Start-Up
58 CLCH-SVX010A-EN
VCM (Transducer) Calibration. The VCM has an auto-
zero function that recalibrates the transducer once every
minute. When troubleshooting, allow for the recalibration
time before making any measurements.
Input Power. The only input the VCM needs is the 24 Vac
power connected to the J2 plug (green and black wires).
Output Velocity Signal. The 2 to 10 Vdc linear output
signal from the VCM represents air velocity. This voltage
can be converted to represent airflow (cfm or L/s) using
this formula and Table 4.
In Table 5, the cfm at 10Vdc is a calculated value based on
area and peak velocity. In certain situations, it can be
advantageous to raise the velocity of air through the
remaining Traq dampers by closing off one or more
dampers in the unit. The cfm at 10Vdc can be recalculated
based on the proportion of remaining Traq dampers or by
multiplying the remaining area of dampers by peak
velocity. Calculations are based on VCM voltage versus
airflow at sea level.
Figure 66. Traq damper terminal connections
Airflow = k (cfm @ 10V)
or
Airflow = k (L/s @ 10V)
For example, if the VCM on a size 30 air handler at sea
level (k=1) has a 10-volt signal, it would represent
24,492 cfm (11,559 L/s) through the Traq damper. If
the voltage were 6 volts, airflow through the Traq
damper would be 12,246 cfm (5779 L/s).
Table 4. Altitude adjustment factors
Sea level = 1.0
Elevation (feet) k
1000 0.982
2000 0.964
3000 0.949
4000 0.930
5000 0.914
6000 0.897
7000 0.876
8000 0.860
9000 0.846
10,000 0.825
volts 2–()
8
------------------------------
volts 2–()
8
------------------------------
Table 5. Back or top inlet Traq dampers - air-mixing and economizer section - VCM voltage versus airflow at sea level
Part Number
Traq Damper
Size (inches)
Quantity Total Area (ft
2
)
Peak Velocity
(fpm)
CFM @ 10VDC
Peak Velocity
L/S @ 10VDC
DMP01123 13 1 0.9213 2500 2303 1087
DMP01124 16 1 1.3956 2650 3698 1745
DMP01663 20 1 2.1806 2650 5779 2727
DMP01125 24 1 3.1400 2700 8478 4001
DMP01126 28 1 4.2739 2700 11540 5446
To Next Page
Loading...
