Emerson Vilter Vission 20/20, Operation And Service Manual

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25 – 2
Section 25 • Cool Compression Control
Vission 20/20 • Operation and Service Manual • Emerson • 35391SC 2.7
in the Oil Pump and Oil Cooling sections, selected au-
tomatically. It will also enable Superheat Monitoring
on the screen.
• As previously described, Cool Compression
compressor does not have an oil pump. Instead
it has a suction oil injection solenoid to pro-
vide oil and liquid ammonia for lubrication and
cooling.
• Cool Compression liquid injection 1 and liq-
uid injection 2 outputs will operate as high / low
pressure ratio solenoid outputs.
Control Functions
In the Compressor Control Menu, special cool compres-
sion control functions are now available, see Figure 25-2.
Auto Load
• Auto load operation will force the compressor to load
to a minimum value once the compressor has started.
By loading the compressor to a minimum value, and
maintaining this capacity, a pressure ratio is created
across the compressor, to ensure its adequate lubri-
cation, and also so that the compressor does not ex-
perience high discharge superheat conditions. Since
compressor lubrication is of great importance, all
load limiting is disabled when auto load is engaged.
• Auto Load at Start
• Defines the value at which Compressor (ca -
pacity slide) should be loaded (and maintained)
at start if Auto Load is enabled.
• Auto Load Timer
• This timer defines the maximum time that
the Auto Load operation will be engaged. After
the timer expires, Auto Load will be disengaged.
• Auto load will be disengaged when one of the
Figure 25-2. Compressor Control Screen - Cool Compression Control (Page 2)