Crankcase heater
The crankcase heaters are designed to protect the compressor against o-c ycle migration of refrigerant.
For DSH090-105-120-140-161-184, the surface sump heater is located on the compressor shell. For better standby
energy consumption, Danfoss provides 48W and 80W two optional surface sump heater. The selection of surface
sump heater could be refered to Table 32: Surface sump selection principle
Figure 57: DSH090 to 184
Table 32: Surface sump selection principle
Compressor Surrounding Ambient
Unit has enclosure, no wind
Unit has no enclosure, with wind
Unit has no enclosure, wind >5m/s (ft/s)& ambient temperature <-5°C
80W SSH + additional SSH/thermal insulation
For DSH240-295-381-485-600, the use of 75W crankcase heater is recommended.
Figure 58: DSH240 to DSH600
The heater must be turned on whenever all the compressors are o. Crankcase heater accessories are available from
Danfoss (see section Accessories and Spare parts).
Liquid line solenoid valve (LLSV)
A Liquid line solenoid valve (LLSV) is used to isolate the liquid charge on the condenser side, thereby preventing
against charge transfer to the compressor during o -cycles. The quantity of refrigerant on the low-pressure side of
the system can be further reduced by using a pump down cycle in association with the LLSV.
Pump-down cycle
By decreasing pressure in the sump, pump down system:
• evacuates refrigerant from oil
• set the sump saturating pressure much lower than ambiance temperature and due to that, avoid refrigerant
condensation in the compressor.
Pump-down must be set higher than 1.7bar(g) (25 psig). For more details on pump-down cycle see section Control
logic.
Scroll compressors, DSH090 to DSH600 | Application
© Danfoss | Climate Solutions | 2022.10 AB288965961751en-001402 | 52
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