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IM 830-6
Making Control Connections
Digital Ready™ – Face & Bypass
Control Components Model AHF
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 confirm that 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. Interface with a factory installed Low Air Temperature
Limit (T6 - Freezestat):
cuts out below 38°F±2 °F and
automatically resets above 45°F±2 ºF. 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 (bottom panel with perforations),
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):
direct
coupled, proportional control (2 to 10 VDC or 4 to 20 mA)
(spring return).
13. Face and Bypass Damper Actuator (A3):
direct coupled,
proportional control (2 to 10 VDC or 4 to 20 mA) (non-
spring returned).
14. End of Cycle DDC valves (not shown):
(by others) with
spring return actuators. Interface from the terminal board
with one or two providing 24-volt power. Open/shut signal
from UVC (by others).
15. 24-volt power wiring harness (not shown):
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) (not shown):
T4 capillary sensor helps protect against abnormally low
evaporator coil temperatures. Direct Expansion (DX) units
only.
Figure 91: Component Locations (Horizontal Ceiling Unit Shown)
Bottom View
Left End View
Right End View
