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Location: assembly/manuals Series 92 A/C Modulating Svc Manual Gen II Rev. A 11/15/19
Page 19 of 26
Motor 2 No Motion (stall)
A fault is detected when no actuator motion is detected while the Motor 2 output
is turned on. The fault can be cleared in the same manner as a Motor 1 Stall
(see above).
Double No Motion (stall)
If the DHC-100 detects no actuator motion in either direction, both motor outputs
will be disabled. The command signal cannot clear this condition; only manual
operation or a mechanical override can clear the fault. Alternatively, the DHC-
100 can be powered off and then on to temporarily clear the fault; however, this
practice should be avoided without permanently correcting the cause of such a
fault.
Feedback Alarm
A fault condition is detected whenever the feedback signal is out of range (that is,
less than 5% of potentiometer value or more than 95% of the potentiometer
value), or when any of the potentiometer connections are broken. Normal
operation resumes when the potentiometer is reconnected or back in range.
Loss of Command
If the command signal is disconnected, the fault indication will remain on until the
signal is reconnected. See LOSS OF COMMAND for details.
Command Out of Range
If the command signal goes out of range, the fault indication will remain on until
the signal is back in range. See LOSS OF COMMAND for details.
Stall Detection Feature
The Stall Detection feature of the DHC-100 (see FAULT INDICATORS)
essentially performs a similar function as commonly used torque switches;
however, the differences should be considered before eliminating torque switches.
The DHC-100 feature does not measure torque, but rather motion; if the load is
sensitive to excessive torque, the torque switches may be desirable. Since
common torque switches are mechanical devices, they can provide a fail safe
feature in the event of electrical failures (such as shorted wires or damage to the
DHC-100).
The Stall Detection feature is useful for detecting when any of the motOr wires
become disconnected. However, limit switches employed in actuators essentially
disconnect one of the motor windings. The DHC-100 will detect this as a motor
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