Variable Speed Compressor; Features; Oil Management; Crankcase Heaters - Data Aire gForce Ultra Installation, Operation And Maintenance Manual

7.

Variable Speed Compressor

7.1

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 com-
pressor CRAC unit. The compressor technology uses a brushless Interior Permanent Magnet (IPM)
design to provide higher efficiency. And 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.
Match exactly your cooling requirements to control temperature and humidity, critical for the best pro-
cess 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 inter-
vals 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 mech-
anisms 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 param-
eters. 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 program-
mable.
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 tem-
perature in the sump of the compressor must be maintained at no lower than the 10⁰ F above the
saturation temperature of the refrigerant on the low pressure side. This ensures that liquid refrigerant
is not accumulating in the sump.
7.4

Oil Level

When the compressor is running under stable conditions the oil level must be visible in the sight glass.
The presence of foam filling the sight glass indicates large concentration of refrigerant in the oil and/or
presence of liquid returning to the compressor. The oil level can also be checked a few minutes after
the compressor is shut down, the level must be between ¼ and ¾ of the sight glass. When the com-
pressor is OFF, the level in the sight glass can be influenced by the presence of refrigerant in the oil.
Always use original Danfoss POE oil 160SZ from new cans. Top-up the oil while the compressor is
at idle. Use a Schrader connector or any other accessible connector on the compressor suction line
and a suitable pump.
7.5

VFD Drive

There are tremendous energy saving and application advantages available by applying a VFD drive
54