313D System Installation and Startup 2

Question 1

When installing a split-system condenser outdoors, what is the minimum recommended clearance from the top of the unit to any overhead obstruction?

Accepted Answer

48 inches

Answer

Most manufacturers require at least 48 inches of clearance above the condenser to allow unrestricted discharge airflow and prevent hot air recirculation.

Question 2

During system startup, the technician measures suction pressure lower than expected and superheat higher than normal. What is the most likely cause?

Accepted Answer

Restricted liquid line filter-drier

Answer

A restricted liquid line filter-drier causes a pressure drop that starves the metering device, resulting in low suction pressure and high superheat.

Question 3

What is the purpose of installing a crankcase heater on a scroll compressor before startup?

Accepted Answer

To boil off refrigerant that has migrated into the oil

Answer

Crankcase heaters vaporize liquid refrigerant that has migrated into the compressor oil sump, preventing slugging damage on startup.

Question 4

When connecting refrigerant line sets, which brazing rod alloy is preferred to minimize oxidation scaling inside copper tubing?

Accepted Answer

Stay-Silv 15 with nitrogen purge

Answer

Stay-Silv 15 (15% silver) used with a nitrogen purge prevents oxidation scale formation inside the tubing that could contaminate the system.

Question 5

A residential condensing unit is installed on a rooftop. Which installation precaution is most important for preventing vibration transmission to the structure?

Accepted Answer

Using rubber isolation pads or spring isolators under the unit

Answer

Rubber isolation pads or spring isolators absorb compressor vibration and prevent it from transmitting through the structure and causing noise complaints.

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

313D System Installation and Startup 2