15 mm
(0.59
Inch)
1
2
3
4
5
6
7
cc-0048
1
2
3
4
5
6
7
Tightening torque 15 Nm
HM 8 bolt
Lock washer
Flat washer
Steel mounting sleeve
Rubber grommet
Nut
Figure 8: Grommets for VCH115
Max inclination
During operation, the maximum inclination from the vertical plane must not exceed 3 degrees.
System design generalities
Compressor capacity and modulation
Usually, compressors are selected to cover peak load cooling/heating capacities between 70-140 rps.
Modulation
(difference
between minimum speed and maximum speed) is a very important point for unit design.
The larger the modulation number, the challenging the unit design will be. This would consequently increase unit
cost.
The minimum compressor speed must be
defined
according to unit need. It often makes sense to set unit minimum
speed higher than minimum compressor speed
qualified
by Danfoss.
Differences
between variable speed and
fix
in speed unit design
Variable speed compressors were created with state of the art technology with the intent to be
efficient
and
precise. Speed variations have led to challenges that must be addressed by unit design.
Variable speed compressor is a great technology to design
efficient
and precise unit, however, speed variation leads
to challenges that must be addressed by unit design. The
first
challenge is linked to part of the load operation. Unit
design must ensure that oil is returning back to the compressor, even while it is at the lowest speed. The expansion
device must also ensure safe superheat across speed range. The second challenge is due to variation of speed itself.
On the opposite hand, on a variable speed system, compressor speed is permanently changing according to load.
Consequently, expansion valve must adapt quickly enough to guaranty proper superheat control during transient.
Variation of compressor speed can also lead it’s own challenges for vibrations. While in
fix
speed, only one frequency
is excited by the compressor. In variable speed, the whole compressor frequency range may excite the system. The
chance of going through resonant frequency is then more greatly increased. The following chapters give details
advices to integrate variable speed compressor in a unit. Designing a variable speed unit requires to go through all
of them to
define
necessary safeties and
qualifications.
Compressor and
drive control
Superheat Man-
agement
Oil return man-
agement
Operating enve-
lope
compressor Me-
chanical installa-
tion
Sound and vibra-
tions manage-
ment
Drive installation
© Danfoss | Climate Solutions | 2023.08
AB392939083370en-000202 | 17
Scroll compressors, VCH115 | Mechanical connections