LAARS NeoTherm LC NTV1700 - Install and Operating Manual - Manual (Page 48)

LAARS Heating Systems Page 44
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.
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.
Fig. 48 – Lead/Lag Arrangement in a Single-Boiler Installation
Fig. 49 – Lead/Lag Arrangement in a Multiple-Boiler Installation
Primary
burner
Primary
controller
Gas
valve
Gas
valve
Secondary
controller
Secondary
burner
Operator
interface
Boiler 1
Operator
interface
Boiler 1
Slave 4
Boiler 2
Slave 3
Slave 2
Lead Lag
Master and
Slave 1 Slave 6
Boiler 3
Slave 5
Slave 8
Boiler 4
Slave 7
Addr
1
Addr
2
Addr
3
Addr
4
Addr
5
Addr
6
Addr
7
Addr
8