CSLB General Building (B) — All Questions

In the basic refrigeration cycle, which component absorbs heat from the conditioned space?

• a.The condenser
• b.The evaporator✓
• c.The compressor
• d.The metering device

The evaporator is where low-pressure liquid refrigerant boils and absorbs heat from the indoor air, cooling the space. The condenser then rejects that heat outdoors. This heat-absorption step is the cooling effect of the system.

What is the primary function of the compressor in the refrigeration cycle?

• a.To absorb heat from the space
• b.To meter refrigerant into the evaporator
• c.To raise the pressure and temperature of the refrigerant vapor and circulate it✓
• d.To drain condensate

The compressor draws in low-pressure vapor from the evaporator and compresses it to a high pressure and temperature, then discharges it to the condenser. This pressure difference drives refrigerant flow around the loop. It is often called the heart of the system.

The condenser in an air-conditioning system performs which function?

• a.Absorbs heat and boils refrigerant
• b.Rejects heat and condenses refrigerant vapor into liquid✓
• c.Meters refrigerant flow
• d.Filters the air

In the condenser, high-pressure, high-temperature vapor gives up heat to the outdoor air and condenses into a high-pressure liquid. This heat rejection is what allows the cycle to remove heat from indoors. Airflow across the condenser coil is essential for this process.

A thermostatic expansion valve (TXV) controls refrigerant flow into the evaporator to maintain what?

• a.Constant condenser pressure
• b.Constant compressor speed
• c.A relatively constant evaporator superheat✓
• d.Constant subcooling

A TXV modulates refrigerant flow to hold a stable superheat at the evaporator outlet, matching flow to the load. This keeps the coil fed efficiently and protects the compressor from liquid floodback. It responds to the temperature and pressure of the suction line.

Superheat is defined as the temperature of the refrigerant vapor above what?

• a.Its condensing temperature
• b.Its saturation (boiling) temperature at the existing pressure✓
• c.The outdoor ambient temperature
• d.The compressor discharge temperature

Superheat is the number of degrees the refrigerant vapor has been heated above its saturation temperature for the measured pressure. Adequate superheat ensures only vapor, not liquid, returns to the compressor. Technicians measure it to evaluate evaporator charge and load.

A technician measures a suction pressure whose saturation temperature is 40 F and a suction line temperature of 52 F. What is the superheat?

• a.4 degrees
• b.8 degrees
• c.12 degrees✓
• d.20 degrees

Superheat equals the suction line temperature minus the saturation temperature: 52 F minus 40 F equals 12 degrees. This value helps confirm proper evaporator feeding and charge. Very low superheat risks liquid floodback, while very high superheat suggests underfeeding.

Subcooling is measured at which point in the system?

• a.At the evaporator outlet
• b.At the condenser outlet (liquid line)✓
• c.At the compressor suction
• d.At the filter on the return duct

Subcooling is measured at the condenser outlet by comparing the liquid line temperature to the saturation temperature for the high-side pressure. It indicates how much the liquid has cooled below its condensing point. Subcooling is a primary charging check on TXV systems.

On a system with a condensing saturation temperature of 105 F and a liquid line temperature of 95 F, what is the subcooling?

• a.5 degrees
• b.8 degrees
• c.10 degrees✓
• d.15 degrees

Subcooling equals the saturation temperature minus the liquid line temperature: 105 F minus 95 F equals 10 degrees. This is a typical target range for many TXV systems. Low subcooling can indicate an undercharge, while high subcooling can indicate an overcharge or restriction.

On a fixed-orifice (piston) system, which method is generally used to check the charge?

• a.Subcooling only
• b.The superheat method using target superheat charts✓
• c.Weighing the compressor
• d.Measuring duct static pressure

Fixed-orifice metering devices are charged by the superheat method, comparing measured superheat to a target based on indoor wet-bulb and outdoor dry-bulb temperatures. TXV systems, by contrast, are typically charged by subcooling. Using the correct method for the metering device is essential.

Under EPA Section 608, what must a technician do with refrigerant before opening most systems for service?

• a.Vent it to the atmosphere
• b.Mix it with nitrogen
• c.Recover it using certified recovery equipment✓
• d.Burn it off

Section 608 prohibits knowingly venting most refrigerants and requires recovery into approved equipment before opening a system. This protects the atmosphere and conserves refrigerant. Only certified technicians using certified equipment may perform this work.EPA Section 608

EPA Section 608 certification is required for technicians who do what?

• a.Only install ductwork
• b.Maintain, service, repair, or dispose of equipment that could release regulated refrigerants✓
• c.Only wire thermostats
• d.Only design duct systems

Section 608 requires certification for anyone who could release ozone-depleting or certain other regulated refrigerants during service, maintenance, repair, or disposal. Different certification types cover small appliances, high-pressure, and low-pressure systems. Working with refrigerant without certification is a violation.EPA Section 608

Evacuating a system with a vacuum pump primarily removes what?

• a.Refrigerant oil
• b.Copper scale
• c.Moisture and non-condensable gases such as air✓
• d.The compressor windings

A deep vacuum boils off moisture and pulls out air and other non-condensables that would otherwise raise head pressure, form acids, or cause icing at the metering device. A micron gauge verifies the target vacuum is reached and held. Proper evacuation is essential before charging.

A micron gauge is used during evacuation to measure what?

• a.Refrigerant weight
• b.The depth of vacuum in the system✓
• c.Superheat
• d.Airflow

A micron gauge measures the absolute pressure (depth of vacuum) far more precisely than a compound gauge, confirming that the system is dry and tight. Technicians pull the system down to a target micron level and perform a decay test. Failure to hold vacuum indicates moisture or a leak.

Which instrument or method is commonly used for pinpointing small refrigerant leaks?

• a.A megohmmeter
• b.A manometer
• c.An electronic leak detector or bubble solution✓
• d.A pyrometer

Electronic leak detectors sense refrigerant escaping at joints, and bubble solutions reveal leaks visibly. Ultraviolet dye is another method for hard-to-find leaks. Locating and repairing leaks is required before recharging a system.

As a general principle, adding refrigerant charge to a properly running system tends to do what to the low-side pressure?

• a.Lower it significantly
• b.Raise it✓
• c.Have no effect
• d.Reverse compressor rotation

Adding charge generally raises system pressures, including the suction (low-side) pressure, while removing charge lowers them. Technicians interpret these trends together with superheat and subcooling. Charging must be verified against manufacturer targets, not pressure alone.

A refrigerant metering device such as a fixed orifice or TXV creates what effect on the refrigerant?

• a.Raises its pressure
• b.Condenses it to liquid
• c.Causes a pressure drop so it can boil at a low temperature in the evaporator✓
• d.Superheats the vapor before the condenser

The metering device restricts flow, dropping the high-pressure liquid to a low pressure so it can boil at a low temperature and absorb heat in the evaporator. This division between high and low sides is central to the cycle. TXVs also modulate this flow to control superheat.

Which category of refrigerants is being phased down under regulations due to high global warming potential?

• a.Water-based refrigerants
• b.Many high-GWP HFC refrigerants✓
• c.Nitrogen
• d.Carbon dioxide only

Regulations at the federal and California level are phasing down high global-warming-potential HFC refrigerants in favor of lower-GWP alternatives. Technicians must stay current on approved refrigerants and handling rules. Recovery and reclamation remain required under Section 608.EPA Section 608

A compressor that is trying to compress liquid refrigerant returning from the evaporator can suffer what damage?

• a.Improved efficiency
• b.Higher superheat
• c.Slugging and mechanical damage to valves or bearings✓
• d.Lower amp draw

Liquid refrigerant is nearly incompressible, so liquid floodback or slugging can damage compressor valves, bearings, and rods. Maintaining adequate superheat prevents liquid from reaching the compressor. This is why superheat is carefully controlled.

When comparing the two sides of an operating system, the discharge line is normally which relative to the suction line?

• a.Colder and lower pressure
• b.Hotter and higher pressure✓
• c.The same temperature and pressure
• d.Filled only with liquid

The discharge line leaving the compressor carries high-pressure, high-temperature vapor, while the suction line carries low-pressure, cooler vapor returning to the compressor. Recognizing these normal conditions helps a technician diagnose faults. Abnormal readings point to charge or airflow problems.

A reciprocating compressor changes the refrigerant state by doing what?

• a.Condensing vapor to liquid
• b.Metering liquid flow
• c.Using pistons to compress low-pressure vapor into high-pressure vapor✓
• d.Boiling the refrigerant

A reciprocating compressor uses pistons driven by a crankshaft to draw in and compress refrigerant vapor, raising its pressure and temperature. Scroll and rotary compressors accomplish the same result by different mechanisms. The compressor circulates refrigerant and establishes the high and low sides.

High condenser (head) pressure with normal charge is most often caused by what?

• a.Overcharged suction line insulation
• b.Poor airflow or a dirty condenser coil✓
• c.A shorted thermostat
• d.An oversized return grille

Restricted condenser airflow, from a dirty coil, failing fan, or blocked clearance, prevents adequate heat rejection and raises head pressure. Non-condensables or overcharge can also raise head pressure. Cleaning the coil and confirming fan operation are first steps.

The saturation temperature corresponding to a measured pressure is found using what?

• a.The unit nameplate
• b.A duct calculator
• c.A pressure-temperature (PT) chart or app for the specific refrigerant✓
• d.The electrical schematic

A pressure-temperature chart lists the saturation temperature for each pressure of a given refrigerant. Technicians use it to calculate superheat and subcooling from gauge readings. Each refrigerant has its own PT relationship, so the correct chart must be used.