Copeland Stream 4MTL CO2 Semi-Hermetic Compressor

Overview

The Copeland Stream 4MTL is a series of four-cylinder semi-hermetic reciprocating compressors engineered for R744 (carbon dioxide) refrigeration in transcritical service. Copeland designed the range for medium-temperature duty in CO2 booster and cascade systems, with a design pressure of 135 bar and optimised refrigerant flow and heat transfer for high efficiency. Nine displacements, from the 5 hp 4MTL-05 to the 50 hp 4MTL-50, cover cooling capacities from 8.8 kW to 67.8 kW at EN12900 rating conditions, so the Copeland Stream 4MTL can be used singly in condensing units or in parallel on large supermarket and cold-storage racks.

Seven Star LLC supplies Copeland Stream 4MTL compressors to refrigeration contractors, rack builders and facility owners in Oman and across the GCC, with engineering support in Muscat. As regional retailers and food logistics operators move away from high-GWP HFC refrigerants, we help customers select the right model, electronics options and spare parts for natural-refrigerant projects.

Working Principle

In a transcritical CO2 cycle, the Copeland Stream 4MTL compresses suction vapour from the medium-temperature evaporators to a discharge pressure above the critical point of carbon dioxide (about 31°C and 73.8 bar). Heat is then rejected in a gas cooler rather than a conventional condenser, and the high-pressure gas is expanded through a high-pressure valve into a flash tank. Copeland rates the 4MTL range at an evaporating temperature of −10°C, gas cooler exit of 35°C at 90 bar and 10 K suction superheat, which reflects typical warm-climate operation where the system runs transcritical for most of the year.

Inside the Copeland Stream 4MTL, four pistons driven by a crankshaft draw gas through suction valves and push it out through discharge valves, while an oil splasher system keeps bearings and cylinders lubricated at both constant and variable speed. The semi-hermetic construction places the motor inside the refrigerant-tight housing, cooled by suction gas, while bolted covers allow valve plates and other components to be serviced. Capacity can be modulated steplessly with an inverter between 25 and 70 Hz, matching compressor output to the actual cabinet and cold-room load and reducing on/off cycling.

Engineering Design of the Copeland Stream 4MTL

CO2 systems operate at pressures several times higher than HFC plants, and the Copeland Stream 4MTL is built for that duty. The compressor housing is designed for 135 bar on the high side, and Copeland specifies a standstill pressure capability of 90 bar on the low side, which allows the system to ride through a power outage without venting refrigerant. An integrated high-pressure relief valve protects the compressor itself, and discharge temperature protection guards against overheating at high pressure ratios. All models carry Copeland compressor electronics technology, which monitors operating conditions and allows system-related problems to be diagnosed faster, or even before they occur.

Practical installation details of the Copeland Stream 4MTL are aimed at pack builders. Service valves can be rotated through 360° to simplify discharge and suction piping, two sight glass positions are provided for mounting oil management controls and for visual inspection, a further sight glass allows oil level to be checked while running, and an oil port supports oil equalisation between compressors in parallel systems. The 4MTL range is built in three body sizes: 4MTL-05 to -09, 4MTL-12 to -30, and 4MTL-35 to -50, with net weights of about 123 kg, 170 to 175 kg and 264 to 276 kg respectively. Standard electrical supply is 380–420 V, three phase, 50 Hz.

Key Features

The Copeland Stream 4MTL range combines the following features for CO2 refrigeration plants:

• Nine models from 5 hp to 50 hp provide 8.8 to 67.8 kW of medium-temperature cooling capacity at EN12900 R744 conditions.
• The 135 bar design pressure on the high side suits transcritical operation in hot ambient conditions.
• A 90 bar suction standstill pressure capability helps the system keep its charge during power outages.
• Inverter operation from 25 to 70 Hz gives stepless capacity modulation and tighter suction pressure control.
• Copeland compressor electronics provide diagnostics and protection to detect system problems early.
• An integrated high-pressure relief valve and discharge temperature protection guard the compressor.
• Service valves rotate 360°, and three sight glasses plus an oil equalisation port simplify parallel rack design.
• An oil splasher lubrication system keeps the running gear lubricated at both fixed and variable speed.

Industrial Applications

The primary market for the Copeland Stream 4MTL is commercial refrigeration in CO2 booster systems, where it serves the medium-temperature suction group for chilled display cases, dairy and produce cabinets and cold rooms. Copeland notes that using transcritical-rated compressors on both the medium-temperature side and the low-temperature subcritical side gives the system full resilience in case of power outage. The same compressors suit central plants for hypermarkets, distribution centres, food processing plants and hotel or hospital kitchens, where natural refrigerants reduce regulatory exposure to HFC phase-down.

In Oman and the wider GCC, the long hours of high ambient temperature mean that CO2 systems spend much of the year in transcritical mode, which makes the 135 bar rating and accurate high-side control important. Seven Star LLC supplies the Copeland Stream 4MTL with engineering support in Muscat, supporting contractors building racks for retail chains, cold stores in the Sohar and Salalah logistics zones and food processors who are planning a move to R744.

Technical Specifications

The following Copeland Stream 4MTL data is taken from the manufacturer brochure at EN12900 R744 conditions: evaporating −10°C, gas cooler exit 35°C at 90 bar, superheat 10 K.

How to Order

To specify a Copeland Stream 4MTL compressor for a new CO2 rack or a replacement, send Seven Star LLC an RFQ with the model, system design and operating conditions. Our refrigeration team confirms current availability and lead time, provides the Copeland brochure attached to this page as the Copeland Stream 4MTL datasheet reference and can quote related items such as the Alfa Laval M6 plate heat exchanger, the DWM Copeland D8SJ1-600X semi-hermetic compressor for HFC plants, or refrigeration controls like the Alco 240RA refrigerant solenoid valve. Seven Star LLC is a trusted supplier offering engineering support in Muscat to customers throughout Oman and the GCC.