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 effect 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 cool-ing coils. Close the strainer outlet valve and very carefully loosen the cap which is bolted to the strainer body. (Use all appropriate safety gear.) When all of the pressure is bled out of the strainer, remove the cap and lift out the strainer screen. Clean the strainer screen with a small brush, using an approved solvent. Reassemble the spring and screen in the strainer body. Replace the strainer cap loosely. Purge the air out of the strainer, by blowing refrigerant through it, then tighten the cap. After assembly is complete, test the unit for leaks.

CLEANING OIL FILTERS AND STRAINERS

Compressors arranged for forced feed lubrication are provided with lubricating oil strainers in the suction line of the lube oil pump and an oil filter installed in the pump discharge line. A gradual decrease in lubricating oil pressure indicates that the units need cleaning. Cleaning is accomplished in much the same manner as described for cleaning suction strainers.

When cleaning is necessary, the lubricating oil in the crankcase should be drained from the compressor and a new charge of oil, equal to the amount drained, should be added before re-starting the unit. When the compressor is put back into operation, the lube oil pressure must be adjusted to the proper setting by adjustment of the oil pressure regulator.

MAINTAINING COOLING COILS

Cooling coils should be inspected regularly and cleaned as required. The cooling coils should be defrosted as often as necessary to maintain the effectiveness of the cooling surface. Excessive build up 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 defrosting depends on such factors as refrigerant evaporating temperature, condition of door gaskets, moisture content of supplies placed in boxes, how frequently the doors are opened and atmospheric humidity. Cooling coils should be defrosted before the frost thickness reaches three-sixteenths of an inch. When defrosting, do not scrape or break off the frost, as this may cause damage to the coils.