Fox Thermal FT3 - Installation Problems

Installation Problems
The following is a summary listing of problems that may be encountered with the installation of the
FT3 thermal mass ow meter.
1. Improper wiring connections.
Refer to Fig. 3.1 to 3.16 and "Wiring Precautions" in Wiring section (p. 33 to p. 49) for further
guidance.
2. Inadequate power source.
For FT3 models specied for 24VDC operation, the input voltage must be 24VDC ±10%. A
20 Watt power supply or greater is recommended for powering the FT3 to ensure it operates
properly under all temperature ventilation, and power on conditions. If the voltage supplied
at the input terminals of the FT3 is not within the range of 21.6VDC to 26.4VDC, a variety of
problems can occur including a dim display, inaccurate ow readings or faulty 4-20mA, pulse and
communication interface.
3. Flow measurement seems inaccurate.
• Check to ensure that the ow meter is installed so that the Flow Direction Indicator is pointing
in the direction of ow. Refer to Fig. 2.6 (p. 25). If not, change orientation of meter.
• Check that the insertion depth of the sensor/probe is correct. The end of the probe should be
adjusted as per Fig. 2.5 (p. 24).
• Ensure that there are a minimum of fteen diameters of straight pipe upstream of the sensor
and ten diameters downstream. If complex ow disturbances are upstream of the sensor,
extension of the straight pipe may be required to ensure accurate ow measurement. Contact
Fox Thermal for assistance.
• Ensure that pipe inside diameter in the meter matches data on the Fox Thermal Calibration
Certicate. The pipe inside diameter is programmed into the ow meter through the front
panel (see Flow Parameters, p. 67).
4. Erratic ow reading (especially a ow reading spiking high).
This may be a symptom of moisture in the ow stream. Fox Thermal ow meters are designed
to work in relatively dry gas applications only. Contact Fox Thermal to discuss resolutions to this
problem.
5. Flow meter is not responding to ow.
• Check to ensure adequate power is supplied to the ow meter. If things appear to be correct,
perform this functional test before calling Fox Thermal. Carefully remove the probe and sensor
from the pipe. For those ow meters with a display - and if the display is reading zero - blow
on the sensor to see if a response occurs. If nothing happens, take a damp rag or sponge and
place it in contact with the sensor. A reading should occur. Contact Fox Thermal Customer
Service with this information.
6. Display and/or 4-20mA signal reading above zero ow when no ow is occurring in the pipe.
If the reading is less than 5% of full scale, it is likely this is a normal condition caused by
convection ow created by the heated sensor. It does not mean that the zero of the instrument is
improperly set. The Fox Thermal sensor is extremely sensitive to gas ow and can even read the
small ow caused by convection. If this is an unacceptable condition, please contact Fox Thermal
Customer Service for alternatives.
7. Mismatched serial numbers.
If you have more than one meter, you must ensure that the serial numbers of meter, remote, and/
or ow body match one another. These items have been manufactured and calibrated to operate
as a unit and cannot be mismatched.
Troubleshooting | 118
Model FT3
Troubleshooting