Danfoss DSH090 Application Manual page 49

Scroll compressors, DSH090 to DSH600 | Application
Test, criteria and solutions
Table 30: Test, criteria and solutions
Test Purpose Test condition
Liquid flood Steady-state
A
back test
Liquid flood back testing must be carried out under expansion
valve threshold operating conditions:
• Lowest foreseeable evaporation, and highest foreseeable
• Minimum number of compressor running.
For reversible system, perform test in both heating and cooling
mode.
Transient Tests must be carried out with most unfavorable conditions :
• fan staging,
• compressor staging
• ...
Defrost test Check liquid Defrost test must be carried out in the most unfavorable condi-
floodback dur- tions (at 0°C (32°F) evaporating temperature).
ing defrost cy-
cle
(1) (1)
Suction accumulator offers protection by trapping the liquid refrigerant upstream from the compressor. The accumulator should be sized at Suction accumulator offers protection by trapping the liquid refrigerant upstream from the compressor. The accumulator should be sized at
least 50 % of the total system charge. Suction accumulator dimensions can impact oil return (gas velocity, oil return hole size...), therefore oil least 50 % of the total system charge. Suction accumulator dimensions can impact oil return (gas velocity, oil return hole size...), therefore oil
return has to be checked according to section return has to be checked according to section
Placing oil temperature sensor
Oil temperature sensor must be placed on the bottom of the baseplate. Some thermal paste shall be used to
improve the conductivity. The sensor must also be correctly thermally insulated from the ambiance.
The Oil superheat is defined as: (Oil temperature - Evaporating temperature)
Figure 53: Placing oil temperature sensor
1
© Danfoss | Climate Solutions | 2022.10
condensation.
Manage oil in the Manage oil in the
1 Oil temperature sensor must be placed on the bottom of the baseplate.
Pass criteria
Suction superheat >5K (9°F)
and the oil superheat shall not
be more than 60 sec below the
safe limit defined in the Dilu-
tion Chart. (see
DSH090 to DSH184
Oil superheat shall not be more
than 60 sec per hour below the
safe limit defined in the Dilu-
tion Chart. (see
DSH090 to DSH184 R452B /
R454B)
Oil superheat shall not be more
than 60 sec per hour below the
safe limit defined in the Dilu-
tion Chart. (see
DSH240 to DSH600 R410A/
R452B / R454B)
circuit. circuit.
Solutions
1. Check expansion valve se-
lection and setting.
◦ For Thermostatic ex-
pansion valve (TXV)
Dilution Chart -
check bulb position...
R410A)
◦ For Electronic expan-
sion valve (EXV) check
measurement chain
and PID....
2. Add a suction accumulator
(1)
Dilution Chart -
1. Check defrost logic. In re-
versible systems, the de-
frost logic can be worked
Dilution Chart -
out to limit liquid flood-
back effect. (for more de-
tails see Control logic).
2. Add a suction accumulator
(1)
AB288965961751en-001402 | 49