NetNathan
Lifetime Supporting Member
Actually..... with most heating systems...
The High Limit control, to shut off heat, cannot be only in the PLC... NFPA 86 (Standard for Ovens and Furnaces) regulates this.
You MUST have a separate relay contact from the High Limit that breaks the PLC output for the heat contactor.
You can still send the signal to the PLC for alarms and any other control.
Also the High Limit instrument MUST be "FM Approved"....or no insurance coverage.
The High Limit control, to shut off heat, cannot be only in the PLC... NFPA 86 (Standard for Ovens and Furnaces) regulates this.
You MUST have a separate relay contact from the High Limit that breaks the PLC output for the heat contactor.
You can still send the signal to the PLC for alarms and any other control.
Also the High Limit instrument MUST be "FM Approved"....or no insurance coverage.
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