With reference to refrigeration plant; (a) state THREE indications of a loss in refrigerant charge; (b) state THREE methods of detecting the location of the source of leakage; (c) describe a safe method of bringing the gas charge back to its normal working level.
(a) Indications of a loss in refrigerant charge (3 marks)
Low suction pressure and possible compressor overheating.
Reduced cooling capacity – refrigerated spaces not reaching set temperatures.
Bubbles in the liquid line sight glass (indicating vapour instead of full liquid).
(b) Methods of detecting the location of a refrigerant leak (3 marks)
Electronic leak detector (sniffer) – senses refrigerant gas around joints and fittings.
Soap solution test – bubbles form at joints where gas is escaping.
Oil stains or frosting around leaking fittings, since refrigerant often carries lubricating oil with it.
(c) Safe method of restoring gas charge (4 marks)
Connect a refrigerant cylinder to the system using proper charging hoses and manifold gauge.
If charging vapour, connect to the suction side of the compressor while it is running, introducing refrigerant slowly.
If charging liquid, connect at the liquid line downstream of the condenser/receiver, ensuring the compressor is stopped to prevent liquid slugging.
Monitor pressures, sight glass, and temperatures carefully to ensure the system is correctly charged, without overfilling.
