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Page 42
Section 9
SETUP AND CONFIGURATION
9.1
Review of Lead/Lag Control
System
9.1.1
About Lead/Lag Operation
The boilers in this series are always set up for Lead/
Lag operation. In a single-boiler installation, there
are two controllers and two burners, as shown in
Fig. 49. The controller for the upper burner is set up
as the Primary control. For control purposes, this is
the Lead/Lag Master and also operates as Lead/Lag
Slave 1. The control for the lower burner is set up
as the Secondary control and operates as Lead/Lag
Slave 2.
Fig. 48 – Lead/Lag Arrangement in a Single-Boiler Installation
Operator
interface
Fig. 49 – Lead/Lag Arrangement in a Multiple-Boiler Installation
Boiler 1
Operator
Primary
interface
controller
Gas
valve
Secondary
controller
Boiler 1
Boiler 2
Addr
Addr
Addr
Addr
1
2
3
Lead Lag
Slave 3
Master and
Slave 1
Slave 4
Slave 2
On a multiple-boiler installation, each individual boiler
is still set up as shown in Fig. 48. The boiler controls
are arranged in a "daisy chain" using a Modbus
connection, with the Secondary control of one boiler
connected to the Primary control of the next boiler.
Up to four boilers, with up to eight controllers, can be
connected in this way. See Fig. 49.
Primary
burner
Gas
valve
Secondary
burner
Boiler 3
Boiler 4
Addr
Addr
Addr
4
5
6
7
Slave 5
Slave 7
Slave 6
B
W
RADFORD
HITE
Addr
8
Slave 8
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