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The HK300B is equipped with the following protective
devices to protect the user and the machine:
Emergency stop switch
The emergency stop switch is monitored by the controller inputs. The input is connected to
ground when the switch is pressed. In the event of an e-stop condition the system mode is set to
OFF and all output functions are shut down by the controller.
Pressure Switch
The pressure switch is designed to protect the burners and burner coils in the even of a pump
failure. The pressure switch is a normally open switch that closes when senses 12PSI from the
pump. If the switch does not sense pressure it wont allow power to go to the burners.
Low Water Cut Off Switch
The low water cut off switch is in place to protect the burners and burner coils as well as the
circulating pumps in the unlikely event of loss of glycol. If the glycol goes down below the switch
level, the switch contacts will close and shut off power to the pumps and burners to avoid dam-
age.
High Limit Switch (aquastat)
The high limit switch is in place to be a backup to the other safety devices. It is an analog switch
that is set to 230°F, there is one on each coil. In the event that the burner coil was to heat up
past the user set point the High limit switch cuts the power to the burner to avoid overheating of
the coil.
Protective Devices
