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The 38AUD is a dual-circuit, three-stage cooling unit. Select a
three-stage cooling thermostat, with or without supplemental heat-
ing as needed.
Select a thermostat cable or equivalent single leads of different
colors with minimum of five leads for 38AUZ or six leads for
38AUD unit. Check the thermostat installation instructions for ad-
ditional features which might require additional conductors in the
cable.
For wire runs up to 50 ft (15 m), use no. 18 AWG (American
Wire Gauge) insulated wire (35°C minimum). For 50 to 75 ft
(15 to 23 m), use no. 16 AWG insulated wire (35°C minimum).
For over 75 ft (23 m), use no. 14 AWG insulated wire (35°C
minimum). All wire sizes larger than no. 18 AWG cannot be
directly connected to the thermostat and will require a junction
box and splice at the thermostat.
CONTROL CIRCUIT WIRING
Control voltage is 24 v. See Fig. 14 and the unit's label diagram
for field-supplied wiring details. Route control wires through
the opening in unit's end panel to the connection in the unit's
control box.
CONTROL TRANSFORMER WIRING
On multi voltage units, check the transformer primary wiring
connections. See Fig. 20 or refer to the unit's label diagram.
If the unit will be operating at 208-3-60 power, remove the black
wire (BLK) from the transformer primary connection labeled
"230" and move it to the connection labeled "208". See Fig. 20.
NOMINAL
POWER
UNIT
NUMBER
SUPPLY
SIZE
OF
38AUZ
STAGES
V-Ph-Hz
208/230-3-60
A16
2
460-3-60
575-3-60
208/230-3-60
A25
2
460-3-60
575-3-60
NOMINAL
POWER
UNIT
NUMBER
SUPPLY
SIZE
OF
38AUZ
STAGES
V-Ph-Hz
208/230-3-60
A16
2
460-3-60
575-3-60
208/230-3-60
A25
2
460-3-60
575-3-60
NOTE(S):
a. See Legend and Notes for Tables 13 and14 on page 19.
Table 13 — 38AUZ Unit Wire/Fuse or HACR Breaker Sizing Data
VOLTAGE
RANGE
No. 1
Min
Max
RLA
187
253
25.0
414
506
12.2
518
633
9.0
187
253
30.1
414
506
16.7
518
633
12.2
VOLTAGE
RANGE
No. 1
Min
Max
RLA
187
253
25.0
414
506
12.2
518
633
9.0
187
253
30.1
414
506
16.7
518
633
12.2
Fig. 20 — Control Transformer Wiring
EXTERNAL DEVICES
The 38AU control transformers provide 24-v NEC Class 2 power
sources to energize external control devices. These devices will in-
clude the indoor fan motor contactor (or control relay). These de-
vices may also include liquid line solenoid valve (two on 38AUD
model), economizer control relay, supplemental electric heater
contactors or control relays and other devices selected by system
designer.
Control transformer TRAN1 provides control power through ter-
minal R to C on the field connection terminal strip TB for supply
fan motor interlock. This source may also be used to energize
economizer control relay and electric heater contactors or relays.
Maximum available power is 20 va. Check concurrent loadings by
external control devices. If the maximum concurrent loading ex-
ceeds 20 va, purchase and install the accessory Transformer-Relay
package (available for 208/230 and 460-v units).
38AUD Only
Control transformer TRAN3 provides control power through
terminals A1 (9) and A2 (10) to C for liquid line solenoids.
Maximum available power is 75 va. These outputs are
switched ON/OFF by the Solenoid Valve Relays.
COMPRESSOR
No. 2
LRA
RLA
LRA
Qty
164
25.0
164
100
12.2
100
78
9.0
78
225
30.1
225
114
16.7
114
80
12.2
80
COMPRESSOR
No. 2
LRA
RLA
LRA
Qty
164
25.0
164
100
12.2
100
78
9.0
78
225
30.1
225
114
16.7
114
80
12.2
80
18
a
NO C.O. OR POWERED C.O.
OFM
Power Supply
Fuse or
FLA
MCA
HACR
(ea)
Breaker
3
1.5
60.8/60.8
80/80
3
0.8
29.9
40
3
0.7
22.4
30
4
1.5
73.7/73.7
100/100
4
0.8
40.8
50
4
0.7
30.3
40
WITH POWERED C.O.
OFM
Power Supply
Fuse or
FLA
MCA
HACR
(ea)
Breaker
3
1.5
65.6/65.6
90/90
3
0.8
32.1
40
3
0.7
24.1
30
4
1.5
78.5/78.5
100/100
4
0.8
43
50
4
0.7
32
40
Disconnect Size
FLA
LRA
63/63
337/337
31
206
23
162
76/76
462/462
42
236
31
168
Disconnect Size
FLA
LRA
68/68
342/342
33
208
25
164
82/82
467/467
45
238
33
170
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