Trane Starters Engineering Bulletin page 78

Glossary
oil pump motor, and purge etc.) MCA is an output of the
TOPSS selection program.
Table 16, p. 60 show power wire sizing based on the
MCA.
Molded case switch
See "Non-fused disconnect" ,
Momentary power loss (MPL)
See "Distribution fault" , p.
Motor FLA
See "Amps, motor full-load amps (FLA)" ,
Motor LRA
See "Amps, motor locked-rotor amps (LRA)" ,
Motor size in kilowatts (kW)
The motor size is listed on the program output in kW. This
is the motor's full, rated capacity. There is an amperage
draw associated with power draw at full capacity called
full-load amps (FLA). FLA is the amperage the motor
would draw if it is loaded to its full rated capacity i.e.
motor size kW. The FLA is not available from the TOPSS
selection program, however can be obtained from
CenTraVac Field Sales Support.
Usually the selection RLA and kW are used as the
nameplate RLA and kW. Occasionally, an engineer may
decide to specify slightly higher RLA as the nameplate
data to provide "extra" capability for the chiller. The higher
kW and RLA cannot exceed the motor size (kW), the
starter size (RLA), or the disconnect/circuit breaker size
(RLA).
N
NEMA 1
Enclosures are intended for indoor use primarily to provide
a degree of protection against limited amounts of falling
dirt.
NEMA 12
Enclosures are intended for indoor use primarily to provide
a degree of protection against circulating dust, falling dirt,
and dripping non-corrosive liquids.
NEMA 3R
Enclosures are intended for outdoor use primarily to
provide a degree of protection against rain, sleet, and
damage from external ice formation.
NEMA 4
Enclosures are intended for indoor or outdoor use
primarily to provide a degree of protection against
78
Table 11, p. 58 through
p. 78.
75.
p. 73.
p. 73.
windblown dust and rain, splashing water, hose-directed
water, and damage from external ice formation.
NEMA 4X
Enclosures are intended for indoor or outdoor use
primarily to provide a degree of protection against
corrosion, windblown dust and rain, splashing water,
hose-directed water, and damage from external ice
formation.
Non-fused disconnect
A circuit breaker without a thermal or magnetic
overcurrent element. It is used solely as a manual
disconnect means. This is also called a "gutless" circuit
breaker or molded case switch.
O
Overload protection
A scheme or device that monitors motor current and
interrupts control power to the main contactor(s),
disconnecting the motor from the line, if motor current
exceeds preset limits of current and time. Motor current
may be monitored directly or through current
transformers.
Overload relay
A device that senses current flow to a motor. The relay
can be set to trip at a certain value. If the motor attempts
to draw current in excess of this value, the relay will trip,
de-energizing the contactor coil, disconnecting the motor
from the line.
P
Phase failure
An opening in one of the three main power leads caused
by a blown fuse or broken conductor. This results in only
one phase being delivered to the load. Thus, phase failure
is the same as single phasing. Phase failure protection is
standard on CenTraVac chillers with microprocessor-based
chiller control panels and was available as a starter option
on older CenTraVacs.
Phase imbalance
An imbalance in the current level or voltage level among
the three phases. Phase imbalance can cause motor
overheating.
Phase reversal
A change in the desired electrical phase relationship.
Phase reversal causes motors to rotate in the wrong
direction.
CTV-PRB004-EN