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C22.1 Electrical Code. Use the grounding lug provided
in the control box for grounding the unit.
Unbalanced 3-Phase Supply Voltage
Voltage unbalance occurs when the voltages of all phases
of a 3-phase power supply are no longer equal. This
unbalance reduces motor effi ciency and performance.
Some underlying causes of voltage unbalance may
include: Lack of symmetry in transmission lines, large
single-phase loads, and unbalanced or overloaded
transformers. A motor should never be operated when a
phase imbalance in supply is greater than 2%.
Perform the following steps to determine the percentage
of voltage imbalance:
1. M e a s u r e t h e l i n e
voltages of your 3 phase
power supply where it
enters the building and
at a location that will
only be dedicated to the
unit installation (at the
units circuit protection
or disconnect).
2. Determine the average voltage in the power supply.
In this example, the measured line voltages were
451, 460, and 453. The average would be 454 volts
(451 + 460 + 453 = 1,364 / 3 = 454).
3. Determine the maximum deviation:
From the values given in step 1, the BC voltage
(460V) is the greatest difference in value from
the average:
460 - 454 = 6
454 - 451 = 3
454 - 453 = 1
4. Determine percent of
voltage imbalance by
using the results from
steps 2 & 3 in the
following equation.
% Voltage Imbalance
The amount of phase imbalance (1.32%) is satisfactory
since the amount is lower than the maximum allowable
2%. Please contact your local electric utility company if
your voltage imbalance is more than 2%.
10
Example
:
AB = 451V
BC = 460V
AC = 453V
Example:
Highest Value
Example:
6
100 x
= 1.32%
454
max voltage deviation
from average voltage
= 100 x
average voltage
COPPER WIRE SIZE — AWG
(1% Voltage Drop)
Supply Wire Length-Feet
200
150
100
6
8
10
4
6
8
4
6
8
4
4
6
3
4
6
3
4
6
2
3
4
2
3
4
2
3
4
1
2
3
Wire Size based on N.E.C. for 60° type copper conductors.
Table 2. Copper Wire Size
Thermostat Connections
Several thermostat options are available depending on the
accessories installed with the unit. See Figure 10 (page
15) for 208/230V units or Figure 11 (page 16) for 460V
units. Select a thermostat that operates in conjunction with
the installed accessories. The low voltage wires must be
properly connected to the units low voltage terminal block.
Recommended wire gauge and wire lengths for typical
thermostat connections are listed in Table 3.
IMPORTANT NOTE: The thermostat should be
mounted about 5 feet above the fl oor on an inside
wall. DO NOT install the thermostat on an outside
wall or any other location where its operation may
be adversely affected by radiant heat from fi replaces,
sunlight, or lighting fi xtures, and convective heat from
warm air registers or electrical appliances. Refer to
the thermostat manufacturer's instruction sheet for
detailed mounting and installation information.
Recommended T-Stat Wire
Thermostat
Wire Gauge
2-Wire
(Heating)
24
55
22
90
20
140
18
225
Table 3. Thermostat Wire Gauge
Blower Speed
CAUTION:
To avoid personal injury or property damage,
make certain that the motor leads cannot
come into contact with any uninsulated metal
components of the unit.
Supply Circuit
Ampacity
50
14
15
12
20
10
25
10
30
8
35
8
40
6
45
6
50
6
55
4
60
Length (Unit to T-Stat)
5-Wire
(Heating/Cooling)
25
45
70
110
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