General Information
12
RT-SVX24J-EN
space pressure to within the setpoint control band. Refer
to
Figure 1
for the Humidity vs. Voltage input values.
Multi Purpose Module MPM (Optional - used
with Return Fan Control, Energy Recovery, and
Evaporative Condensers)
The MPM supports three optional features. The first of
which is return plenum pressure control by receiving
analog voltage information for measuring return plenum
pressure, calibrating that reading, and providing an output
to control the return fan speed (if variable speed
configured) in response to control algorithm requests.
This module also provides inputs and outputs for control
of all Energy Recovery feature devices including the
energy wheel, exhaust and outdoor air bypass dampers,
and recovery preheat. The liquid line pressure sensor
inputs for both refrigeration circuits are received through
the MPM in support of head pressure control on water-
cooled condenser units.
Modulating Dehumidification Module MDM
(Optional - used with Dehumidification
Control)
The MDM supports specific control inputs and outputs for
Modulating Dehumidification control including
modulating Reheat and Cooling valve control as well as
the Reheat Pumpout Coil Relay output. The Modulating
Dehumidification control algorithm provides control
requests to the MDM to accomplish proper
Dehumidification control.
Ventilation Control Module (VCM)
The Ventilation Control Module (VCM) is located in the
filter section of the unit and is linked to the unit UCM
network. Using a “velocity pressure” sensing ring located
in the outside air section allows the VCM to monitor and
control the quantity of outside air entering the unit to a
minimum airflow setpoint.
An optional temperature sensor can be connected to the
VCM which enables it to control a field installed outside air
preheater. An optional 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 outside
air entering the unit is limited to the systems operating
CFM. The following table lists the velocity pressure vs.
Input Voltage (see also
Figure 6, p. 17
.).
The velocity pressure transducer/solenoid assembly is
illustrated below. Refer to the
“Units withTRAQ™ Sensor,”
p. 101
for VCM operation.
Figure 1.
Humidity vs. current
Table 3.
Minimum outside air setpoint w/VCM and
TRAQ™ sensing
Unit
Input Volts
CFM
90-162 Tons
0.5 - 4.5 VDC
0 - 46000
Figure 2.
Velocity pressure transducer/solenoid assembly
