CONTROL METHODS
HeatNet Control V3
Page 27
Heating Method 4 AA Input
HIGH FIRE input Control: The AA input will fire the boiler
at HIGH fire (maximum output of the boiler). No other
inputs can override this input.
AA
— High fire input
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.
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 SETTINGS:
COMMUNICATIONS: SETPOINT TIMER: OFF. If the
setpoint timer feature is set to ON, the SETTINGS:
COMMUNICATIONS: SETPOINT TIMER 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.
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.
Method 4: Close this
AA
contact
to run the boiler at High Fire.
