Which of the following is another effect of small carbon particles inside the refrigeration system?

• A. Grounding hermetic compressor terminals
• B. Restricting metering devices
• C. Increased efficiency
• D. Noise reduction

Answer: (B)

Small carbon particles in a refrigeration system travel with the refrigerant and tend to lodge in narrow flow passages. Metering devices, like capillary tubes and expansion valves, have very small openings to regulate the refrigerant entering the evaporator. When carbon particles get into these passages, they can get stuck and reduce or block the flow, effectively restricting the metering device.

This restriction disrupts proper metering, leading to reduced refrigerant flow to the evaporator, lower cooling capacity, possible higher superheat, and increased compressor load or wear. That’s why restricting the metering device is the best answer.

Other options don’t fit as well: grounding compressor terminals is an electrical fault unrelated to carbon particles; increased efficiency would not occur from particle presence; and while particles can cause abnormal operation, they do not typically result in noise reduction.