HydroTherm HeatNet KN -6 User Information page 88

TROUBLESHOOTING
c. If the Member boiler is in Local Mode then it also
would not be called and report unavailable to the
Master.
d. If the Local flow switch for the Local pump is
wired to the System flow switch input this would
also create an offline condition. The Member needs
to detect system flow or have a jumper across that
sensor input in
report available status. The Local flow prove
switch must be wired to the Water Flow interlock
sensor input.
Situation:
We are using a BACnet or LonWorks bridge. We
can talk to the bridge, but all of the data is zero (0)
or invalid.
This condition usually indicates that the bridge is not
communicating with the HeatNet control. When operating
properly, the bridge continuously reads data from the boiler
on the Modbus port into an internal buffer. When a BACnet
or LonWorks read request is received, the buffered values
are placed in a BACnet or LonWorks packet and sent. If the
bridge has never been able to successfully read data from
the control, all data points will have their default value
which is typically zero. In this situation, the control will also
not respond to write commands; for instance changing the
setpoint.
The control's MODBUS ADDRESS must be set to one
1.
(1). This is set in the ADVANCED SETUP-
>DISTRIBUTED CONTROL menu. On older
(legacy) firmware this setting was also called the
CONSOLE ADDRESS.
The control' BAUD (rate) must be set to 19200 and the
2.
DATA FORMAT must be set to 8E1 (8 data bits, even
parity, 1 stop bit). On older (legacy) versions of
firmware, the DATA FORMAT was called PARITY
which must be set to EVEN. These settings are set in
the ADVANCED SETUP->COMMUNICATIONS
menu.
3. Check the termination on the BMS/Modbus port. If the
control is the first or last device on the Modbus RTU
network, it should be terminated. For the short cable
runs (for instance when using a BACnet or LonWorks
bridge on a Revision 1.x board), the termination should
be in, but usually doesn't matter.
4. Check the wiring. The Modbus RTU (RS485)
connections on the HeatNet control are A(+), B(-), and
G (ground). Some systems use opposite polarity; A(-),
B(+). Always use the polarity to determine the proper
connections. A ground wire must always be used
order for the Member boiler to
and a shielded twisted wire is STRONGLY
suggested.
5. The HeatNet LonWorks and BACnet bridges plug
directly into Revision 2.x+ boards. Legacy boards
(Revision 1.x) required a ProtoCarrier to provide power
and the RS485 signal conversion to the bridge. The
RS845 signal conversion chips are easily damaged by
electrical noise, ground loops, and large differences in
ground potential between devices on the network. This
is a common problem faced by all RS485 devices, not
just the HeatNet control. To help eliminate grounding
problems, nylon standoffs are required to isolate the
bridge from the boiler chassis. The ProtoCarrier should
also be powered from the 24VDC output on the
HeatNet control to help eliminate electrical noise (VFD
and spark pickup, power spikes, etc.) on the power
supply lines. Please download complete HeatNet
bridge installation instructions from the product web
site.
a. When the ProtoCarrier is functional, the small
green surface mount TX and RX LEDs near the 6-
pin connector (power and communications) should
be flashing regularly.
b. If the TX LED flashes very briefly about once per
minute, the ProtoCarrier has most likely been
damaged, please contact Tech Services.
c. If either LED is always on, the ProtoCarrier has
most likely been damaged, please contact Tech
Services.
Situation:
We are using a Building Management System
(BMS) to control the boilers. We can write the
setpoints, but they keep changing back to their
―default‖ values after approximately 60 seconds.
1. When using a BMS, the setpoint values work in
conjunction with the SETPOINT TIMER. The
SETPOINT TIMER is a failsafe feature used to help
detect that a BMS is no longer working or
communicating with the control. The time must be
regularly loaded with a predetermined number of
seconds (1 – 65535). Every second this value will
decremented. If it reaches zero, the local (permanently
saved) values for the setpoints will be loaded. The
concept is that periodically (or every time a setpoint is
written), the BMS must write this value. If the value
reaches zero (0), the HeatNet control assumes that the
BMS in no longer functional and ―safe‖ operational
values for the setpoints will be restored. As an
example, if it is decided that the BMS will write the
control every 5 minutes, you may decide to write 600
HeatNet Control V3 2.x
Page 88