Trane Climate Changer M Series - Page 78

78 CLCH-SVX03C-EN
Startup
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 terminals 1TB1–5
and 1TB1–6.
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 the formula below,
Table 17 and Table 18.
In Table 18 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.
Table 17. Altitude adjustment factors
Airflow = k (cfm @ 10V)
or
Airflow = k (L/s @ 10V)
For example, if the VCM on a size 30 M-Series air handler at sea level
(k=1) has a 10-volt signal, it would represent 18,376 cfm (8672 L/
s) through the Traq damper. If the voltage were 6 volts, airflow
through the Traq damper would be 9,188 cfm (3,930 L/s).
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
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volts 2–()
8
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Table 18. Back or Top Inlet Traq Dampers - Air-Mixing and Economizer Section - VCM voltage versus airflow at sea level
Unit
Size
Part
Number
Traq Damper
Size (inches) Quantity
Total Area
ft
2
Peak Velocity
(fpm)
CFM@10VDC
Peak Velocity L/s@10VDC
03
DMP01123 13
1 0.9213
2500
2303 1087
06
2 1.8426 4606 2174
08
10 3 2.7639 6910 3261
12
DMP01124 16 3 4.1867 2650 11095 523614
17
21
DMP01125 24 2 6.2800 2700 16956 8002
25
30 DMP01663 20 3 6.5417 2650 17335 8181
35
DMP01125 24 3 9.4200 2700 25434 12004
40
50
DMP01126 28
3 12.8217
2700
34619 16338
57
66 4 17.0956 46158 21784
80 5 21.3694 57698 27230
100
6 25.6433 69237 32676
120