Copeland
Digital Scroll is the next generation of
variable capacity compression technology –
it provides variable capacity output from
10% to 100% seamlessly. This technology can
be applied easily for various applications –
VRF (Variable
Refrigerant Flow) systems, Rooftops,
Chillers, Packaged & split Units and also
for special applications like computer room
cooling. Developed in 1993, the first
application of this technology was done for
refrigerated marine containers in 1999. In
2000 ,the air-conditioning version of this
technology was first launched in Asia.
Today, over 500,000
pieces of these compressors are working in
the field all over the world in various
premium applications and the reliability has
been over 99.996%.
Advantages
Wide Capacity
Range
Capacity
from
10%-100%
results in
an unmatched
output from
the Digital
Scroll.
This wide
capacity
output is
continuous
and seamless
and is an
improvement
over the
inverter
technology,
where
capacity
outputs can
only be
achieved in
steps. The
seamless
delivery of
capacity
also ensures
that there
is a very
tight
control on
room air
temperature.
A wide
capacity
output also
contributes
to high
seasonal
energy
efficiency
of the
system.
Frequent
start-stops
of the
compressor
consume more
energy.
Wider
capacity
output of
the Digital
Scroll
reduces the
number of
start-stops.
High
Seasonal Energy Efficiency
For modulated
systems, single
point efficiency
is not the right
gauge when
measuring the
efficiency of
the system. The
seasonal energy
efficiency ratio
(SEER) has to be
calculated to
get a good idea
of the savings
from operating
the system
year-round.
The Digital
Scroll
performance has
been evaluated
as per JIS & ARI
standard and
showed excellent
SEER. The SEER
advantage
becomes even
greater for a
tandem
configuration –
a Digital Scroll
compressor in
tandem with a
fixed speed
compressor. At
full load
capacity, when
both compressors
are operating,
the system has a
high EER and at
50% capacity,
when only one
compressor is
operating at
full load, the
system operates
at high EER
also.
Oil return is a major issue in variable capacity multiple evaporator systems. Current technologies use an oil separator and/or complicated oil return cycle to ensure oil return after some period of operation. The Digital Scroll is a unique compressor – it does not require an oil separator or an oil return cycle.
There are 2 factors that make the oil return easy. First, the oil leaves the compressor only during the loaded cycle. So at low capacities, very little oil leaves the compressor. Second, as explained before, the compressor operates at full capacity during the loaded cycle. The gas velocity in the loaded cycle is sufficient to return oil to the compressor. Our testing has shown that oil is able to return to the compressor even in the worst operating conditions – low modulation, 100 meter pipe length and 30 meter elevation (with standard oil traps), both straight and reverse elevation.
Dehumidification is necessary to ensure comfortable living and this becomes more important during low modulation operation. In the inverter system, at low modulation, the compressor operates at a lower frequency. This reduces the mass flow of refrigerant and results in a higher suction pressure. This results in a higher Sensible Heat Factor (SHF).
The Digital Scroll compressor provides very good dehumidification because it operates at a lower suction pressure than the inverter. As mentioned before, given any modulation output, the compressor operates at full capacity during the loaded part of the cycle. This full capacity operation results in a lower average suction pressure that leads to a lower SHF.
Electromagnetic Interference is a major issue in inverter-driven systems. In many countries, particularly Europe, there are strict regulations on the amount of electromagnetic interference that any device can emit.
The Digital Scroll system generates negligible electromagnetic interference because the loading and unloading of the Scrolls are mechanical operations.. This unique feature not only eliminates the need for expensive electromagnetic suppression electronics, but also adds to the reliability and simplicity of a digital system.
Quick pull down of room temperature and quick adjustment to demands are essential for customer comfort. Because Digital Scroll can provide transition from 100% capacity to 10% capacity or vise versa instantaneously by changing the loaded and unloaded cycle time, it can react much faster to the changes in system demand without having to pass through intermediate speed changes as required in the inverter systems.
Reliability of system and electronics is an issue in developing markets in Asia. In an inverter system, the electronics is typically complicated. Exposing this complex electronic system to uncertainties of installation and extreme weather conditions results in reliability issues.
The situation is made more complicated by using various bypasses – hot gas bypass and liquid bypass. We will discuss bypass shortly, but the bottom line is that complex systems have a higher probability of failure. The Digital Scroll system is fundamentally simple. Figure on the right shows the typical electronics for the outdoor unit controller.
Hot gas bypass and liquid bypass are used in most of the current technology options valuable. These protection devices are required because the compressor is not able to go down to very low capacities. The Digital Scroll can go down to as low as 10% capacity, so these bypasses are not required. This results in cost savings and system simplicity.
Smaller footprint leads to lower material cost, packaging, storage and shipping costs. Because of its simplicity, a Digital Scroll system can be designed in such a way that it can be more compact and the savings in space can be as much as 30% over present technology options.
The 2 challenges commonly faced by an HVAC engineer are:
Improving EER/COP of the A/C System
Meet heating capacity needs with the best possible efficiency particularly at low ambient conditions
The Digital Scroll Heating technology – that uses the enhanced vapor injection principle, addresses the long overdue need of efficient heating solution. This technology is able to deliver the additional heat at low ambient conditions in the most efficient manner and also allows the heat pump to operate at very low ambient (up to -20°C). This has been made possible by the extension of the scroll compressor safe operating envelope by the vapour injection technology.
The
beauty of this technology is its
inherent simplicity. The standard
Copeland Scroll has a unique feature
called axial compliance. This allows
the fixed scroll to move in the
axial direction, by very small
amounts, to ensure that the fixed
and orbiting scrolls are always
loaded together with the optimal
force.
This optimal force, which holds the
2 Scrolls together at all operating
conditions, ensures high efficiency
of Copeland Scrolls. The Digital
Scroll operation builds on this
principle.
The Digital Scroll operates in two
stages - the "loaded state", when
the solenoid valve is normally
closed and "unloaded state", when
the solenoid valve is open. During
the loaded state, the compressor
operates like a standard scroll and
delivers full capacity and mass
flow. However, during the unloaded
state, there is no capacity and no
mass flow through the compressor.
At this
stage, let us introduce the concept
of a cycle time. A cycle time
consists of a "Loaded State" time,
and "Unloaded State" time (Figure
2).. The duration of these 2-time
segments determine the capacity
modulation of the compressor.
Example: In a 20-second cycle time,
if the loaded state time is 10
seconds and the unloaded state time
is 10 seconds, the compressor
modulation is (10 seconds x 100% +
10 seconds x 0%)/ 20 = 50% (Figure
3). If for the same cycle time, the
loaded state time is 15 seconds and
the unloaded state time is 5
seconds, the compressor modulation
is 75%. The capacity is a time
averaged summation of the loaded
state and unloaded state. By varying
the loaded state time and unloaded
state time, any capacity (10%-100%)
can be delivered by the compressor.
This course provides a comprehensive introduction on Copeland Digital Scroll air-conditioning technology, including key technical and application principles. Highlights include fundamental benefits of the Digital Scroll system over other similar technologies, especially in terms of reliability. Additionally, this course includes a DVD that highlights and further clarifies main points and key lessons from the course.
Dealers and Installers
OEM's Sales Engineers
Design Institute Engineers
Building Owners (especially for tender interviews)
Introduction to Emerson and Copeland
History of the Digital Scroll
Detailed description and explanation of the Digital Scroll technology
Benefits of the Digital Scroll
Comparison between 3 types of VRF technologies
Awards the Digital Scroll has received
Proven successes of the Digital Scroll System
PowerPoint Presentation
Training Manual
Digital Scroll Technology DVD
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