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E. Provide Safety Relief
A fusible plug is located on the compressor crankcase
(Fig. 8). Do not cap this plug. If local code requires additional
safety devices, install as directed.
Head Pressure Control
Fan cycling for head pressure control is a standard offering
but is functional on the cooling cycle only. Number 2 fan
cycles as a function of liquid pressure. Fan cycling pressure
switch cycles the fan off at 160 ± 10 psig as pressure
decreases and cycles back on at 255 ± 10 psig. Switch is auto-
matically bypassed in heating cycle. Table 6 shows minimum
outdoor ambient air temperature for full cooling capacity.
Fig. 8 — Location of Fusible Plug
Table 6 — Minimum Outdoor Air
Operating Temperature
%
UNIT
COMPRESSOR
541A
CAPACITY
100
120
67
100
180
67
*Applies to Cooling mode of operation only.
IV. STEP 4 — COMPLETE ELECTRICAL CONNECTIONS
A. Power Supply
Electrical characteristics of available power supply must
agree with nameplate rating. Supply voltage must be within
tolerances shown in Table 7. Phase unbalance must not
exceed 2%. Operation of unit on improper supply voltage or
with excessive phase imbalance constitutes abuse and is not
covered by warranty.
Per local code requirements, provide an adequate fused dis-
connect switch within sight of unit and out of reach of chil-
dren. Provision for locking switch open (off) is advisable to
prevent power from being turned on while unit is being ser-
viced. The disconnect switch, fuses, and field wiring must
comply with local requirements. Refer to Table 7 for electri-
cal data. Route power wiring through entrance in right-hand
corner post of unit. The power terminal block is sized to han-
dle either copper or aluminum wires. Unit must be
grounded. Affix crankcase heater warning sticker to unit dis-
connect switch.
B. Power Wiring
All power wiring must comply with applicable local require-
ments. Install a field-supplied branch circuit disconnect
switch that can be locked off or open. Run power wires from
disconnect switch through unit power opening and connect
to terminal block inside the unit control box. See Fig. 9.
MINIMUM
OUTDOOR
OUTDOOR
TEMP — F*
COIL
TEMP — F
Standard
Unit
90
35
80
45
90
23
80
36
C. 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:
Voltage Imbalance:
max voltage deviation from average voltage
= 100 x
EXAMPLE: Supply voltage is 460-3-60.
AB = 452 v
BC = 464 v
AC = 455 v
Average Voltage =
= 457 v
Determine maximum deviation from average voltage:
(AB) 457 – 452 = 5 v
(BC) 464 – 457 = 7 v
(AC) 457 – 455 = 2 v
Maximum deviation is 7 v. Determine percentage of voltage
imbalance:
% Voltage Imbalance = 100 x
This amount of phase imbalance is satisfactory as it is below
the maximum allowable of 2%.
Contact your local electric utility company immediately if
the supply voltage phase imbalance is more than 2%.
IMPORTANT: Contact your local electric utility company
immediately if the supply voltage phase imbalance is more
than 2%.
WARNING: Unit cabinet must have an uninter-
rupted, unbroken electrical ground to minimize the
possibility of personal injury if an electrical fault
should occur. This ground may consist of electrical wire
connected to unit ground lug in control compartment,
or conduit approved for electrical ground when
installed in accordance with NEC (National Electrical
Code), ANSI/NFPA (American National Standards
Institute/National Fire Protection Association), and
local electrical codes. Failure to follow this warning
could result in the installer being liable for personal
injury of others.
IMPORTANT: Operation of unit on improper power supply
voltage or with excessive phase imbalance constitutes abuse
and is not covered by Bryant warranty.
D. General Wiring Notes
1. A crankcase heater is wired in the control circuit so it
is always operable as long as power supply disconnect
is on, even if any safety device is open or unit stop/
start switch is off.
2. The power-circuit field supply disconnect should never
be open except when unit is being serviced or is to be
down for a prolonged period. When operation is
resumed, crankcase heater should be energized for
24 hours before start-up. If system is to be shut down
for a prolonged period, it is recommended that the
suction and discharge valves be closed to prevent an
excessive accumulation of refrigerant in the compres-
sor oil.
3. Terminals for field power supply are suitable for cop-
per, copper-clad aluminum, or aluminum conductors.
—
8
—
average voltage
452 + 464 + 455
3
7
457
= 1.53%
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