HeatNet Smith Series, Руководство пользователя

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TROUBLESHOOTING HeatNet Control REV 1.38-1
Page 64
using a 0-10 VDC control signal it must be able to
supply the 20mA.
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.
1. The control’s MODBUS ADDRESS must be set to one
(1). This is set in the ADVANCED SETUP-
>DISTRIBUTED CONTROL
menu.
2. The control’s BAUD (rate) must be set to 19200 and the
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 and a
shielded twisted wire is STRONGLY suggested.
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 seconds (10
minutes) to the setpoint timer. If after 10 minutes (5
minutes longer than the normal write interval) the BMS
has not written the timer, the saved setpoint values will be
restored.
2. As a convenience, the SETPOINT TIMER is
automatically loaded with 60 seconds (if it has fallen
below 60) each time the setpoint is written. If you decide
to take advantage of this convenience, you would need to
write the setpoint periodically at less than 1 minute
intervals.
The SETPOINT TIMER failsafe feature can be disabled by
writing a zero (0) to the timer. The feature will automatically
revert back to the enabled state whenever the control is reset
or power cycled. The
SETPOINT TIMER failsafe feature
can permanently disabled in the
ADVANCED SETUP-
>COMMUNICATIONS
menu.