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 specific 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 3
Boiler 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 different
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’ first
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)
LAARS Heating Systems
Summary of Contents for Neotherm NTH
Page 4: ...LAARS Heating Systems...
Page 36: ...Page 36 Figure 22 Hydronic Piping Single Boiler Zoning with Circulators LAARS Heating Systems...
Page 52: ...Page 52 Figure 36 Ladder Diagram 7 H Ladder Diagram LAARS Heating Systems...
Page 100: ...Page 100 Parts Illustration 4 Internal Components Sizes 750 850 LAARS Heating Systems...
Page 102: ...Page 102 Parts Illustration 6 Gas Train Components Sizes 600 850 LAARS Heating Systems...
