Carrier 38AKS028-044 - Manual (Page 7)

FIELD CONNECTIONS
1. Main Power — Bring wires from the fused disconnect
switch through hole in bottom rail of unit to control box
11 12 (Fig. 6 and 7) and connect terminals , , and
13 line side of terminal block TB1 (see Fig. 8 and 9A
or 9B). To comply with NEC Article 440-14, the discon-
nect must be located within sight from and readily ac-
cessible from unit.
2. 24-v Control Power — Units have single point power con-
nections. Control circuit is directly connected internally
to unit. Maximum 24-v control circuit is 3 amps.
NOTE: Wire runs use the following insulated wire:
LENGTH
INSULATED WIRE SIZE*
AWG mm 2
0-50 18 0.82
50-75 16 1.30
Over 75 14 2.08
AWG — American Wire Gage
*35 C minimum.
3. Control Circuit Interlock — An airflow switch may be
installed in the indoor air handler to prevent unit from
running when indoor air is not flowing. This switch (no.
HR81JE001) is available from Service Parts Center, or
equivalent can be field supplied. This should be electri-
cally interlocked in the control circuit, between thermo-
2 Y1 stat TC1 (stage 1, cooling) and terminal on TB3.
See Fig. 8 for typical field wiring. This is in the 24-v cir-
cuit. Wires must be run in conduit with ground wire.
4. Transformer Connections — See unit wiring label dia-
gram, notes 1 and 2, located behind compressor compart-
ment end access door.
IMPORTANT: Ensure power to the crankcase heater
is always on (except when servicing the unit). If cir-
cuit breaker inside unit shuts down the compressor, crank-
case heater remains on.
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 percent voltage imbalance:
% Voltage Imbalance
max voltage deviation from average voltage
= 100 x
average voltage
Example: Supply voltage is 240-3-60.
AB = 243 v
BC = 236 v
AC = 238 v
243 + 236 + 238
Average Voltage =
3
= 239 volts
Determine maximum deviation from average voltage:
(AB) 243 − 239 = 4 v
(BC) 239 − 236 = 3 v
(AC) 239 − 238 = 1 v
Maximum deviation is 4 v. Determine percent voltage
imbalance:
4
% Voltage Imbalance = 100 x
239
= 1.7%
This amount of phase imbalance is satisfactory as it is be-
low the maximum allowable 2%.
IMPORTANT: Contact your local electric utility com-
pany immediately if the supply voltage phase imbal-
ance is more than 2%.
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