Chapter 4 Troubleshooting & Repair
FastFlo™ 620S Instruction Manual
4-2
IM-62S
Problem
Possible Cause
Solution
Velocity measurement is er-
ratic or fluctuating
Very erratic or non-uniform flow
Follow installation requirements given in
Chapter 2
Flow meter installed with less than
required pipe diameters upstream
and downstream of the sensor
Follow installation requirements shown in
Chapter 2
Insertion sensor probe not mounted
securely
Sensor probe must be mounted securely
without vibration
Sensor component broken
Return to factory for replacement
Malfunction in system electronics
Return to factory for evaluation
Ground loop
Check wiring, see Chapter 2
Moisture present in the gas flow
Install a water trap or filter upstream of
the flow sensor
Velocity measurement
seems too high or low
Sensor assembly not aligned
correctly to flow
Correct alignment with the flow indicator
pointing downstream
Sensor probe not inserted to the
proper depth
Verify sensing point is located on the
centerline of the pipe
FastFlo™
electronics programming is in-
correct
Check all settings, see Chapter 3
Flow profile influences
Correct with K-factor adjustment or find
another mounting location
Flow has exceeded the maximum
range of the flow meter
Reduce flow below the maximum range
shown on the meter’s nameplate or con-
tact the factory for re-calibration advice
Extremely turbulent flow
Do not place the meter near a ventilator,
static mixer or valve
No response to flow from
sensor assembly
No power
Turn on power to the flow meter
Low flow cutoff too high
Correct low flow cutoff programming
us
ing Sierra’s Smart Interface software
Flow rate below meter’s minimum
flow rating
Contact factory for instructions
Microprocessor locked
Switch off power, wait 10 seconds,
restore power
Sensor failure
Return to factory for evaluation
Printed circuit assembly defective
Return to factory for evaluation
