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Vapor- compression refrigeration loop

 Vapor- compression refrigeration loop what each part does

Flow path (colors match the sketch)

High side:

Compressor→condenser→receiver→   filter-drier sight glass (liquid & moisture indicator) →solenoid valve→ expansion valve.

Low side:

Evaporator→suction accumulator→suction filter ball valve→ low-pressure switch →compressor.

Motors drive the condenser fan and the evaporator blower.



Component roles (in order of flow)


1 Compressor: Pulls low-pressure vapor from the evaporator and compresses it to high-pressure, high-temperature vapor. Sets the cycle.

2 Oil separator: Strips oil from discharge gas and returns it to the crankcase. Cuts oil carry-over.

3 Condenser + fan motor: Rejects heat to ambient. Vapor condenses to liquid and subcools.

4 Receiver: Stores and stabilizes the liquid charge. Ensures solid liquid feed to the line.

5 Filter-drier: Removes moisture, acids, and debris. Protects the TXV and compressor.

6 Sight glass / moisture indicator: Bubble check for flashing and color disk for dryness. Green/dry = OK; bubbles/yellow = investigate subcooling or dehydration.

7 Solenoid valve: Closes on stop or alarm to prevent off-cycle migration. Enables pump-down control with the LP switch.

8 Expansion valve (TXV/EEV): Drops pressure and meters refrigerant based on superheat at the evaporator outlet. Creates the liquid/vapor mix.

9 Evaporator + blower motor: Boils refrigerant by absorbing room/air heat. Outlet is superheated vapor.

10 Suction accumulator: Traps any liquid returning from the coil. Prevents slugging.

11 Suction filter (core): Catches fines, especially after burnouts. Remove or bypass after cleanup.

12 Ball valve: Service isolation for recovery and diagnostics.

13 Low-pressure switch: Safety and control. Cuts out on loss of charge or after pump-down; cuts in on restart.


How pump-down works (typical)

  • Thermostat shuts solenoid closes.
  • Compressor keeps running, sucking low side down to LP cut-out.
  • System stops with most refrigerant parked as liquid upstream of the TXV. Prevents migration, eases restarts.
Field checks that prove the system

  • Subcooling at liquid line leaving condenser/receiver (solid column to TXV).
  • Superheat at evaporator outlet (TXV set correctly; accumulator stays cool only at bottom).
  • Sight glass clear and dry; no bubbles at steady load.
  • Oil return stable; separator warm on discharge, cool return.
  • Controls: solenoid closes, LP switch cuts out; safeties labeled and accessible.

Bottom line

Orange = reject heat and manage liquid.

Blue = absorb heat and protect the compressor. The accessories shown-oil separator, receiver, filter-drier, sight glass, solenoid, accumulator, suction filter, LP switch-exist to keep the core cycle efficient, dry, and safe.

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