T-CU11-OCT22-0
Page 11
Application Guidelines
Figure 7: Piping Diagram for Pump Down System
Suction Accumulator
An accumulator is required if repeated flooded starts could occur, dilute the oil in the compressor causing inadequate
lubrication and bearing wear.
A suction accumulator MUST added at suction line near to compressor for:
i.
System with charge exceed compressor limit.
ii.
Systems with defrost schemes or transient operations that allow prolonged, uncontrolled liquid return to the
compressor.
Suction accumulator may not be required for system with room thermostat control with pump down (solenoid valve
installed at liquid line), with the condition suction header of sufficient volume is made to prevent liquid migration to the
compressor during off cycle.
Disharge Thermostat
The discharge temperature will rise rapidly if the compressor is running under the overload conditions or lack of
refrigerant conditions.
For scroll compressor,
the internal motor protector cannot protect the compressor against all the possible failures.
Thus, it is recommended to install external discharge thermostat located on the discharge line within 100mm (
4”) of the
compressor shell with cut out temperature not exceed 130
0
C. The discharge thermostat should be installed on top side
of the discharge tube and it also important be well insulated.
Crankcase Heaters
The refrigerant is usually gathering in coldest point within the system during OFF cycle and the compressor might
become the right one where most of liquid refrigerant centralized.
Crankcase heater is required when the system charge exceed charge limit and require remain energized during the
compressor off cycles. The initial start in the field is a very critical period for any compressor because all load-bearing
surfaces are new and require a short break-in period to carry high loads under adverse conditions. Thus, the crankcase
heater must be turned on a minimum of 12 hours before first time start, to prevent oil dilution and bearing stress on
initial start-up.
A 35-Watts crankcase heater is recommended for scroll compressor model and should be well attached to the
compressor shell.