6
JOHNSON CONTROLS
Application Data
- continued
in thermal conductivity between copper and aluminum
cannot guarantee the required tight connection over a
long period of time.
Power Factor Correction Capacitors –
Capacitors can
be applied to a chiller for the purpose of power factor cor-
rection. For remote-Mounted electro-Mechanical Starters,
the capacitors should be located on the load side of the
starter. For YORK SSS, the capacitors must be located on
the line side of the starter. The capacitors must be sized
and installed to meet the National electrical Code (NeC)
and be verified by J
OHNSON CONTROLS.
Ampacity on Load Side of Starter –
electrical power
wire size to the chiller is based on the minimum unit am-
pacity. For YORK SSS, this wiring is done at the factory.
For remote starters, the National Electrical Code defines
the calculation of ampacity, as summarized below. More
specific information on actual amperage ratings will be
supplied with the submittal drawings.
• Six-lead type of starting (Star-Delta)
Minimum circuit ampacity per conductor (1 of 6):
Ampacity = .721 x compressor motor amps.
• Three-lead type of starting
(Across-the-Line, Autotransformer and
primary Reactor)
Minimum circuit ampacity per conductor (1 of 3):
Ampacity = 1.25 x compressor motor amps.
Ampacity on Line Side of Starter –
The only additional load on the circuit for the chiller would
be the control transformer, unless it is supplied by a
separate source.
125% of compr. + FLA of all other
Min. Circuit Ampacity = motor amps loads on the circuit
Branch Circuit Overcurrent Protection –
The branch
circuit overcurrent protection device(s) should be a
time-delay type, with a minimum rating equal to the next
standard fuse/breaker rating above the calculated value.
It is calculated taking into account the compressor motor
amps and may also include control transformer. Refer to
submittal drawings for the specific calculations for each
application.
MOTOR ELECTRICAL DATA
The smallest motor available which equals or exceeds
the Input power (kw) from the chiller rating program is
selected from Tables 3 and 4. The full load amperes (FLA)
listed in the tables are maximum values and correspond
to the maximum motor kw listed. when the Input power
(kw) is less than maximum motor kw, the FLA should be
reduced using the following equation:
FLA
=
Motor kw
x Max. Motor FLA
Max. Motor kw
The benefit from the FLA correction is the possible use of
smaller power wiring and/or starter size.
The locked rotor amperes (LRA) are read directly from
Tables 3 and 4 for specific Motor Code and voltage. This
is because the LRA is dependent only on motor size and
voltage and is independent of input power (kw).
Inrush amperes (IRA) depend on LRA and the type of
starter applied. The inrush can be calculated using a
percentage of LRA shown in Table 5.
