Application Engineering |
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Modulation Control
Two different controls are available from Emerson to provide digital scroll modulation control, the Copeland Scroll™ Digital Compressor Controller and the Emerson Commercial Comfort Controller.
The Copeland Scroll™ Digital Compressor Controller is an open loop controller that provides control, protection, and diagnostics for the digital scroll and is suited for OEM applications. The system controller supplied by the OEM calculates the required compressor capacity and communicates that capacity to the digital scroll controller via a
The Emerson Commercial Comfort Controller is a closed loop controller that provides modulation control based on space temperature and is suited for both OEM and retrofit applications. This controller is typically located in the conditioned space and controls the modulation cycle of the compressor without the need for an additional system controller. For more information on the Emerson Commercial Comfort Controller, please refer to
NOTICE
For OEMs that choose their own controls package, the controls must include the protection features incorporated into the Copeland Scroll™ Digital Compressor Controller. Please consult with Application Engineering for a list of these requirements.
APPLICATION TESTS
Oil Level Verification
If the system configuration is more complex than a single circuit packaged system with one compressor, evaporator, and condenser, an oil return test is highly recommended during system development testing. For this test a sample compressor with a
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If the system contains more than 20 pounds (9 kg) of refrigerant, it is our recommendation to add one fluid ounce of additional oil for every 5 pounds (15 ml/kg) of refrigerant over this amount. This is a starting point and oil should be added as determined through system testing or as required by the end use application in the field.
The compressor oil level should be checked with the compressor "off" to avoid the sump turbulence when the compressor is running. Manifolded compressors should have their oil levels checked after 20 to 30 seconds of off time, to allow oil balancing between the manifolded compressors.
Excessive Liquid Flood Back Tests
It is expected that the design will not flood during operation at all of the varying loaded and modulation 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
The operating envelopes and recommended modulation ranges are shown in Figures 4 and 5. System testing must be performed if operation outside of these recommended ranges is desired. 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