Compressor selection, replacement and service

A reliable selection connects the required duty to an exact model and verified operating conditions. Replacement also requires the installed system’s identity and the reason for the previous failure.

Guide

Contents

Prepare selection data

Record the equipment and compressor nameplates, model revisions, refrigerant, oil, cooling or heating duty, operating range, electrical supply and control. Add suction and discharge conditions, superheat or inlet temperature, rating liquid conditions and speed. For replacement, include connection sizes, orientation, mounting and drive/controller identity. Mark missing values as unknown.

Confirm an exact model

Check the documented refrigerant and oil compatibility, performance table, complete operating envelope, electrical limits and protection requirements. Match the equipment maker’s replacement requirements. Record the source document and revision for the technical decision; a generic cross-reference or similar shell is not enough.

Diagnose before replacing

Record alarms and operating measurements. Check supply, commands and protective trips before concluding a mechanical failure. Evaluate heat exchangers, refrigerant feeding, liquid return, motor temperature and lubrication. A root cause left in the circuit can damage the replacement. Competent personnel perform refrigerant and electrical work under the exact equipment procedure.

Model-specific documents

A request checklist can name a specification, performance selection, wiring diagram, installation and service instructions, applicable conformity documents and warranty terms. Naming these document types is not evidence that they have been issued or received. Check the manufacturer, full model code, document revision, stated scope and supplied configuration on the actual files.

Technical selection, quotation and acceptance

The technical selection states a model and duty. The quotation identifies quantity, condition, included drive and accessories, documents, warranty, lead time and commercial terms. Commissioning then records the installed identity, settings, measured operation and protection checks. A quotation does not prove commissioning, and a reference page does not confirm a supply offer.

Prepare a compressor request

Pressure conversion and pressure-ratio calculation · model selection unavailable

The pressure tool converts the supplied values and calculates the absolute discharge-to-suction pressure ratio. The request form records other requirements. Neither function selects a compressor, calculates capacity or confirms a refrigerant cycle, diagnosis or interchangeability.

For a technical review, identify the exact model and refrigerant, duty and rating conditions, electrical supply and control, oil, dimensions/connections, and the reason for replacement or service. Missing information remains unknown.

Selection / replacement · Service

Absolute pressures and pressure ratio

Use suction and discharge pressures for the same stated operating condition and compatible measurement definitions. This is a pressure calculation; it does not check whether a compressor can operate at those pressures.

Method: 1 bar = 100 kPa; 1 MPa = 1000 kPa. Convert each input to kPa. For gauge pressure, p(abs) = p(gauge) + p(atm). For absolute pressure, use the entered value directly. r = p(discharge, abs) / p(suction, abs); r has no unit.

Both absolute pressures must be positive. Enter a positive absolute atmospheric pressure whenever either input is gauge. A negative gauge reading is allowed if its absolute pressure remains positive. Atmosphere is never assumed.

Example: suction 2 bar absolute and discharge 8 bar absolute give 200 kPa, 800 kPa and r = 4. The same result follows from 1 bar gauge and 7 bar gauge with an explicitly supplied atmosphere of 1 bar absolute.

The calculation does not provide cooling capacity, power, discharge temperature, an operating envelope, refrigerant/oil compatibility, diagnosis or a replacement model. Pressure sources, measurement uncertainty, operating stability and model limits remain unverified. Displayed results are rounded; extreme values outside finite numeric precision are rejected.