Modbus Installation | 50
Cannot see/change
set point over
Modbus.
Check control type. Demand type controls use internal algorithms to
generate a signal telling the humidifier to operate at a certain output
percentage. These controls do not report the detected humidity level
or set point to the humidifier. As a result the set point and space
humidity levels cannot be monitored through Modbus when using
demand controls.
Sensor ("transducer") type controls report a sensed humidity value to
the humidifier. The set point is configured at the humidifier and the
humidifier uses internal algorithms to determine the output
percentage. Since the humidifier knows both the set point and
humidity level, these values may be monitored over the Modbus
connection.
Cannot establish
communication.
Check communication parameters. Condair humidifiers are capable
of Modbus RTU communication. Modbus TCP based systems require
a gateway to translate the information.
Check Parity, baud rate, and stop bits. Modifying parity and stop bit
parameters may be necessary for some Modbus networks.
Cannot read data
from point
Check addresses, some Modbus network controllers automatically
prepend the "40" for input registers and "30" for input registers.
Carefully ensure that addresses are mapped correctly. A single
incorrect address may cause loss of communication or faults for an
entire chain of humidifiers.
Check data type, some Modbus network controllers default to integer
or binary values depending on variable type.
Only some registers
report data.
Check the baud rate being used on the Modbus network. NH-EL,
NHTC, GSTC, SETC, MHTC, and NHRS units only support 9600 bps.
MES-2 and RH2 units can support 4800 bps, 9600 bps, or 19200
bps for communications. Use of faster baud rates may cause data
loss.
Check the polling rate being used. High polling rates can interrupt
responses from the previous poll of data causing incomplete data
transfer. A recommended polling rate is once per minute.
Humidifier will not
respond to set
point/sensor
values/ demand
values written over
Modbus.
Check that humidifier is configured for "Digital" or "Modbus" control.
Refer to the "Control Signal Settings" section for your humidifier
model.
If the setting is "Analog" the humidifier will look for a control signal on
the low voltage terminal strip only.
Humidifier will not
respond to
hardwired controls.
Check that humidifier is configured for "Analog" control. Refer to the
"Control Signal Settings" section for your humidifier model. If the
setting is "Digital" or "Modbus" the humidifier will look for a control
value to be written over Modbus only.
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