Refrigeration practice (ammonia system): During refrigerant charging in an ammonia vapour compression plant, should the charging connection be made at the compressor outlet (discharge) line?

Introduction / Context:
Safe and effective charging of ammonia systems requires connecting at the correct side of the cycle. The question probes whether charging at the compressor discharge is appropriate.

Given Data / Assumptions:

• Ammonia (R-717) vapour compression system.
• Normal charging operation (no emergency).
• Compressor with suction (low-pressure) and discharge (high-pressure) lines.

Concept / Approach:
Charging is typically done on the low-pressure side (suction line or receiver/liquid line with proper throttling and precautions) to avoid forcing refrigerant into the high-pressure discharge where pressures and temperatures are high. Introducing refrigerant at the discharge risks pushing liquid toward the compressor or over-pressurizing components.

Step-by-Step Solution:
Identify low side: evaporator outlet to compressor suction.Connect charging cylinder via manifold to the low side so the system draws refrigerant safely.Avoid discharge side connection to prevent charging against high pressure and potential liquid slugging.

Verification / Alternative check:
Field procedures and manufacturer service manuals specify suction-side charging for vapour charging; liquid charging uses receiver/liquid line with metering and system off as applicable, still not at compressor discharge.

Why Other Options Are Wrong:

• Agree/Only for liquid charging/Only in vacuum/Only for small systems: discharge-line charging is not standard good practice due to high temperature/pressure and compressor safety concerns.

Common Pitfalls:
Feeding liquid directly into the suction without flashing can damage compressors. Use correct procedures (vapour at suction, or controlled liquid into receiver/liquid line) with proper throttling and monitoring.

Final Answer:
Disagree