GENER
AL INFORMA
TION
PR
ODUC
T INFORMA
TION
SY
STEM DESIGN
INTEGR
ATION INT
O SY
STEM
ORDERING INFORMA
TION
Manage off cycle migration
R
Requirement
System evaluation
Off -cycle refrigerant migration happens:
•
when the compressor is located at the coldest
part of the installation, refrigerant vapor
condenses in the compressor.
•
or directly in liquid-phase by gravity or pressure
difference.
When the compressor restarts, the refrigerant
diluted in the oil, or stored in evaporator,
generates poor lubrication conditions, and may
reduce bearings life time. In extreme situations,
this leads to liquid slugging that can damage the
compressor scroll set.
· Compressor can tolerate occasional flooded
start, but it should remain exceptional situation
and unit design must prevent that this situation
from happening at each start.
· Right after start, liquid refrigerant must not flow
massively to compressor.
· The charge limit is a threshold beyond with
some protective measures must be taken to
limit risk of liquid slugging and extreme dilution
at start.
Use the table below in relation with the system
charge and the application to quickly define
necessary safeties to implement.
Charge limit is defined in table below:
Models
Refrigerant charge limit
(kg / lb)
Single
VZH052-065
5.4 / 12
Application
BELOW charge limit
ABOVE charge limit
All
Ensure tightness between condenser & evaporator when system is OFF
• Thermostatic expansion Valve (TXV), Liquid Line Solenoid Valve LLSV** strongly
recommended
• Electronic expansion valve (EXV) must close when system stops including in power shut
down situation
Non split
No test or additional safeties required
• Belt type heater*
• External Non-Return Valve
Split
Since each installation is unique, refrigerant charge may vary
• Belt type heater*
• Liquid Line Solenoid Valve**+ pump-down cycle***
• External Non-Return Valve
SY
STEM DESIGN
30
AB237586440343en-000601