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APPENDIX C
Heater Burnout Option
The Heater Burnout option is used to detect heater burnout conditions
and to energize an alarm relay when such conditions exist. In most
cases, the option is used to detect the failure of one or more zones in a
multi-zoned heater where all individual resistive heater zones are wired
in parallel. Failed heater zones would create cold spots in a system
which could hamper the process and even ruin the product. If cold
spots in a system are a problem, the Heater Burnout Option is an effec-
tive way of alerting the operator of a heater burnout condition, a cause
of cold spots.
The controller is able to detect a heater problem by analyzing the cur-
rent used by the heater. The actual sensing is done by a current sens-
ing transformer, sold separately, which is placed around the hot lead
going to the heater and connected to the controller. The signal sent by
the current sensing transformer is timed with the output of the con-
troller. When the output is energized the signal sent from the current
sensing transformer is analyzed. When the output is de-energized the
signal sent from the current sensing transformer is not analyzed. This
eliminates the alarm condition turning on and off due to the output con-
dition of the controller. If the signal sent when the output is energized
indicates that the current level is below what the Heater Burnout alarm
is set for, the alarm is energized. The alarm is non-latching.
