26
wiring connections on units with factory disconnects should be
made at the line side of the disconnect switch.
The internal power and control wiring of these units is fac-
tory installed and each unit is thoroughly tested prior to ship-
ment. Standard 62X units have an SCCR (short circuit current
rating) of 5KA. Contact the local service representative if assis-
tance is required.
It is recommended that an independent 115-volt power
source be brought to the vicinity of the rooftop unit for portable
lights and tools used by the service mechanic, if a factory-
installed convenience outlet is not on the unit.
FIELD POWER SUPPLY — The units are factory wired for
the voltage shown on the nameplate. Main power wiring
should be sized for the minimum wire ampacity shown on the
nameplate. An external weather-tight disconnect switch prop-
erly sized for the unit total load is required for each unit. Dis-
connect must be installed in accordance with local and/or na-
tional electric codes. This disconnect can be supplied by the
factory or by others.
Power wiring may enter the rooftop unit through the unit
base and roof curbs on all models. Install conduit connectors at
the entrance locations. External connectors must be weather-
proof.
All units must be properly grounded. The ground lug is pro-
vided for this purpose.
DO NOT
use the ground lug for con-
necting a neutral conductor. The unit must be electrically
grounded in accordance with local codes, or in the absence of
local codes, with the NEC (National Electrical Code) ANSI/
NFPA (National Fire Protection Association) 70 1981.
Once it is established that supply voltage is within the utili-
zation range, check and calculate if an unbalanced condition
exists between phases.
Use the following formula to determine the percent of volt-
age imbalance.
% Voltage imbalance
Example: Supply voltage is 460-3-60.
AB = 452 v
BC = 464 v
AC = 455 v
= 457
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 percent of voltage imbalance.
% Voltage Imbalance = 100 x (7 / 457)
= 1.53%
This amount of phase imbalance is satisfactory as it is be-
low the maximum allowable 2%.
Unit failure as a result of operation on improper line voltage
or excessive phase imbalance constitutes abuse and may cause
damage to electrical components.
Consult the wiring diagram furnished with the unit. These
units are custom designed for each application. The unit wir-
ing diagram is located inside the control panel of each unit.
When installing units without a factory-installed disconnect,
provide disconnect per NEC Article 440 or local codes. For non-
fused disconnects, size the disconnect according to the sizing data
provided on unit nameplate. If a fused disconnect is used, deter-
mine the minimum size for the switch based on the disconnect
sizing data and then coordinate the disconnect housing size to ac-
commodate the maximum overcurrent protection (MOCP) de-
vice size as marked on the unit informative plate. All field wiring
must comply with NEC and local codes. Size wire based on
MCA (minimum circuit amps) on the unit informative plate.
For electrical information, reference submittals. See Fig. 14
for the installation wiring diagram.
SENSOR WIRING — The 62X unit uses a variety of sensors
for control purposes. The sensors provided will depend upon
the features of the unit as detailed below.
All units are equipped with an outdoor air sensor (OAT) and
a combination of supply air temperature (SAT) and duct rela-
tive humidity sensor.
The combination sensor should be installed in the supply
duct downstream of the heat section. The sensor must be far
enough downstream of the heat section so that the discharge air
is adequately mixed for proper sensing. If the unit is not
equipped with heat, the combination sensor is factory installed
= 100 x
max voltage deviation from average voltage
average voltage
Average Voltage =
452 + 464 + 455
3
=
1371
3
IMPORTANT: If the supply voltage phase imbalance is
more than 2%, contact your local electric utility company
immediately.
CAUTION
The correct power phasing is critical to the operation of the
scroll compressors. An incorrect phasing will result in an
alarm being generated and compressor operation lockout.
Should this occur, power phase correction must be made to
the incoming power. Damage to compressor could result.
WARNING
Unit cabinet must have an uninterrupted, unbroken electri-
cal 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 com-
partment, or conduit approved for electrical ground when
installed in accordance with NEC; ANSI/NFPA, latest edi-
tion, and local electrical codes.
Do not use gas piping as an
electrical ground.
Failure to follow this warning could
result in the installer being liable for personal injury of
others.
WARNING
Disconnect all power to the unit before performing mainte-
nance or service. Unit may automatically start if power is
not disconnected. Failure to follow this warning could
cause personal injury, death, and/or equipment damage.
