Installation & Maintenance Practices Flashcards
7 cards from real CRST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Installation & Maintenance Practices flashcards as text
When installing a condensing unit outdoors, what minimum clearance is typically required on the air discharge side?
Answer: 24 inches
Most manufacturers require at least 24 inches of clearance on the discharge side to prevent recirculation of hot condenser air.
Which refrigerant line on a split system should be insulated to prevent condensation and heat gain?
Answer: Suction line only
The suction line carries low-pressure, low-temperature refrigerant vapor and must be insulated to prevent heat gain and condensation.
What is the purpose of a crankcase heater on a refrigeration compressor?
Answer: Prevent refrigerant migration into compressor oil during off cycles
Crankcase heaters keep the oil warm to prevent refrigerant from migrating and diluting the compressor lubricant during the off cycle.
A technician is installing copper refrigerant tubing and needs to make a brazed joint. What gas should be used to purge the line during brazing?
Answer: Dry nitrogen
Dry nitrogen purging during brazing prevents internal oxidation scale that can clog metering devices and damage compressor valves.
After installing a new refrigeration system, what is the recommended procedure before charging with refrigerant?
Answer: Pressure test with nitrogen, then evacuate to 500 microns or below
The system should be pressure tested with dry nitrogen to check for leaks, then evacuated to 500 microns or lower to remove air and moisture before charging.
Which type of filter-drier core is recommended for systems using POE (polyolester) oil?
Answer: Molecular sieve core
Molecular sieve desiccant cores are preferred with POE oil systems because they do not react adversely with the highly hygroscopic ester oil.
When mounting a remote condenser on a rooftop, which installation requirement is most critical for proper oil return?
Answer: Pitch refrigerant lines toward the compressor and install traps on long vertical risers
Proper pitch and oil traps on vertical suction risers ensure oil entrained in refrigerant vapor is carried back to the compressor.