32
Installation (Continued)
Controls using DC Analog Input/Outputs
Before installing any connecting wiring between the unit
and components utilizing a DC analog input\output signal,
refer to Figure 3-2 for the electrical access locations pro-
vided on the unit.
These components may include:
Field installed Discharge Air Sensor (8RT3 VAV units);
Field installed Chilled Water Sensor (8RT2 EVP units);
a. Wiring for the components utilizing a DC analog
input\output signal must be shielded cable (Belden
8760 or equivalent). Ground the shield at one end
only.
b. Table 3-7 lists the conductor sizing guidelines that
must be followed when interconnecting a DC binary
output device to the unit.
Note: Resistance in excess of 2.5 ohms per
conductor can cause deviations in the accuracy of
the controls.
c. Ensure that the wiring between the binary controls
and the unit’s termination point does not exceed two
and a half (2.5) ohms/conductor for the length of the
run.
d. Do not run the electrical wires transporting DC
signals in or around conduit housing high voltage
wires.
Table 3-7
DC Conductors
Distance from Unit Recommended
to Control Wire Size
000 - 499 feet 16 gauge
500 - 1000 feet 14 gauge
Economizer Actuator Circuit
Each unit ordered with the Constant Volume or Variable Air
Volume control option has the capability of controlling a field
installed economizer. The diagram below illustrates a typi-
cal economizer actuator circuit.
When connecting the economizer actuator control circuit to
the terminal board inside the unit control panel, refer to the
actual unit wiring diagram for terminal designation, i.e. W,
B, R, & Y. A separate power supply for the actuator(s) must
be field provided.
Economizer Actuator Circuit Legend
Device Device
Designation Description Parts And Notes
MM Modutrol M.H. M955, ( Up to 3 motors may
Motor be controlled as shown.Additional
motors must be slaved.)
TR Transformer M.H. 13081B; cover mounted
EC Enthalpy Control M.H. H2051046
MP Minimum Position M.H. S96A1012
Potentiometer
EFI Evaporator Fan Field Provided
Interlock
7TB8 Low Voltage Located in Temperature
Terminal Strip Controller Planel
R 1/4 Watt - 5% 1 Motor/Circuit = None Req.
Carbon 2 Motors/Circuit = 1300 Ohms
3 Motors/Circuit = 910 Ohms
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