HydroTherm HeaetNet V3 KN-10, User Information

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CONTROL METHODS HeatNet Control V3 2.x
Page 27
Heating Method 5
MODBUS communications
The fifth method uses an RS485 digital communications
cable with the MODBUS protocol to control the boiler
using the H-Net network. The Boiler or Boiler network will
run as in Method 1, but instead of the HEAT DEMAND
input, a software form of the HEAT DEMAND input is
used (40001: Boiler/System Enable/Disable). See:
MODBUS COMMUNICATIONS section.
Figure 20 MODBUS connections
Modbus Using
RJ45 Cat 5 cable
Modbus Using
shielded 3 wire.
Building
Management
The System Setpoint Timer also needs to be loaded
periodically to allow the H-Net system to fallback to
Method 1 in the event communications is lost from the
Building Management System (BMS).
This feature can be turned off in ADVANCED SETUP:
COMMUNICATIONS: SETPOINT TIMER: OFF. If the
setpoint timer feature is set to ON, the ADVANCED
SETUP: COMMUNICATIONS: SETPOINT TIME may be
set to a time that allows any write to a MODBUS register to
reset the setpoint timer as long as it occurs within that time.
This will reset the setpoint timer without writing the
setpoint timer register. So, periodically writing the setpoint
register will automatically reset the setpoint timer as long as
the write occurs within that time window.
Protocessor option
An optional BACnet or LonWorks bridge module can be
used to connect the MODBUS network to a BACnet or
LonWorks network.
Figure 21 Protocessor bridge module option
This method allows enabling and disabling the boiler or H-
Net system, changing setpoints, reading boiler(s) status, or
temperatures remotely using digital commands. See the
section:
MODBUS Communications.