8
grounding
Warning:
the unit cabinet must have an uninterrupted or
unbroken electrical ground to minimize personal
injury if an electrical fault should occur. do not
use gas piping as an electrical ground!
This unit must be electrically grounded in accordance
with local codes or, in the absence of local codes, with
the National Electrical Code (ANSI/NFPA 70) or the CSA
C22.1 Electrical Code. Use the grounding lug provided in
the control box for grounding the unit.
thermostat connections
• The unit is designed to operate from a 24 VAC Class
II control circuit. The control circuit wiring must comply
with the current provisions of the NEC (ANSI/NFPA
70) and with applicable local codes having jurisdiction.
Thermostat connections should be made in accordance
with the instructions supplied with the thermostat and
the indoor equipment.
• The low voltage wires must be properly connected.
See
through the sealing grommet near the power entrance.
Recommended wire gauge and wire lengths for typical
thermostat connections are listed in
.
• Single stage or two-stage heating thermostats can
be used with this equipment depending on optional
accessories installed with the unit. Select a thermostat
that operates in conjunction with the installed
accessories.
• The thermostat should be mounted about 5 feet above
the floor 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 fireplaces, sunlight, lighting fixtures or convective
heat from warm air registers or electrical appliances.
Refer to the thermostat manufacturer’s instruction sheet
for detailed mounting information.
coPPer Wire SiZe — aWg
(1% voltage droP)
SuPPlY Wire lengtH-Feet
SuPPlY circuit
aMPacitY
200
150
100
50
6
8
10
14
15
4
6
8
12
20
4
6
8
10
25
4
4
6
10
30
3
4
6
8
35
3
4
6
8
40
2
3
4
6
45
2
3
4
6
50
2
3
4
6
55
1
2
3
4
60
Wire Size based on N.E.C. for 60° type copper conductors.
table 2. copper Wire Size
lead from the transformer terminal marked 240V and
connect it to the terminal marked 208V.
• Internally mounted circuit breakers are available as field
installed options. These circuit breakers can be used
as an electrical disconnect.
• Connect the line-voltage leads to the terminals on the
contactor inside the control compartment.
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 efficiency 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. Measure the line 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).
eXaMPle:
AB = 451V
BC = 460V
AC = 453V
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:
eXaMPle
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.
6
454
100 x
= 1.32%
eXaMPle
max voltage deviation
from average voltage
= 100 x
average voltage
% 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%.
