Continuous liquid flood back can occur with a wrong dimensioning, a wrong setting or malfunction of the
expansion device or in case of evaporator fan failure or blocked air filters. A suction accumulator providing
additional protection as explained hereunder can be used to solve light continuous liquid flood back.
Suction accumulator
A suction accumulator offers protection against refrigerant flood back at start-up, during operations or defrosting
by trapping the liquid refrigerant upstream from the compressor. The suction accumulator also protects against off -
cycle migration by providing additional internal free volume to the low side of the system.
A suction accumulator must be carefully dimensioned, taking into account the refrigerant charge as well as the gas
velocity in the suction line. The accumulator should not be sized for less than 50 % of the total system charge. Tests
must be conducted to determine the actual refrigerant holding capacity needed for the application.
Depending on the operating conditions it may happen that the recommended connections of the accumulator are
one size smaller than the suction line.
Power supply and electrical protection
Wiring information Requirements
The wiring diagrams below are examples for a safe and reliable compressor wiring. In case an alternative wiring
logic is chosen, it is imperative to respect the following rules:
When a safety switch trips, the compressor must stop immediately and must not re-start until the tripping condition
is back to normal and the safety switch is closed again. This applies to the LP safety switch, the HP safety switch, the
discharge gas thermostat and the motor safety thermostat.
In specific situations, such as winter start operation, an eventual LP control for pump-down cycles may be
temporarily bypassed to allow the system to build pressure. But it remains mandatory for compressor protection to
apply an LP safety switch. The LP safety switch must never be bypassed.
Pressure settings for the LP and HP safety switch and pump-down listed in table from section “Low pressure”.
When ever possible (ie. PLC control), it is recommended to limit the possibilities of compressor auto restart to less
than 3 to 5 times during a period of 12 hours when caused by motor protection or LP safety switch tripping. This
control must be managed as a manual reset device.
Scroll compressors, CH290 and CH485 | Application
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