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7.
Important Refrigeration Components
7.1.
Variable Capacity Compressor Features
As the leader in variable capacity compressor technology in the data center industry responding
to environmental and energy challenges, Data Aire developed the gForce Ultra variable capacity
compressor CRAC unit. The quest for greater energy efficiency is continuous; efficiency
benchmarks are always moving up. That’s why Data Aire has moved toward variable capacity
compressor technology for quieter, more energy-saving performance. The compressor
technology uses a brushless Interior Permanent Magnet (IPM) design to provide higher
efficiency. It delivers efficiency across a wider range. A cooling solution optimized for energy
consumption and for power grid requirements. Thanks to a 4:1 modulation ratio, the gForce Ultra
can cycle from 25 to 100 RPS to provide greater savings.
Conventional compressors are designed to run at fixed speed to handle a given capacity
requirement. But in data center applications, the capacity requirement varies. In these
situations, a fixed speed compressor uses various capacity-regulation techniques and can be
less efficient than a compressor utilizing variable capacity technology. A variable capacity
compressor (VCC), on the other hand, saves energy and operates more quietly by varying speed
to match the workload. Tests with VCC compressors have shown an immediate energy savings
and sound level reductions.
Match exactly your cooling requirements to control temperature and humidity, critical for the best
process as well as product quality.
7.2.
Oil Management
Insufficient oil level can be the result of oil depositing itself in pipes and heat exchangers. The
oil deposit can be returned to the crankcase by increasing velocity for short periods, at regular
time intervals or when the velocity is too low to ensure adequate oil return.
With oil return management functions that are built into the control system, these two oil return
mechanisms can be programmed in the variable frequency drive (VFD).
With the oil return management function enabled, the VFD performs oil return by boosting the
com- pressor speed to an appropriate RPM for a selectable duration as programmed into the
VFD parameters. This boost is performed at programmable fixed time intervals or if the
compressor speed has been less than 3000 RPM (50 RPS) for too long which is again a
programmable parameter, whichever comes first. Therefore the maximum time between two
consecutive oil return boosts is fully programmable.
7.3.
Crankcase Heaters
A crankcase heater will minimize refrigerant migration caused by the large temperature gradient
be- tween the compressor and the remainder of the systems. When the compressor is idle, the
oil temperature in the sump of the compressor must be maintained at no lower than
the 10⁰ F (-
12.2
C) above the saturation temperature of the refrigerant on the low-pressure side. This
ensures that liquid refrigerant is not accumulating in the sump.