Where a liquid line strainer is installed, it should be cleaned at the same intervals as the suction strainer. If a liquid line strainer becomes clogged to the extent that it needs cleaning, a loss of refrigeration will take place. The tubing on the outlet side of the strainer will be much colder than the tubing on the inlet side.

To clean the liquid line strainer, secure the receiver outlet valve and wait a few minutes to allow any liquid in the strainer to flow to the cooling coils. Then close the strainer outlet valve and very carefully loosen the cap that is bolted to the strainer body. (Use goggles to protect your eyes!) When all the pressure is bled out of the strainer, remove the cap and lift out the strainer screen. Clean the strainer screen with an approved solvent and a small brush. Reinstall the spring and screen in the strainer body; then replace the strainer cap loosely. Purge the air out of the strainer by blowing refrigerant through it; then tighten the cap. After the assembly is complete, test the unit for leaks.

CLEANING OIL FILTERS AND STRAINERS

Compressors arranged for forced-feed lubrication have lubricating oil strainers in the suction line of the lube-oil pump. An oil filter may be installed in the pump discharge line. A gradual decrease in lubricating oil pressure indicates that these units need cleaning. This cleaning is done in much the same manner as described for cleaning suction strainers.

When cleaning is necessary, drain the lubricating oil in the crankcase from the compressor. Add a new charge of oil, equal to the amount drained, before restarting the unit. When the compressor is put back into operation, adjust the lube-oil pressure to the proper setting by adjusting the oil pressure regulator.

MAINTAINING COOLING COILS

You should inspect the cooling coils regularly and clean them as required. Defrost the cooling coils as often as necessary to maintain the effectiveness of the cooling surface. Excessive buildup of frost on the cooling coils will result in reduced capacity of the plant, low compressor suction pressure, and a tendency for the compressor to short-cycle. The maximum time interval between defrostings depends on such factors as condition of door gaskets, moisture content of supplies placed in boxes, frequency of opening doors, atmospheric humidity, and refrigerant evaporating temperatures.

You should always defrost the cooling coils before the frost thickness reaches three-sixteenths of an inch. When defrosting the coils, be sure that you do NOT try to scrape or break the frost off. Improper defrosting will cause serious damage to the coils.