Installation / Operation Instruction Manual

Page 70
Figure 42. Lead Lag Operation, 3 or more boilers
Low demand -
The first boiler in
sequence fires at
less than 65%
1 2 3 4
Demand increases -
Once the first boiler
reaches 65%,
the second boiler
switches on, and
both modulate
together between 20%
and 65% (this can be adjusted up to 20% and 85%).
Demand increases -
Once the first two
boilers reach 65%,
the third boiler
switches on, and all
boilers modulate together
between 20% and 65%. This continues as demand increases.
5 6 7 8
Nearing max. demand -
The last boiler becomes
active. Once all boilers
reach 65%, all are
allowed to go over
65%
The Lead/Lag controller will change the firing order of
the burners, based on the run time of each burner.
Number of boil-
ers installed
Base load value
1 NA
2 65%
3 50%
4 35%
5 35%
6 35%
7 35%
8 35%
Figure 43. Base Load Settings
Figure 41. “ Lead Lag” Operation in a System with Eight Boilers. Note: The Displays on
Boilers 2 through 8 will display information pertaining only to that specic boiler.
Touch
Screen
Lead Lag
Master
Addr
1
Addr
2
Addr
3
Boiler 4
Addr
4
Boiler 5
Addr
5
Boiler 6
Addr
6
Boiler 7
Addr
7
Boiler 8
Addr
8
Boiler 3Boiler 2
Boiler 1
Control Settings for Lead Lag Sys-
tem - Part 1
1. Power up all of the boilers in the
system.
2. In an installation with several boil-
ers, you must give each boiler a di󰀨erent
name, sot that the controller of the Lead
Lag Leader can communicate with the
other units. All of the units come from the
factory with a Modbus address of “1,” so
you will need to change some of these
addresses. On each unit, go to the screen
for “System ID and Access,” and enter a
unique name.
3. The unit operating as the Lead
Lag Leader must be ‘Leader Enabled’ rst
and then set up address “1,” and the other
boilers should each be ‘Follower Enabled’
and have unique Modbus address num-
bers typically 2 through X (total number of
boilers)
B RADFORD W HITE