Jetson FWCD Series, Installation Operation & Maintenance, Page: 62 / 96

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Total Supply Voltage
WARNING
Live Electrical Components!
Failure to follow all electrical safety
precautions when exposed to live electrical
components could result in death or serious
injury. When necessary to work with live
electrical components, have a qualified
licensed electrician or other individual who
has been properly trained in handling live
electrical components perform these tasks.
Measure each leg of the supply voltage at the line
voltage disconnect switches. For units with a
nameplate voltage of 208/230 volt, the readings
must fall within the range of 180253 volts. For
units with a nameplate voltage of 460 volts, the
readings must fall within the range of 414-506
volts. If voltage on any leg does not fall within
tolerance, notify the power company and request
correction of this situation before connecting to or
operating the unit. Inadequate voltage to the unit
will shorten the life of relay contacts and
compressor motors.
Voltage Imbalance Between Phases
Excessive voltage imbalance between phases in a
three- phase system will cause motors to overheat
and eventually fail. Maximum allowable
imbalance is 2 percent. Voltage imbalance is
defined as 100 times the maximum deviation of
the three voltages (three phases) subtracted from
the average (without regard to sign), divided by
the average voltage.
EXAMPLE:
If the three voltages measured at the line voltage
fused disconnect are 221 volts, 230 volts and 227
volts, the average would be:
221 + 230 + 227
3
= 226 𝑣𝑜𝑙𝑡𝑠
The percentage of imbalance is then:
100 (226 − 221)
226
= 2.2%
In the preceding example, 221 is used because it
is the farthest from the average. The 2.2 percent
imbalance that exists exceeds maximum
allowable imbalance by 0.2 percent. This much
imbalance between phases can equal as much as
20 percent current imbalance with a resulting
increase in winding temperature that will decrease
compressor motor life.
Equipment Grounding
CAUTION
Use Copper Conductors Only!
Failure to use copper conductors could result in
equipment damage as unit terminals are not
designed to accept other types of conductors.
Provide proper grounding at the connection point
provided in the unit control panel.
Unit Power Wiring
WARNING
Hazardous Voltage!
Failure to disconnect power before servicing
could result in death or serious injury.
Disconnect all electric power, including
remote disconnects before servicing. Follow
proper lockout/tagout procedures to ensure
the
power cannot be inadvertently
energized.
The installing contractor must connect appropriate
power wiring (with fused disconnects) to the unit-
mounted, non-fused disconnect in the power
section of the unit control panel. Electrical
schematics and component location drawings are
also mounted on the inside of the control panel
door.