Carrier 38AU User Manual
Page 18
18
External Devices – The 38AU control transformers provide 24-
v NEC Class 2 power sources to energize external control de-
vices. These devices will include the indoor fan motor contac-
tor (or control relay). These devices may also include liquid
line solenoid valve (two on 38AUD model), economizer con-
trol relay, supplemental electric heater contactors or control re-
lays and other devices selected by system designer.
Control transformer TRAN1 provides control power through
terminal R to C on the CTB’s field connection terminal strip for
supply fan motor interlock. This source may also be used to en-
ergize economizer control relay and electric heater contactors
or relays. Maximum available power is 20 va. Check concur-
rent loadings by external control devices. If the maximum con-
current loading exceeds 20 va, purchase and install the accesso-
ry Transformer-Relay package (available for 208/230 and
460-v units).
Control transformer TRAN3 provides control power through
terminals A1 (9) and A2 (10) to C for liquid line solenoids.
Maximum available power is 40 va. These outputs are
switched ON/OFF by the Solenoid Valve Relays.
Table 11 — Electrical Data — 38AUZ*07-08 60 Hz Units
Table 12 — Electrical Data — 38AUD*12-14 60 Hz Units
LEGEND AND NOTES FOR TABLES 11 & 12
UNIT
SIZE
38AU
NOMINAL
VOLTAGE
VOLTAGE
RANGE
‡
COMPRESSOR
OUTDOOR
FAN MOTORS (ea)
WITHOUT POWERD
CONVENIENCE
OUTLET
WITH POWERD
CONVENIENCE
OUTLET
V-Ph-Hz
MIN
MAX
RLA
LRA
WATTS
FLA
QTY
MCA
MOCP
MCA
MOCP
Z*07
400-3-50
380
420
9.7
64
270
0.7
2
13.5
20
15.9
25
Z*08
400-3-50
380
420
12.2
101
270
0.7
2
16.7
25
19.0
30
UNIT
SIZE
38AU
NOMINAL
VOLTAGE
VOLTAGE
RANGE
‡
COMPRESSOR
1
COMPRESSOR
2
OUTDOOR
FAN MOTORS (ea)
WITHOUT POWERD
CONVENIENCE
OUTLET
WITH POWERD
CONVENIENCE
OUTLET
V-Ph-Hz
MIN
MAX
RLA
LRA
RLA
LRA
WATTS
FLA
QTY
MCA
MOCP
MCA
MOCP
D*12
208/230-3-60
380
420
7.8
51.5
7.8
51.5
270
0.7
2
19.0
25
21.3
30
D*14
208/230-3-60
380
420
10.6
74
10.6
74
270
0.7
2
25.3
30
27.6
30
FLA
—
Full Load Amps
LRA
—
Locked Rotor Amps
MCA —
Minimum Circuit Amps
MOCP —
Maximum Overcurrent
Protection
NEC
—
National Electrical Code
RLA
—
Rated Load Amps
‡
Units are suitable for use on electrical systems where voltage supplied to
the unit terminals is not below or above the listed limits.
NOTES:
1. The MCA and MOCP values are calculated in accordance with the NEC,
Article 440.
2. Motor RLA and LRA values are established in accordance with
Underwriters’ Laboratories (UL), Standard 1995.
3. The 575-v units are UL, Canada-listed only.
4. Convenience outlet is available as a factory-installed option and is 115-v,
1 ph, 60 Hz.
5. Unbalanced 3-Phase Supply Voltage
Never operate a motor where a phase imbalance in supply voltage is
greater than 2%. Use the following formula to determine the percentage
of voltage imbalance.
Example: Supply voltage is 230-3-60
AB = 224 v
BC = 231 v
AC = 226 v
Average Voltage =
(224 + 231 + 226)
=
681
3
3
=
227
Determine maximum deviation from average voltage.
(AB) 227 – 224 = 3 v
(BC) 231 – 227 = 4 v
(AC) 227 – 226 = 1 v
Maximum deviation is 4 v.
Determine percent of voltage imbalance.
% Voltage Imbalance
= 100 x
4
227
= 1.76%
This amount of phase imbalance is satisfactory as it is below the
maximum allowable 2%.
IMPORTANT: If the supply voltage phase imbalance is more than
2%, contact your local electric utility company immediately.
% Voltage Imbalance
= 100 x
max voltage deviation from average voltage
average voltage