Trane Starters Engineering Bulletin page 57

other electrical loads. Branch circuit wires supplying the unit must have an ampacity greater than
the MCA.
Table 11, p. 58
copper wire, run in conduit, in air, for several common wire types and configurations. Where
required by the NEC the values in the tables have been adjusted for more than three wires in a
conduit.
Table 11, p. 58
temperature around the conduit is between 78°F–86°F (26°C–30°C);
p. 60
104°F (40°C) or less. Installations with ambient temperatures outside these ranges require an
additional ampacity adjustment for proper wire selection.
The tables provide an easy way to estimate wire size. Enter the appropriate table, knowing the
nameplate MCA of the chiller; a table value greater than the MCA indicates a valid wire/conduit
selection (for the conditions described earlier in this section).
Example
The example chiller has a remote-mounted wye-delta starter and the nameplate indicates an RLA
of 300 and an MCA of 384 at 460 volts.
If 75°C conductors are used, the supply leads from the distribution system to the starter are sized
using
of the following combinations:
•
•
•
Because this is a wye-delta starter the leads from the starter to the motor are sized differently than
the supply leads to the starter. If 75°C conductors are used the leads from the starter to the motor
are sized using
combinations are allowed:
•
•
•
Conductor ampacity tables
The wire selection tables
conductor and conduit combinations that will support the amperage draw of CenTraVac chillers.
Wire sizes are given in units of AWG (American wire gauge) or kcmil (thousands of circular mils),
also referred to as MCM or KCM.
Find the appropriate table based on voltage, wire temperature rating, and where the wire will be
used. A table value greater than the nameplate MCA indicates a valid wire/conduit selection (for
the conditions described earlier in this section).Then check that the selected combination will fit
in the starter lugs by reviewing the starter submittal data. Final wire size selection must be
confirmed by the Engineer of Record for the installation.
CTV-PRB004-EN
through Table 16, p. 60
through Table 14, p. 59
are for 2,001 V–35 kV applications where the ambient temperature around the conduits is
Table 11, p. 58. Comparing the MCA to the table values indicates the conductors could be any
one conduit containing three 600 MCM conductors
one conduit containing six 250 MCM conductors
two conduits containing three 3/0 conductors each, and so on
Table 12, p. 58. Comparing the MCA to the table indicates the following
one conduit containing six 300 MCM conductors
two conduits containing three 4/0 conductors each
two conduits containing six 1/0 conductors each
(Table 11, p. 58
Electrical System–Power Wire Sizing
are based on the 2011 NEC conductor ampacities tables for
are for 0–2000 V applications where the ambient
through Table 16, p. 60) may be used for estimating
Table 15, p. 60 and Table 16,
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