• 20 parts
  • Checked September 2026

Parts of a Refrigerator Compressor

A sealed refrigerator compressor from outside, then cut away, then its two valves up close.

Parts of a Refrigerator Compressor

Name Date

Tap any part to read, rename or leave it out

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
More options

Write the name of each numbered part.Answer key

  1. Shell (housing)
  2. Suction tube
  3. Process tube
  4. Discharge tube
  5. Terminals
  6. Overload protector
  7. Starting relay
  8. Stator
  9. Rotor
  10. Crankshaft
  11. Connecting rod
  12. Piston
  13. Cylinder
  14. Suction muffler
  15. Discharge muffler
  16. Oil sump
  17. Valve plate
  18. Suction valve
  19. Discharge valve
  20. Cylinder head

Drawn for this site on 2026-09-30 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the parts of a freezer

All 20 parts on the diagram

Show the list

Shell and tubes 4

  1. Shell (housing) The motor and the pump are both inside it. It is welded shut and cannot be opened for repair, which is what hermetic means.
  2. Suction tube The gas is drawn into the shell through this tube. It passes round the motor and goes on to the cylinder.
  3. Process tube It is put in at the factory. It is an aid in drying and charging the system.
  4. Discharge tube The compressed gas leaves the compressor here. First it passes the discharge valve and the discharge muffler.

Motor and starting parts 5

  1. Terminals One is the common terminal. One goes to the start winding and one to the run winding.
  2. Overload protector When it has tripped, it has to cool before it closes again. Then it lets the motor run.
  3. Starting relay It disconnects the start winding. That happens as soon as the motor is near its running speed.
  4. Stator It has two windings: a start winding and a run (main) winding.
  5. Rotor It is fixed on the crankshaft. That way motor and pump share one shaft.

Pump 7

  1. Crankshaft It drives the piston. It also carries oil up from the bottom of the compressor to the bearing surfaces.
  2. Connecting rod It turns the crank pin's round-and-round into the piston's to-and-fro.
  3. Piston As it moves it pressures the gas. It pushes the gas out past the discharge valve.
  4. Cylinder Gas enters through the suction valve and leaves through the discharge valve.
  5. Suction muffler It quiets the pulses of the gas being sucked in.
  6. Discharge muffler It sits between the discharge valve and the discharge tube.
  7. Oil sump The crankshaft picks oil up from here. It carries the oil to the bearings.

Valves 4

  1. Valve plate It sits between the cylinder and the cylinder head. A port goes through it for each valve.
  2. Suction valve A reed valve that opens one way only. It opens when the piston draws back and shuts when the piston pushes.
  3. Discharge valve It opens when the piston pushes. It shuts again so the gas cannot come back.
  4. Cylinder head It has a room for the gas coming in. It has another for the gas going out.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it or describe the part: Wikipedia (Compressor, Reciprocating compressor, Reed valve; text only); a compressor maker's hermetic compressor service handbook (https://archive.org/details/Tecumseh-compressor1); a US Air Force refrigeration course text (https://archive.org/details/ERIC_ED183831); the US Navy manual Utilitiesman 3 and 2 (https://archive.org/details/ERIC_ED097442); and three US patents by three other compressor makers (US 4,547,131, US 5,205,723 and US 6,358,019, read on patents.google.com). No maker is named on the page. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; a schematic of no maker's product, nothing traced. Licence: own work

How it works

A refrigerator compressor is a small electric motor and a piston pump sealed together inside one welded steel shell. The drawing shows it from outside, then with the shell cut away, then the two valves enlarged.

Read the full guide

Follow the gas through it

Gas comes in through the suction tube, passes round the motor and goes through the suction muffler and the suction valve into the cylinder. The piston squeezes it and pushes it out past the discharge valve, through the discharge muffler and out of the discharge tube. Numbers 1 to 7 are outside: the shell, the three tubes, the terminals, the overload protector and the starting relay. Numbers 8 to 16 are inside the shell. Numbers 17 to 20 are at the end of the cylinder.

  • Three tubes, three widths: the suction tube is the widest, and the process tube is the short one pinched shut.
  • Makers lay the inside out differently: some put the pump on top of the motor, as here, and some below it.

Questions and answers

What is inside a refrigerator compressor?

An electric motor (stator and rotor) and a piston pump: a crankshaft, a connecting rod, a piston in a cylinder, and a valve plate with a suction valve and a discharge valve. They sit over a pool of oil, sealed inside the shell.

Why is a refrigerator compressor sealed?

So the refrigerant cannot leak out. With the motor inside the shell there is no turning shaft passing through the case, so no shaft seal to wear. The shell is welded shut and cannot be opened for repair; this is called a hermetic compressor.

What are the three tubes on a refrigerator compressor?

The suction tube, where the gas comes in; the discharge tube, where the compressed gas leaves; and the process tube, a stub put in at the factory as an aid in drying and charging the system.

What does the starting relay on a compressor do?

The motor has a start winding and a run winding. The starting relay is a switch that disconnects the start winding as soon as the motor is near its running speed.

More quizzes

Show 7 more

Browse Science Quizzes