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Chapter 1. Complete Condensing Units with Scroll or Piston Compressors - Freedom of choice
Several factors are involved in deciding whether scroll technology or piston technology is the best choice for a particular refrigeration system. In some cases a scroll compressor is unbeatable, while in other cases a piston compressor is top. Danfoss offers a range of complete condensing units with a choice of compressor technologies: in addition to the existing series with piston technology, which is currently being expanded, Optyma PlusTM now includes the brand-new MLZ series of scroll compressors for refrigeration systems.
The Optyma PlusTM family
Piston technology: reliable and robust
Condensing units with piston compressors are a familiar sight in refrigeration systems. Thanks to their broad range of applications and the multi refrigerant compatibility of many models, they are extremely versatile. In addition, this technology has proven its reliability over many years. Optyma PlusTM complete condensing units are specifically designed for use in cold rooms and freezer rooms, beer and wine cellars, small grocery shops and minimarkets, and filling station shops.
Additional capacities available
With the introduction of new models in the Optyma PlusTM line with especially low and high cooling capacity, Danfoss is maintaining its strategy of the highest possible degree of hermetic construction. Consequently the new condenser units, which are fully equipped with a sight glass, filter drier, two ball shut-off valves, a fully configured electrical cabinet, pressure switch. fan speed control and external main switch, also have hermetic piston compressors. The new range of models offers ideal stand-alone solutions for applications such as single cooling cabinets in filling station shops. They can now be used in systems rated at 1 kW or more under standard coldroom conditions. For especially large cold rooms, double-fan models with capacities up to 20 kW at an evaporating temperature of -10 °C are also available now.
Chapter 2. Scroll technology: progressive with low vibration
Optyma PlusTM condensing units with scroll technology were first presented on the occasion of Chillventa 2008 as design studies. Thanks to the large number of positive responses and constructive feedback from expert visitors, this product could be optimised for practical use and tailored to the operational requirements of refrigeration compartments before the start of regular production. This positive customer response gave the go-ahead for introducing a separate product line with scroll technology. Advanced compressor technology in the form of the brand-new MLZ refrigeration scroll compressors forms the heart of these fully dressed condensing units. Their special features include low-vibration operation and low noise levels. The weight of the MLZ compressors is distinctly lower than average. This makes them easier to handle and reduces transport costs. The slim, tall form factor of the MLZ scroll compressors also allows the structure of these fully equipped condensing units to be made more compact.
Lower power consumption and long plant life
An energy-efficient motor and a scroll geometry specifically optimised for refrigeration applications combine to yield very good efficiency. In a wide variety of system states, such as during the pull-down phase, Danfoss' patented adaptive control system constantly ensures an optimal axial pressure between the scrolls. This prevents leaks and minimises friction.
The MLZ compressor series is specifically designed for long life and reliability. This can be seen from many different design details. For example, the scroll guides (Oldham coupling) have additional reinforcement, high-quality carbon bearings are fitted for the crankshaft, and a patented overload protection device (HOOP) protects the compressor against potential damage from thermal overload.
Optyma PlusTM with scroll compressor (left), MLZ scroll compressor (middle), and MLZ scroll set (right)
Designed for low operating noise and low pulsation
MLZ scroll compressors are designed for low noise generation. Extremely low-noise, vibration-free operation is achieved by the combination of low-friction permanent sealing of the scroll set, the absence of suction and pressure valves, press-fit assembly, and flow-optimised check valves. In the Optyma PlusTM units, these compressors are additionally fitted in a closed compressor section with sound damping to reduce the noise level to a whisper.
Danfoss scroll compressors have a vertical crankshaft, with the scroll set located above the crankshaft. The scroll set consists of a fixed spiral and an orbiting spiral. The two spirals are interleaved, and they compress the refrigerant by transporting it from the outer edge of the scroll set to the centre with an orbital motion. With this operating principle, gas at various compression levels is always present during the compression process due to the different-sized "pockets" where compression actually occurs. Scroll compressors expel relatively small amounts of refrigerant at relatively high frequency. This reduces the pulsation level. For fitters, this means that a muffler to dampen pulsation is often unnecessary. Noise problems and pressure switch malfunctions due to pulsation are also less likely in systems with scroll compressors.
Chapter 3. Combined main switch and overcurrent trip
There's more to a fully equipped condensing unit than the compressor. The details are especially important with regard to servicing and suitability for practical use. For instance, the Optyma PlusTM units are fitted with a combined main switch and overcurrent trip. The main switch can be operated externally and switches the unit off (full disconnect). If the condensing unit fakes too much current or the phase currents are not balanced (with three-phase versions), the overcurrent trip is triggered. This has the advantage that it can be clearly seen from outside whether the unit switched off due to overcurrent (switch in the middle "Motor Protection" position) or was switched off manually (switch turned fully to the "Off" position).
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Main switch positions: Off (left) and Overcurrent (right) |
Chapter 4. Fully equipped units with space-saving installation
For many years, the trend has been toward reducing the installation time at the customer site. Aside from reducing the customer's expenses, this yields numerous advantages for installers. Components prefitted in the factory are tested for proper operation and absence of leaks, and it is easier for to estimate the cost of using them than the cost of retrofitting components at the customer site. Inconvenient installation conditions at the customer site can easily lead to unforeseeable delays in component retrofitting, and the costs of such delays cannot be fully estimated in advance. For the reason, the Optyma PlusTM units come fully equipped, including a filter dryer and sight glass with indicator.
Compared with conventional condensing units, Optyma PlusTM units are very slender. This gives them a very compact installation footprint, which means they can be installed nearly everywhere. Wall mounting with installation brackets is also possible. The tall, slender shape also has the advantage that service fitters can make measurements in the integrated electrical cabinet without kneeling.
OptymaTM Control regulation
OptymaTM Control control units
OptymaTM Control (AK-RC 101) control units are a good choice for use with Optyma PlusTM units. They provide all the functions of a traditional refrigerated unit controller, and they are easy to program and install. The control module is built into the electrical enclosure. You only have to attach the unit to the wall and connect the wiring, and then it is ready for use. The large LED display continuously provides system status information, and a front-panel circuit breaker indicates whether everything is OK on the electrical side. The large foil keypad buttons are easy to use and easy to clean. OptymaTM Control units are available in several versions, and they can also be used with other condensing units.
Optyma PlusTM is available in four housing sizes
All Optyma PlusTM condensing units are built using only high-quality Danfoss components and come fully assembled with all necessary tubing and wiring, ready for installation. The expanded product line is available in four different enclosure sizes with the following capacity ranges: 1 to 10 kW for R134a, 1 to 20 kW for cold room applications (MBP) with R404A, 3 to 25 kW for air conditioning systems with R407C (MBP), and 0.5 to 10 kW for freezer applications with R404A (LBP).