AGL_Ref_ST_ZO_E_Rev00
7
Please note the following considerations about operating envelopes:
▪
Before compressor start with the matched pair of ZOV*AG and the EVM/EVH drive, the pressure
difference in the system has to be below 25 bar. If the pressure difference is reduced by opening
the expansion valve, care must be taken to avoid liquid floodback to the compressor
– also see
section 3.11 "Suction line accumulator"
.
▪
An oil return test for the system must be performed. If required, the system design should be
improved to ensure sufficient oil return from the system to the compressor
– also see
section
5.16 "Oil level"
.
▪
At start-up the system should be able to bring the compressor to a point inside the envelope as
fast as possible and to keep the compressor running there. Running outside the envelope is not
allowed.
▪
Running/oscillating the compressor in and out of the envelope borders is not allowed and should
be avoided.
▪
Running the compressor below the envelope at low condensing temperatures is possible for no
longer than 30 minutes but the user must be aware that unloading noise from the compressor can
occur. In this area the speed limits according to the evaporating temperatures in the envelope
should be respected.
▪
The qualified application envelopes will change with the compressor speed. At all operating
conditions the minimum and maximum speed limits according to
Figure 5
have to be respected.
With changing operating conditions the speed limits have to be determined by linear interpolation
between the limits given in
Figure 5
– also see speed limits animation in Select software available
▪
Fast speed changes can cause instable control, eg, on the superheat control. Per Emerson
experience speed changes should be not higher than approximately 200 rpm/s depending on the
system reaction.
▪
The user should adequately take care of controlling the envelope.
▪
To stop the compressor, see
Figure 6
"Controlled shutdown".
Figure 6: Controlled shutdown and ramp-up
NOTE: Emerson iProRACK controller series 5 offers all required features to operate the
ZO(V)*AG scroll compressors in the low temperature stage of a booster system.
NOTE: Before first start, each drive has to be configured according to the compressor model.
NOTE: The EVM/EVH drive overload protection aims at protecting the drive and the
compressor. It cannot be used in the system as an operating envelope limitation. For more
details on the overload protection refer to
the EVM/EVH User Manual.
NOTE: Paralleling of variable-speed ZOV*AG compressors with fixed-speed ZO*AG models is
possible.
