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AUX1 Relay & AUX2 Relay Outputs
The AUX1 & AUX2 Relays (solid state) are present to allow users to control external valves, switches, or other controls based
on thermocouple measurements or other current conditions. Both of the AUX1/AUX2 Relays are configurable to be controlled
by any of the three thermocouple's setpoints (TC1, TC2, or TC3), a custom temperature, to switch upon Flame Fail on either
ignitor, to reflect a TMain solenoid (TMain Mirror), to be on during a Purge cycle, or via Modbus control. AUX1/AUX2
Relays are turned off ("NC" is connected to "COM") when the CSC400 system is off. If a thermocouple is enabled via the
menu system, it needs to be attached to a Type-K thermocouple to operate properly. The LED Display will indicate an alarm
and the system will be turned off if there is an open fault detected with the thermocouple (if enabled).
Example: TC1 Ignitor 1 setpoint controls the dry contact AUX1 Relay switching. "NC" is connected (shorted) to "COM" if the
TC1 measurement is lower than the TC1 IGN1 setpoint temperature. "NO" is connected (shorted) to "COM" if the TC1
measurement is higher than the TC1 IGN1 setpoint temperature.
Number
AUX1/2 Relay Operational Description (using TC1 and
TC3 setpoints as examples)
Closed
"NC" is connected (shorted) to "COM" if TC1 IGN1
measurement is lower than the TC1 IGN1 setpoint
temperature
Common connection in both AUX1 Relay switched states
Open
"NO" is connected (shorted) to "COM" if TC1
IGN1measurement is higher than the TC1 IGN1 setpoint
temperature
"NC" is connected (shorted) to "COM" if TC3
measurement is lower than the TC3 setpoint temperature
Common connection in both AUX2 Relay switched states
Open
"NO" is connected (shorted) to "COM" if TC3
measurement is higher than the TC3 setpoint temperature
Note: Both of the AUX1/2 Relays are configurable to be controlled by any of the three thermocouples: TC1, TC2, or
TC3 and may also have a custom setpoint temperature set as its switching point. Either relay may also be
configured to switch upon Flame Fail on either Ignitor or upon Modbus command, or other options. Both AUX
relays will turn off (connecting NC to COM) upon a shutdown.
Modbus / RS485 Communication Connections
The three Modbus/RS485 terminals are used for connecting the CSC400 Controller to a Modbus communications channel. The
CSC400 Controller is a Modbus Slave Device that implements the Modbus RTU protocol on an RS-485, half-duplex, physical
connection. The default Modbus communication parameters are 9600 baud, 8 data bits, no parity bits, one stop bit (“8N1”),
Modbus Slave ID (Modbus address) 2.
The RS485 signal naming convention used in this document and by many RS485 transceiver vendors is reversed from what the
EIA/TIA-485 specification states:
Documentation
Naming Convention
Specification
Name
A (“RS485 A +” or "D0 A+")
Non-Inverting, Transceiver
Terminal 1, V1 voltage (V1 > V0
for binary 1 (OFF) state
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