APPLICATION GUIDELINES
30
FRCC.PC.007.B5.02
SYSTEM DESIGN RECOMMENDATIONS
Off -cycle migration Off -cycle refrigerant migration is likely to occur
when the compressor is located at the coldest
part of the installation, when the system uses a
bleed-type expansion device, or if liquid is al-
lowed to migrate from the evaporator into the
compressor sump by gravity. If too much liquid
refrigerant accumulates in the sump it will satu-
rate the oil and lead to a fl ooded start: when the
compressor starts running again, the refrigerant
evaporates abruptly under the sudden decrease
of the bottom shell pressure, causing the oil to
foam. In extreme situations, this might result
in liquid slugging (liquid entering the scroll ele-
ments), which must be avoided as it causes irre-
versible damage to the compressor.
Performer® SH scroll compressors can tolerate oc-
casional fl ooded starts as long as the total system
charge does not exceed the maximum compres-
sor refrigerant charge.
A suitable test to evaluate the risk of off -cycle mi-
gration is the following:
Stabilize the non running system at 5°C ambi-•
ent temperature,
Raise the ambient temperature to 20°C and •
keep it for 10 minutes,
Start the compressor and monitor sump tem-•
perature, sight glass indication and sound
level.
The presence of liquid in the crankcase can be eas-
ily detected by checking the sump level through
the oil sight glass. Foam in the oil sump indicates
a fl ooded start.
A noisy start, oil loss from the sump and sump cool
down are indications for migration. Depending
on the amount of migration graduate measures
shall be taken:
Sump heater•
Liquid line solenoid valve•
Pump down cycle•
More detailed information can be found in the paragraphs hereafter.
Please contact Danfoss Technical Support for any deviation from these guidelines.
BELOW charge limit ABOVE charge limit
Cooling only systems,
Packaged units
No test or additional safeties required
Refrigerant migration & fl ood back test
Sump heater
Cooling only systems
with remote condenser
and split system units
Refrigerant migration & fl ood back test
Sump heater
Refrigerant migration & fl ood back test
Sump heater
Liquid receiver (in association with LLSV and
pump down)
Reversible heat pump system
Specifi c tests for repetitive fl ood back
Sump heater
Defrost test For more details, refer to section "Reversible heat pump system"
Recommended Required No test or additional safeties required
Note: for special conditions such as low ambient temperature, low refrigerant load or brazed plate heat exchangers please refer to
corresponding sections.
REC
REC
REQ
REQ
REQ
REQ
REQ
REQ
REQ
REQ
REC
REC
9
9
To Next Page
Loading...
Need help?
General
