66
SCXF-SVX01T-EN
to utilize the lowest possible humidity level when
considering economizer operation. In addition, it receives
space pressure information which is used to maintain the
space pressure to within the setpoint control band. Refer to
Figure 36, p. 66 for humidity vs. voltage values.
Figure 36. Relative humidity vs. voltage
Figure 37. Velocity pressure transducer/solenoid
assembly
Tube from low side
of Transducer
Pressure
Transducer
Ventilation
Control Module
Solenoid
Tube from high side
of Transducer
Tube from low side
of Velocity Ring
Ventilation Control Module (VCM)
(Available only with Traq™ damper option)
The ventilation control module (VCM) is located in the
airside economizer section of the unit and linked to the
unit’s UCM network. Using a velocity pressure transducer/
solenoid (pressure sensing ring) in the fresh air section
allows the VCM to monitor and control fresh air entering the
unit to a minimum airflow setpoint. See Figure 36, p. 66 for
a detail view of the velocity pressure transducer/solenoid
assembly.
An optional temperature sensor can be connected to the
VCM to enable control of a field installed fresh air
preheater.
Also, a field-provided CO
2
sensor can be connected to the
VCM to control CO
2
reset. The reset function adjusts the
minimum cfm upward as the CO
2
concentrations increase.
The maximum effective (reset) setpoint value for fresh air
entering the unit is limited to the system’s operating cfm.
Table 35, p. 66 lists the minimum outside air cfm vs input
voltage.
Table 35. Minimum outside air setpoint w/VCM
module and Traq™ sensing
Unit
Input Volts
CFM
SXWF 20 0.5 - 4.5 vdc
6,325-8,500
SXWF 22 0.5 - 4.5 vdc
6,325-9,350
SXWF 25 0.5 - 4.5 vdc
6,500-10,625
SXWF 29 0.5 - 4.5 vdc
8,700-12,325
SXWF 32 0.5 - 4.5 vdc
8,700-13,600
SXWF 35 0.5 - 4.5 vdc
9,100-14,875
SXWF 38 0.5 - 4.5 vdc
9,880-16,150
SXWF 42 0.5 - 4.5 vdc
11,200-17,859
SXWF 46 0.5 - 4.5 vdc
11,960-19,550
SXWF 52 0.5 - 4.5 vdc
14,250-22,100
SXWF 58 0.5 - 4.5 vdc
15,080-24,650
SXWF 65 0.5 - 4.5 vdc
16,900-27,625
SXWF 72 0.5 - 4.5 vdc
18,700-29,800
SXWF 80 0.5 - 4.5 vdc
20,800-29,800
Generic Building Automation System
Module Option
Generic building automation system module (GBAS)
provides broad control capabilities for building automation
systems other than Trane’s Tracer® system. A field
provided potentiometer or a 0-5 Vdc signal can be applied
to any inputs of GBAS to provide following points:
GBAS Analog Inputs
Four analog inputs that can be configured to be any of the
following:
• Occupied zone cooling
• Unoccupied zone cooling
• Occupied zone heating
• Unoccupied zone heating
• SA cooling setpoint
• SA heating setpoint
• Space static pressure setpoint
• SA static pressure setpoint
GBAS Binary Outputs
Five binary outputs to provide diagnostics, signaling up to
five alarms. Each of the five relay outputs can be mapped
to any/all of the available diagnostics. Each output contains
a dry N.O. and N.C. contact with a VA rating of 2 amps at
24 Vac.
GBAS Binary Input
One binary input for the self-contained unit to use the
demand limit function. This function is operational on units
Controls
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