TSI Instruments FHC50 User Manual

Part Two
68
Troubleshooting Chart
Symptom
Possible Cause
Corrective Action
Actuator hunting.
Display indicates
steady velocity.
Control system is
unstable.
Go into CONTROL menu, SPEED item. Turn speed down
until hunting is eliminated. If speed is too slow see
manual section: Optimizing Controller Performance and
adjust accordingly to eliminate problem.
Displayed
velocity wildly
fluctuating.
Exhaust system
unstable.
Turn DIM to emergency if using a Model FHC50
controller. If velocity stabilizes, exhaust system is not
unstable.
Laboratory
supply air is
affecting the
sensor.
Check location of supply air diffusers. They should be
located as far from the velocity sensor as is realistic, 10
feet preferred, 6 feet minimum. Supply diffuser terminal
throw velocity must be less than 50% of the average
controlled face velocity. Velocity in the fume hood chase
(back side of sensor) should be less than 25% of the
average controlled face velocity. The supply diffuser must
be relocated if these parameters cannot be met.
Display
averaging is very
short.
Lengthen the time constant by entering the
CONFIGURATION menu, DISPLAY AVG item, and
increase the average time.
Controller needs
calibration.
Calibrate controller.
Analog output
does not work
properly.
Controller is
connected to
incompatible
equipment.
Enter the DIAGNOSTICS menu, ANALOG OUT item. A
number is displayed. Connect a voltmeter to pins 5 and 6
(6 pin connector). Pressing the  key increases the
displayed number and increases the voltage (current)
output. Pressing the  key decreases the number and
decreases the voltage (current) output. If no change
occurs, disconnect the analog out device and repeat
above procedure. If voltage now changes, the controller is
good, and the external device is defective. If no change
occurs, DIM is defective.
Displayed
velocity does not
match measured
velocity.
Velocity sensor is
dirty.
See Maintenance and Repair Parts.
Controller is not
calibrated.
See Calibration.
Velocity sensor is
not referenced to
room air.
The velocity sensor must reference air from the same
space as the fume hood space. If fume hood cabinet
extends above to the ceiling, a Model 8691 Sensor
Venting Kit must be installed.
Display does not
read zero flow at
zero flow.
Controller is not
calibrated.
See Calibration.
Velocity sensor is
not referenced to
room air.
The velocity sensor must reference air from the same
space as the fume hood space. If fume hood cabinet
extends above to the ceiling, a Model 8691 Sensor
Venting Kit must be installed.

TSI Instruments FHC50 Specifications

General

Brand	TSI Instruments
Model	FHC50
Category	Controller
Language	English