There are three categories of control cabinets in which this function can be used to start the burner automatically.
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Plants without UPS supply and without monitoring of the main supply and control voltage.
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Plants without UPS supply but with monitoring of the main supply and control voltage.
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Plants with UPS supply and monitoring of the main supply and control voltage
If a UPS is installed, the HMI, the FSC as well as all IO modules in the control cabinet remain live even if the main power supply has failed. The control voltage and the actuators and motors supplied with this voltage are switched off.
You can also switch off the control voltage again (independent of the main supply) by pressing the Emergency Stop button and switch it on again using the HMI (automatically only after a detected "Blackout") or manually by pressing the button "Control voltage on".
Automatic burner start after voltage return
Automatic starting of the burner after power is restored can be activated. An automatic reset is performed and the burner is started. If monitoring for the control voltage is available, then the burner is only started if the control voltage is switched on.
A distinction must be made between two operating concepts:
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Start/stop via switch
The automatic start with reset is performed if the switch is set to start.
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Start/stop via pushbutton
The automatic start with reset is performed if the system was preselected before a power outage.
"Blackout" detection and automatic activation of the control voltage
The system detects a blackout based on the signals "Main voltage supply active" and "Control voltage active". A simultaneous drop in both signals is interpreted as a blackout.
If only the signal "Control voltage active" (main supply is retained) drops, the system detects an "Emergency Stop".
As long as the main voltage supply is available, the HMI detects the status of the control voltage. This status is also retained after voltage OFF on the HMI.
This is necessary in order to decide after a blackout whether the control voltage can be automatically switched on again by the HMI. The control voltage can be switched on again if the system detected a blackout but not an Emergency Stop and the main voltage supply has been switched on again.
The behavior applies equally to systems with or without a UPS. On systems without a UPS, all system components are de-energized during the blackout.