Unbalanced 3-Phase Supply Voltage; Thermostat Connections; Optional Electric Heater Kits - Nordyne S5BP Series User Manual

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
= 100 x
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%.
Example
:
AB = 451V
BC = 460V
AC = 453V
Example:
Highest Value
Example:
6
100 x
= 1.32%
454
max voltage deviation
from average voltage
average voltage

Thermostat Connections

• Thermostat connections should be made in accordance
with the instructions supplied with the thermostat and
the indoor equipment.
• Single stage or two-stage thermostats can be used
with this equipment depending on optional accessories
(i.e. economizer) installed with the unit. Select a
thermostat that operates in conjunction with the installed
accessories. A typical commercial installation with an air
conditioner thermostat and air handler (with & without
an economizer) is shown in Figure 7 (page 15).
• The outdoor 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.
• 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 2.
• 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 2. Thermostat Wire Gauge

Optional Electric Heater Kits

Optional fi eld-installed electric heater kits are available
in 10 kw through 36 kw heating capacities. Split System
Air conditioners are designed to allow optional auxiliary
electric heat to be fi eld installed as required by the building's
particular heating load. The options available for each
unit are shown in the heater kit installation instructions.
Install the heater kits as directed by the instructions
supplied with the heater kit. Follow all cautions and
warnings as directed.
Length (Unit to T-Stat)
5-Wire
(Heating/Cooling)
25
45
70
110
9