Copeland Discus 2D, 3D and 8D Semi-Hermetic Compressors

Overview

The Copeland Discus semi-hermetic compressors are reciprocating compressors for commercial and industrial refrigeration, built around Copeland’s Discus valve plate design. The application guidelines covered here describe the 2D*, 3D* and 8D* models, with 2, 3 and 8 cylinders respectively and displacements from 16.8 to 181 m³/h. Copeland states that the optimised valve plate design of these compressors provides the highest energy efficiency, and the compressors are used as single units, in condensing units or in multi-compressor racks. The 4-cylinder and 6-cylinder Stream models are covered by a separate Copeland manual.

Seven Star LLC supplies Copeland Discus compressors, accessories and replacement parts to refrigeration contractors, cold store operators and food producers in the Sultanate of Oman and across the GCC. Discus compressors such as the 3D and 8D families have a long service history in supermarkets, cold rooms, ice plants and process cooling across the region, so like-for-like replacement is a frequent requirement. With engineering support in Muscat, our team helps confirm model, motor version and design revision before supply.

Operating Principle

In general terms, a semi-hermetic reciprocating compressor uses a crankshaft driven by a built-in electric motor to move pistons in their cylinders, with suction and discharge valves in the valve plate controlling the flow of refrigerant vapour. The Copeland Discus design uses Discus valve plates, and in these compressors the complete cylinder head is under discharge pressure. The 2D*, 3D* and 8D* models are suction-gas cooled: incoming refrigerant passes over the motor before it reaches the cylinders, and an additional head fan may be required depending on operating conditions, as determined in the Copeland Select software.

Lubrication on the Copeland Discus models is by an external oil pump that always works in the correct direction regardless of the direction of rotation, with normal oil pressure 1.05 to 4.2 bar above crankcase pressure. The pump accommodates an OPS2 oil safety system or a conventional oil pressure switch. Oil returns with the suction gas through a suction strainer, separates in the motor chamber and reaches the crankcase through a relief valve that reduces foaming at start-up. For these models Copeland specifies a minimum stable suction superheat of at least 10 K for a typical evaporator and expansion valve configuration.

Engineering Design of the Copeland Discus 2D, 3D and 8D

The Copeland Discus 2D*, 3D* and 8D* compressors have been upgraded internally for A2L refrigerants. New design revision numbers identify the approved models: 2D*4, 3D*6 and 8D*7 are approved for A2L and A1 refrigerants, while the older 2D*3, 3D*5 and 8D*6 revisions are qualified for A1 refrigerants only. The change applies from serial number 23B, production date February 2023. Maximum allowable pressure PS is 32.5 bar(g) on the high-pressure side and 22.5 bar(g) on the low-pressure side, and each cylinder head has a 1/8 inch NPTF tapped hole for a high-pressure switch.

Options for the Copeland Discus range include Demand Cooling liquid injection for 2D* and 3D* low temperature duties with refrigerants such as R448A, R449A, R407A and R407F, using a cylinder head temperature sensor, an electronic driver and an injection valve. Unloaded start for part-winding or star-delta starting is provided by an external by-pass kit with a solenoid valve on 2D* and 3D* models and by an internal special cylinder head on 8D* models. Mechanical blocked-suction capacity control is available on 8D* compressors, with a first step of 25% and a second step of 50%.

Key Features

The Copeland application guidelines describe the following key features of the Copeland Discus 2D, 3D and 8D models.

• Two-, three- and eight-cylinder models cover displacements from 16.8 to 181 m³/h.
• Discus valve plates provide high energy efficiency in refrigeration duty.
• A1 refrigerants R448A, R449A, R407A, R407F, R404A, R407C, R513A, R450A, R134a and R22 are qualified.
• New design revisions 2D*4, 3D*6 and 8D*7 are also approved for R454C, R455A and R454A.
• Suction-gas cooling of the motor keeps the design compact and efficient.
• The external oil pump works in either rotation direction and accepts OPS2 or a conventional oil pressure switch.
• Demand Cooling liquid injection protects 2D* and 3D* models in low temperature applications.
• Unloaded start and, on 8D* models, 25% and 50% blocked suction capacity control are available.

Industrial Applications

The Copeland Discus range is used in medium and low temperature refrigeration: walk-in cold rooms and freezer rooms, supermarket racks and remote display cases, ice making, blast freezing, fish and meat processing, dairy plants, cold chain logistics and industrial process cooling. The 8D* models suit larger racks and central plants, while 2D* and 3D* models fit condensing units and smaller systems. In Oman’s hot climate, high condensing temperatures make correct selection in Copeland Select, condenser sizing, head cooling and Demand Cooling important for reliable operation.

Seven Star LLC supplies the Copeland Discus range together with existing models on our site such as the Copeland D3DS5-1500-AWM/D semi-hermetic compressor and the DWM Copeland D8SJ1-600X semi-hermetic compressor, as well as scroll compressors such as the Copeland ZR250KCE-TED-522 scroll compressor. Our team in Muscat supports contractors in Oman and the GCC with selection, replacement and accessories.

Technical Specifications

The table summarises Copeland Discus 2D*, 3D* and 8D* data from the Copeland application guidelines; capacity data per model are available in Copeland Select.

How to Order

To order a Copeland Discus compressor, send Seven Star LLC the full model code, motor version and serial number from the nameplate, or the refrigerant, capacity and operating conditions for a new system. Our refrigeration team in Muscat will confirm the selection and design revision, share the technical documentation for download and prepare a formal quotation. Seven Star LLC supplies Copeland compressors to customers in Oman and the GCC with engineering support.