Digital Compressor Retrofit Applications; Reasons To Retrofit; Retrofit Applications To Avoid; Performance Modeling - Emerson Copeland Scroll Digital ZPD34 Bulletin

conditions. This places demanding requirements
on the flow control device to control refrigerant flow
and superheat all the way down to 10% of full load.
Throughout the operating range of the unit, the
suction superheat must remain positive. If the
flow control device is unable to maintain superheat,
an electronic expansion valve, accumulator, or other
means must be taken to maintain at least 20°F of
compressor sump superheat.
Operating Envelope Test
System testing should consist of unit/system operation
at abnormal operating conditions to verify that suction
superheat and compressor discharge temperatures stay
in a range that is healthy for the compressor and tripping
of the compressor overload is avoided. Please consult
with application engineering for recommended tests and
analysis of test data.

DIGITAL COMPRESSOR RETROFIT APPLICATIONS

Reasons To Retrofit

There are a number of reasons why retrofitting a non-
modulating system to one that modulates will benefit
the building owner and its occupants. Some of these
reasons include:
1. Reduced indoor temperature and humidity swings
2. Reduced power consumption and operating costs
3. Reduced cyclic losses
4. Qualification for special utility rebates
Applications that have excess cooling capacity and are
single zone, constant or variable air-flow are certainly
in the scope of retrofit opportunities. Units that employ
hot-gas-bypass for capacity control are also ideal units
for a digital scroll retrofit.

Retrofit Applications To Avoid

NOTICE
Always check with the original equipment
manufacturer, before modifying the equipment,
to understand their warranty policies regarding
equipment modifications.
The success of the retrofit will depend on the amount
of planning and evaluation done before the retrofit.
Applications such as clean rooms for manufacturing
sensitive components, laboratories, hospital operating
and recovery rooms, and equipment rooms that require
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constant cooling are all applications that would benefit
from a modulating digital scroll. Many of these are
critical cooling applications and require equipment that
is designed specifically for these applications. Don't
attempt to retrofit a non-modulating HVAC unit, in a
critical application, to one with a digital scroll in an attempt
to make the unit perform well beyond its intended use.
Applications that have complex refrigeration circuits
(modulating reheat, heat recovery for water heating,
etc.) should not be considered for a digital scroll retrofit.

Performance Modeling

NOTICE
Emerson Climate Technologies, Inc. is not
responsible or liable for incorrect energy use
predictions.
Successful digital scroll retrofit projects, and resultant
energy savings, have been documented by several
industry energy groups. Predicting the energy usage
and calculating a return on investment before the
project is undertaken is not trivial and is best done by
experienced companies that use advanced software
programs to predict energy use. Before large retrofit
projects are considered, as much front-end analysis
as possible should be done to better predict how much
energy might be saved. Tabular performance data and
the ten coefficients for the AHRI polynomial equation for
performance at 50% and 100% load are available for
modeling purposes in the Online Product Information
(OPI) section at EmersonClimate.com.

System Modifications

NOTICE
Always check with the OEM of the equipment being
considered for the digital scroll retrofit, before the
retrofit is undertaken. The OEM may have specific
instructions developed that offer step by step
guidance.
Before beginning the retrofit, the system should be
operable and system operating conditions should be
logged for future reference. The compressor suction
and discharge pressures, suction superheat, subcooling,
volts, amps, evaporator air flow and leaving temperature,
and system charge should all be measured and recorded
prior to any system modifications.
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