68
4. MODBUS = RATE (Rate Control Mode)
a. The VERSA IC
®
Control operates as a slave
to a Modbus master control (See table AA).
i. Operates as a single-boiler only (no cas-
cade)
ii. Pumps are turned on and off according to
the pump operation sent by the Modbus
master control
iii. No system sensor is required. The boiler
is operated at the target rate sent by the
Modbus master control
1.- A 1 to 100 integer value correspond to
a target firing rate from min+1 to
100%. Do not use negative integer
values.
To enable Modbus with the VERSA IC
®
Control, you
must first turn DIP switch #1 on the VERSA
®
Control
Board to the “ON” position to access the Advanced
menus. The lock icon on the upper right-hand corner
of the
VIEW
menu will disappear when configured cor-
rectly. From the
VIEW
menu press the
MENU
button
once to reach the
SETUP
menu. Using the
ITEM
but-
ton scroll to the
Modbus MODE
screen and select
either
MNTR
,
TEMP
or
RATE
for the functionality
desired. From there press the
ITEM
button to move to
the
ADDRESS
screen,
DATA TYPE
screen,
BAUD
RATE
screen and then
PARITY
screen to complete
setup for Modbus.
Modbus Communication
Values
The VERSA IC
®
Control has a setting called
Modbus
that determines how it operates when a external con-
troller using the Modbus protocol is connected, the
available settings are:
1. MODBUS = OFF
a. Modbus messages are ignored.
2. MODBUS = MNTR (Monitor Mode)
a. The VERSA IC
®
Control operates as usual,
however the Modbus connection allows for
remote viewing and adjustment of selected
VERSA IC
®
Control parameters (See table
AA).
3. MODBUS = TEMP (Temperature Control Mode)
a. The VERSA IC
®
Control operates as a slave
to a Modbus master control. The Modbus
handles all monitor functions and operates the
boilers, writing the Target Temp, Sys Pump
and DHW Pump data.
i. DHW and System Pumps are exclusively
turned on and off according to the pump
operation sent by the Modbus master con-
trol (See table AA). The VERSA
®
control
board does not control these pump out-
puts in this mode.
ii. Boiler pumps are operated as per usual
by the VERSA IC
®
Control.
iii. The boiler system is operated at the target
temperature sent by the Modbus master
control.
1. A non-zero 1 value below target min
will be interpreted as target min value.
2. A zero value will disable the unit.
3. Values within target min and max
range will call for heat whenever the
supply sensor reading is below target.
Summary of Contents for VERSA IC
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