Communications; Failsafe Modes; Failsafe Requirements - HydroTherm HeatNet KN -6 User Information

OPTIONAL FEATURES

Communications

The H-Net control has the ability to communicate using the
MODBUS protocol with a building management system.
Most registers and functions are available for MODBUS
access. Access is allowed using the RS485 MODBUS PORT
connecter on the communication board. Version 2.x Control
has these connections integrated on the main board.
An optional BACNet or LonWorks bridge module can be
used to connect the MODBUS network to a BACnet or
LonWorks network. See Method 5 control.

Failsafe Modes

FAILSAFE MODES have been added to help protect systems
from loss of heat conditions. When using one of these modes
ensure that you connect any DAMPER control, or system
pump control to safely allow operation with the assumption
that the MASTER boiler or BMS system is DOWN.

FAILSAFE REQUIREMENTS:

1. Since the Member boiler that will be assigned the
Failsafe duty will always turn the system pump ON, this
boiler should not be used for DHW heating. If the Master
controls the system pump, then the Failsafe Member
boiler would need to control the system pump in parallel
with the Master boiler. Wire the System Pump contacts in
parallel with the Master.
2. If the combustion air damper is used as a common system
damper, the Failsafe boiler should be wired to control the
damper in parallel with the Master boiler.
3. The Failsafe boiler must have the LOCAL SETPOINT
set to the same setpoint temperature as the Master
boiler's SYSTEM SETPOINT.
Be aware that the boiler may start without a call-for-heat in
the FAILSAFE MODES. FAILSAFE MODES can be
accessed through the:
SETUP:AUX FUNCTIONS:FAILSAFE MODES.
The following are types of Failsafe conditions.
1. Building Management System Failure
If a BMS system is controlling the setpoint and enabling
the boiler system, a timer is provided to allow operation
of the system in the event that communications are lost
with the BMS system. The HeatNet boiler system will
run locally if communications is lost and this timer
expires due to the lack of being updated.
The system setpoint timer and system setpoint work in
tandem to externally control (i.e. a BMS - building
management system) the operating setpoint. The setpoint
(countdown) timer should be loaded with a timeout value
(in seconds) prior to writing the system setpoint. When
the timer reaches zero, the control assumes that the BMS
is no longer operating and the local setpoint (saved on the
control) is reloaded. If the setpoint timer is not written, a
default timeout value of 60 seconds is assumed. The
timer is automatically reloaded with the default value
when a setpoint is written.
The BMS mode is always on and no menu item
is available.
2. HeatNet Communications Lost
SETUP:AUX FUNCTIONS:FAILSAFE MODES:H-NET
COMM LOST:
This mode allows a member boiler to run in LOCAL if
the communications link via the H-NET cable is lost.
This includes the MASTER boiler losing its Control
board, Communications board, or the power on the
MASTER is switched OFF. When this MODE is set to
ON, and if the member boiler loses it's link (heartbeat
packet over the H-NET cable) to the MASTER Boiler,
this MEMBER will fire to the LOCAL setpoint.
The heartbeat packet over the H-NET cable
needs to be lost for 10 minutes.
This MEMBER boiler will continue to run at the LOCAL
setpoint until H-NET communications from the
MASTER boiler is re-established.
Ensure that this Member boiler's Damper and System
pump control are configured correctly with the
assumption that the Master is not powered. Also ensure
that any other System settings related to outside air
temperature sensing and system interlocks are set to
provide safe operation.
Domestic Hot Water can also be provided using this
mode. See the DHW section of this manual.
3. Low Temperature Protection
LOW TEMP: OFF, SUPPLY, HEADER, DHW, or
RETURN
This mode may be used by the MASTER or MEMBER
boiler and can be used as a type of freeze protection. In
this mode you may select which Sensor you wish to
monitor, or you may opt to turn this mode OFF. If you
select a sensor, you may then associate it with a
HeatNet Control V3 2.x
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