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IM 817-7
Making Control Connections
Digital Ready™ – Face & Bypass
Control Components Model AVS
Digital Ready is a factory installed pre-wired package
of selected Direct Digital Control (DDC) components.
It facilitates the field hook up of a DDC Unit Ventilator
Controller (UVC) that is compatible with these factory
installed, pre-wired components, and capable of
providing the standard ASHRAE II cycle.
CAUTION
It is the responsibility of the Automatic Temperature Control supplier
to ensure the controls operate correctly and protect the unit.
Digital Ready consists of the following components
which are factory wired and powered:
1 .
Unit Main Power “On-Off” switch:
disconnects
main power to the unit for service. Non-fused power
interrupt switch
2 .
Fuse(s)
: fan motor, auto transformer and control
transformer have the hot line(s) protected by factory
installed cartridge type fuse(s).
3 .
Three (3) speed HIGH-MEDIUM-LOW-OFF motor
fan speed switch (SW2) .
4 .
75 VA 24-volt NEC Class 2 transformer:
for 24-volt
power supply.
5 .
Three 10-pole Europa type 16 awg terminal strips:
rated for 10 amps at 300 volts with nickel plated
connectors and zinc plated clamping screws (TB1,
TB2, TB3).
6 .
Space available in left end compartment,
approximately 8" x 21" (203mm x 533mm) for UVC
mounting (by others)
Wired to the Terminal Strips:
7
Interface with the fan motor start/stop relay, (R4) in
electric connection box.
8 .
Low Air Temperature Limit (T6 - Freezestat):
factory installed, cuts out below 38°F±2 °F and
automatically resets above 45°F±2 °F. Responds
when any 15% of the capillary length senses these
temperatures. Wired so that upon T6 cut out, the
outside air damper (A1) closes, the hot water valve
opens and the 24 volt power supply to the terminal
strip (T6 Sig) is interrupted.
9 .
Discharge Air Temperature Sensors (S2):
10 K
ohm NTC (Negative Temperature Coefficient) and 1 K
ohm PTC (Positive Temperature Coefficient). Located
on the second fan housing from the right to sense
discharge air temperatures.
10 .
Room Temperature Sensors (S1):
10K ohm (NTC)
and 1 K ohm (PTC). The unit mounted sensors are
located in the unit sampling chamber (front center
section), where room air is constantly drawn through
for prompt response to temperature changes in the
room.
11 .
Outdoor Air Temperature Sensors (S3):
10K ohm
(NTC) and 1 K ohm (PTC). The sensors are located
in the outdoor air section of the unit before the
outdoor air damper.
12 .
Outdoor Air/Return Air Damper Actuator (A1):
spring returned, direct coupled, proportional control (2
to 10 VDC or 4 to 20 mA)X.
13 .
Face and Bypass Damper Actuator (A3):
non-
spring returned, proportional control (2 to 10 VDC or
4 to 20 mA) .
14 .
End of Cycle DDC valves (not shown):
one or two
spring return actuators (by others), interface from the
terminal board providing 24-volt power. Open/shut
signal from UVC (by others).
15 .
24-volt power wiring harness:
from the right to left-
hand end compartment through the built-in metal wire
raceway terminating at three terminal blocks.
16 .
Low Refrigerant Temperature Sensor (T4):
capillary sensor, helps protect against abnormally low
evaporator coil temperatures. Direct Expansion (DX)
units only (not shown).
