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OptiSpeed Vaiable-Speed Drive Sales Guide - 160.07-SG1 (706) OptiSpeed
Variable-Speed Drive
Dont get caught in the chiller speed trap
OptiSpeed
Variable-Speed Drive
Dont get caught in the chiller speed trap Slow down and cut
energy use by 30%
Reduce energy costs
Energy is the number-one issue
facing centrifugal-chiller owners and
specifiers. Even the most efficient
constant-speed chiller consumes a
significant amount of energy.
Now you can reduce your energy
costs by adding a YORK
®
OptiSpeed
variable-speed drive to your new or
existing chiller. The result: an average
annual energy savings of 30%. These
savings are possible because no
constant-speed chiller, not even a
high-efficiency model, can match the
performance of an OptiSpeed drive
under real-world operating conditions.
The OptiSpeed variable-speed drive was
specifically developed for commercial air-
conditioning applications. No one matches
YORKs experience in the application
of variable-speed-drive technology to
chillers. Since pioneering the concept in
2
1978, YORK has installed more variable
speed drive chillers than all other chiller
manufacturers combined. So the success
of the OptiSpeed variable-speed drive is
not based just on theoretical test findings,
but real-world operating conditions.
YORK offers not only the most experience
of any manufacturer, but also the widest
application range. OptiSpeed drives are
available up to 3000 TR at 4160V.
Superior energy efficiency
To understand how a chiller equipped
with an OptiSpeed drive can offer up
to 30% lower energy costs, consider
the two factors that affect chiller energy
consumption: load and entering-
condenser-water temperature.
A reduction in either of these factors will
save energy. However, the method by which
the chiller is controlled has a major impact
on the magnitude of these savings.
A constant-speed chiller reacts to lower
load or lower entering-condenser-water
temperature by closing its pre-rotation vanes
(PRV), which throttle the refrigerant flow and
save some energy. However, as the vanes
continue to close, they create frictional
losses, which hurt the chillers efficiency
and limits its energy-saving capability.
On the other hand, it has long been known
that a far more efficient way to operate
a centrifugal chiller is with speed control.
When an OptiSpeed drive is used to
control a centrifugal chiller, the result
is 30% lower energy costs.
Pre-rotation vanes
cause frictional losses
as they close.
80
100
60
40
20
Load (%)
1.3
1.1
0.9
0.7
0.5
0.3
kW
/
ton
Constant Speed
30% Annual Savings
Variable Speed
This graph shows
typical energy savings
when an OptiSpeed
drive is installed on a
constant-speed chiller. Improved power factor
lowers energy costs
Power factor is an index of how effectively
your building uses electricity. A low power
factor translates into higher utility bills,
because utilities often charge a premium
if the usage profile doesnt meet their
minimum requirements. A high power factor
indicates efficient utilization of electrical
power. By adding an OptiSpeed drive with
a power factor in the area of 0.95 or better
throughout its entire operating range, most
utility requirements are met.
Smart control for
peak performance
With its Adaptive Capacity Control,
the OptiSpeed drive learns and remembers
optimum speeds for various load and
water-temperature combinationsa task
that no standard, variable-speed drive can
accomplish. The end result? Fine-tuned
chiller operation which provides maximum
energy savings.
3
The Adaptive
Capacity Control
learns and
remembers
Optimum Motor
Speed and PRV
Position for a given
set of conditions,
which fine-tunes
chiller performance.
Savings on multiple-
chiller plants, too
OptiSpeed drives will save in both single-
chiller installations and multiple-chiller
installations. In multiple-chiller installations,
cycling chillers off as the building load
falls will result in higher loads on the
remaining chillers. This would seem to
reduce the opportunity for OptiSpeed
drives to save energy.
Even though chiller loads remain high,
entering-condenser-water temperature has
most likely fallen. And reductions in entering
condenser-water-temperature offer a far
greater potential to enhance chiller efficiency
than load reductions do. Therefore,
OptiSpeed drives will deliver major energy
savings in multiple-chiller plants, too.
Multiple-chiller
plants benefit from
OptiSpeed drives.
Optimum
Motor Speed
Chilled Water Temp.
Temp. Setpoint
Evap./Cond. Pressure
PRV Position
Actual Motor Speed
Optimum
PRV Position
OptiSpeed
Variable-Speed Drive

Unlike constant-speed chillers, a variable-speed chiller
maintains a stable power factor. OptiSpeed drive delivers
more than energy savings
Better electrical protection
Electro-mechanical starters use a full-
speed start, with inrush currents reaching
as high as 250% of full-load amps. This
electrical inrush causes a tremendous heat
build-up, and flexing at critical points in the
motor windings. Over time, this repeated
flexing can damage the winding insulation
and eventually cause motor failure. For this
reason, a 30-minute cool-down period
is mandatory before a constant-speed
centrifugal chiller can be restarted.
By replacing the electro-mechanical starter
with an OptiSpeed drive, the chillers motor
starts more slowly. It never draws more
than 100% of its full-load amps. Motor heat
is reduced, as is the likelihood of electrical
shorts and burn-outs. As proof, chillers
controlled by an OptiSpeed drive can be
restarted in as little as 3 minutes, making
quick-turn, emergency restarts possible.
For further electrical protection, the
OptiSpeed drive is designed to reduce
electric-current harmonic distortion, which
can damage other equipment in the
building. As a standard, an OptiSpeed
drive reduces distortion to 26%, compared
to 80% distortion caused by competitive
drives. YORKs available harmonic filter
can reduce distortion to less than 4%,
which meets IEEE 519-92 and is a 95%
improvement over competitive drives.
Longer equipment life
While electrical safeguards protect
the electrical components of the chiller,
the mechanical components benefit
from lower operational speeds. Since
99% of operating hours are at less than
full-speed, moving parts experience less
component-wear, resulting in greater
reliability and longer life.
4
Compared to electro-mechanical starters, OptiSpeed drives reduce
current inrush and motor wear. The Optiview Control
Center provides
detailed information
on the operation of
the OptiSpeed drive.
5
Easier maintenance
and repair
When its time for maintenance, one
person can maintain the OptiSpeed drive
because it features a modular design.
If repairs are necessary, the OptiSpeed
drive can be serviced on-site, without
being shipped to a repair facility, reducing
chiller down-time. In the unlikely event
of an unexpected shut-down, the YORK
OptiView Control Center provides
troubleshooting messages and shutdown
data, enabling quick problem identification.
Additionally, maintenance is made
easier by single-source responsibility.
Factory-trained service personnel
service the chiller and all components
including the control systems.
Smaller footprint
Low-voltage OptiSpeed drives are mounted
directly on the chiller, which saves valuable
mechanical room floor space.
Medium-voltage drives have the smallest
footprint in the industry. The modular
cabinet design breaks down for ease of
installation, then bolts together in place.
Lower noise levels
On a centrifugal compressor, slower speed
means less noise. With an OptiSpeed
drive, 99% of operating hours are spent
at slower speeds, dropping noise levels
as much as 10 decibels.
Lower auxiliary
component costs
In addition to cutting energy costs,
OptiSpeed drives reduce auxiliary-
component costs. Their high power factor
eliminates the need for a power-factor-
correction capacitor. And in applications
that require a backup generator,
OptiSpeed drives let you specify a
smaller generator because the chiller
requires 60% lower start-up amps.
The medium voltage
OptiSpeed drives fit
back into the space
once occupied by
solid-state starters. P.O. Box 1592, York, Pennsylvania USA 17405-1592
Tele. 800-861-1001
Subject to change without notice. Printed in USA
© 2006 YORK International Corporation
www.york.com
ALL RIGHTS RESERVED
Form 160.07-SG1 (706)

Available as a retrofit
If you currently own a constant-speed
centrifugal chiller, retrofitting with a YORK
OptiSpeed variable-speed drive will
dramatically reduce your energy costs.
Its especially cost-effective when combined
with a refrigerant conversion or driveline
retrofit. Youll benefit from energy savings