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Class 4 (4th Engineer) MEP 📅 Oct 2025

Exam Question

(a) What are the reasons for foaming in refrigeration compressor crankcase? (4)

(b) Describe the causes for the following in the domestic refrigeration system: (12)

(i) Frequent cut-in and cut-out of the compressor.

(ii) Low oil pressure cut-out of the compressor.

(iii) High pressure cut-out of the compressor.

(iv) Frosting in the compressor suction side.

Reference Answer

### (a) Reasons for Foaming in Refrigeration Compressor Crankcase
Foaming in a refrigeration compressor crankcase is the violent and rapid boiling of refrigerant that has dissolved into the lubricating oil. This phenomenon primarily occurs during compressor startup.
**Mechanism and Causes:**
1. **Refrigerant Migration and Absorption:**

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