Two spiral elements form the compression chamber.

One is fixed and the other orbits.

Pockets of refrigerant are trapped and driven inward.

The volume reduces continuously as they travel.

There are very few moving parts.

By switching whole compressors in and out.

Several compressors sit in one machine.

As many run as the moment requires.

Capacity arrives in steps rather than continuously.

Control is simple and robust.

Less than it might appear.

A scroll compressor is efficient whenever it runs.

Three of four running is near its best.

Nothing is being throttled back.

The steps are the only real compromise.

A failure affects one circuit, not the machine.

The remaining circuits keep running.

Output is reduced rather than lost.

Cooling continues while a part is sourced.

That property comes from the arrangement itself.

The smaller and middle capacities.

Offices, retail and smaller institutional buildings.

Modular blocks combine for larger duties.

Above that range other compressors take over.

The overlap with screw machines is real.

When the load needs fine continuous modulation.

Stepped capacity suits many buildings but not all.

Tight process control is better served elsewhere.

Very large duties belong to centrifugal machines.

Conditions matter as well as tonnage.

Comparatively little, by design.

Few moving parts means fewer wear points.

Compressors are usually replaced rather than overhauled.

Coil cleanliness and refrigerant charge remain routine.

Electrical and control checks complete the picture.