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VOLTAGE UTILIZATION
RANGE
Electrical power to the unit must meet
stringent requirements for unit to operate
properly. Total voltage supply and voltage
imbalance between phases should be within
the following tolerances.
Measure each leg supply voltage at all line
voltage disconnect switches. Readings must
fall within the voltage utilization range shown
on the unit nameplate (±10%). If voltage on
any leg does not fall within the tolerance,
notify the power company to correct this
situation before operating the unit.
Inadequate voltage to the unit will cause
control components to malfunction and
shorten the life of electrical components and
compressor motors.
PRE-START PROCEDURES
VOLTAGE IMBALANCE
Excessive voltage imbalance between
phases in all 3-phase system will cause
motors to overheat and eventually fail.
Maximum allowable imbalance is 2 %.
Voltage imbalance is defined as follows:
100x Va-Vd
% Voltage Imbalance =
Va
Where
Va = (V1 + V2 +V3) / 3(Average Voltage)
V1, V2, V3 = Line Voltages
Vd = Maximum Line Voltage deviation from Va
Example:
If the three voltages measured at the line 221
Volts, 230 Volts, and 227 Volts, the average
(Va) would be:
Va = (221 + 230 + 227)/3 = 226 Volts
then Vd = 221 Volts
The percentage of imbalance is then:
100x 226-221
2.2%
226
17
The 2.2% imbalance that exists in the
example above exceeds maximum
allowable imbalance by 0.2 %. This much
imbalance between phases can equal as
much as 20 % current imbalance with a
resulting increase in winding temperature
that will decrease compressor motor life.
WATER FLOW RATE
Establish a balanced water flow through the
unit. Flow rates should fall between the
minimum and maximum values indicated in
TABLE 3. Evaporator water flow rates below
the minimum acceptable values will result in
a stratified flow; this reduces heat transfer
and causes either loss of expansion valve
control or repeated nuisance low pressure
cutouts. Conversely, excessively high flow
rate may cause erosion in the water system.
CGA-SVX01A-EN
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