT
100
95
HIGH LIMIT
100
95
85
15 PSI
100
95
85
3
SETPOINT = 100 PSI
PHANTOM = 20 PSI
LF
FIRING RATE %
0
120V
15 PSI
2
SETPOINT = 100 PSI
PHANTOM = 20 PSI
0
85
15 PSI
1
LF
HIGH LIMIT
SETPOINT = 100 PSI
PHANTOM = 20 PSI
LF
FIRING RATE %
0
120V
RS485 2 WIRE DATA LINK
FIRING RATE %
120V
RS485 2 WIRE DATA LINK
LEAD BOILER SELECTOR
120V
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Lead Lag Control
Shuffle Sequencing
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Lead Lag Control
Potential Applications
•
3 twin burners
•
3 single furnace
boilers
•
1 twin burner &
2 single furnace
boilers
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Lead Lag Control
Hot Water Sequencing/Lead Lag Control
•
Hot Water Sequencing
•
The following options must be
set correctly for hot water
sequencing to function
correctly:
• Option #53 – 0
• Option #41 – 0
•
Ensures that boilers that are
switched “off line” do not
contribute return temperature to
the water flow header and thus
diluting the flow temperature to
the building
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Lead Lag Control
Parameter 57 increased comms
Set this to the highest MM ID you are using. The bus driver will
then only request data from the number of units as set in
Parameter 57.
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Lead Lag Control
Further Parameters
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Lead Lag Control
IBS Diagnostic
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Lead Lag Control
IBS Diagnostic (Continued)
IBS screen shot showing diagnostic Par 83,84
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Lead Lag Control
Bus Driver
When using the lead-lag intelligent boiler sequencing (IBS), the
bus driver is now determined by the lowest MM ID number, as
set in Option 33. Previously this was always the lead boiler.
This assists in speeding up the communications between
boilers when sequencing and also with the DTI when used for
shuffle sequencing.
IBS screen shot showing bus driver (diagnostic)
Par 83,84
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Lead Lag Control
IBS Screen Shots
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Lead Lag Control
IBS Screen Shots (continued)
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Lead Lag Control
Trouble Shooting
•
Make sure only 1 lead boiler is selected
– Either via the DTI or a live input on terminal #88
(lead boiler select switch)
•
Fuel Flow Metering is correctly set
– This must be calculated and entered for all boilers
•
It is very important that the correct cable is used for
communication between boilers (Beldon 9501)
– Use a daisy chain configuration (only connecting the
screen at one end of the wire)
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Lead Lag Control
Trouble Shooting (continued)
•
Make sure only that there is no input on #94 &95 all units
must be in auto (modulating)
•
Make sure that option 47 (cold start routine) is not
optioned
•
Make sure that the reduced set point is not set, all boilers
should use the required set point or phantom set point
(standby warming)
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Lead Lag Control
Trouble Shooting (continued)
•
Difficulties with maintaining load can often be overcome
by making minor alterations to the sequence scan time
(option 35). Significant alterations to sequence scan time,
will have a significant effect on the systems
responsiveness
•
If using shuffle sequencing ensure parameter #101 is set
correctly
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Lead Lag Control
Thank you for listening.
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