Installation / Operation Instruction Manual

Page 66
8.G.18 Lead Lag Leader Conguration
Conrm the Master control is ‘Enabled’.
If not enabled, press to select.
Select Master Control ‘Enable’
and Press OK
Note: The system sensor and outdoor sensor will
need to be wired to the Master boiler only.
The input from these sensors is used by the Master
control to control the modulation rate of all
of the operating boilers it is connected to. See the
manual for sensor and cascade wiring.
When a boiler is operating as part of a Lead Lag
system, it does not use the normal “CH set point” –
it uses the “Lead Lag CH set point” on the Master
control.
It is STRONGLY recommended to start each boiler
to complete combustion set up (See page 72
) and perform all safety checks before setting up
Lead Lag cascade.
Wiring Connections for Lead Lag -
The controller in each boiler includes two wiring
terminals for the Modbus system, labeled “MB1”
and “MB2.” MB1 has the wiring connections to the
User Interface display on each unit, and MB2 is
used to communicate with the other boilers in the
Lead Lag system.
For wiring connections to Lead Lag,
see Figure 34 on page 48
To reach the controller, open the cabinet of the
unit. The front panels on the indoor model pop o󰀨
when pulled forward. The outdoor model has two
latches that must be released on the sides before
pulling the panel forward and then up and o󰀨.
The wiring from the controller on the rst boiler
runs to the controller on the next boiler. Use 22
AWG or thicker shielded twisted-pair wire with drain.
Two twisted pairs or three conductors are needed.
Wire A on MB2 of Boiler 1 must be connected to A
on MB2 of Boiler 2, wire B on Boiler 1 goes to B on
Boiler 2, and wire C on Boiler 1 goes to C on Boiler
2. Repeat this wiring for any other boilers in the
system. Connect all of the drain wires and ground
the drain wire on one end of the assembly only.
The Conguration Menu
Select ‘Lead Lag Master Conguration’
B RADFORD W HITE