South Carolina Air Conditioning Contractor Examination

According to the 2021 IMC, each length of pipe and tubing used in a mechanical system must:

• ABear the identification of the manufacturer
• BBe Type M copper regardless of the fluid
• CHave a pressure rating of at least 600 psig
• DBe painted the same color as the equipment it serves

When brazing ACR copper refrigerant tubing, dry nitrogen should be purged through the tube primarily to:

• APrevent internal copper-oxide scale that later circulates as debris
• BConvert remaining mineral oil into POE oil
• CPressure-test the finished joint at 600 psig
• DRaise the brazing temperature so the filler metal flows faster

Soft-drawn ACR copper tubing joined with a 45-degree flare fitting is generally limited to which field use?

• AFactory-charged line-set and equipment connections where the fitting is listed for the re…
• BConcealed joints inside a fire-rated shaft serving Group A2L refrigerant
• CAny joint on R-410A as a substitute for brazing
• DUnderground refrigerant piping without a protective sleeve

A 2021 IMC refrigerant pipe that penetrates two or more floor/ceiling assemblies generally must be:

• AInstalled in a fire-resistance-rated shaft, unless an IMC 1109 exception applies
• BWrapped with ordinary duct wrap in lieu of a shaft
• CLeft uninsulated so leaks are easy to see
• DRun in PVC conduit with solvent-welded joints

Under the South Carolina Air Conditioning contractor classification, which of the following is outside the licensed scope?

• AInstalling a rooftop DX air-conditioning unit that also provides electric heat
• BReplacing a split-system condensing unit and evaporator coil
• CInstalling a hot-water or steam boiler heating system
• DAltering the refrigerant piping on an environmental cooling system

Long, straight runs of refrigerant or chilled-water piping need expansion loops, offsets, or expansion joints primarily to:

• AAbsorb thermal expansion and contraction without overstressing joints and equipment conne…
• BProvide a built-in oil trap at every hanger
• CReplace the need for vibration isolators at the compressor
• DIncrease refrigerant velocity so oil returns faster

Service (king) valves on a split-system condensing unit are primarily used to:

• AIsolate the unit so the system can be pumped down, gauged, or recovered without cutting t…
• BRelieve high-side pressure automatically like a fusible plug
• CBlend POE oil into the liquid line
• DMeter refrigerant into the evaporator in place of a TXV

Under IMC 307, the condensate drain from a cooling coil must be not smaller than 3/4-inch internal diameter and must have a minimum horizontal slope of:

• A1/8 inch per foot (1-percent slope)
• B1/2 inch per foot
• CNo slope if the pipe is PVC
• D1/16 inch per foot

A thermostatic expansion valve (TXV) controls refrigerant flow by responding primarily to:

• AEvaporator superheat
• BCompressor amperage
• COutdoor dry-bulb temperature
• DCondenser subcooling only

A liquid-line filter-drier is installed to:

• ARemove moisture, acid, and particulate before the metering device
• BSeparate oil from discharge gas at the compressor
• CReplace the need for a vacuum after a burnout
• DRaise suction pressure by storing extra refrigerant

A chilled-water circulating pump that loses prime and sounds like gravel is most likely experiencing:

• ACavitation from insufficient net positive suction head
• BAn oversized impeller that is producing too little head
• CA closed balancing valve on the discharge only
• DA failed check valve that is stuck open on a single pump

A centrifugal pump delivers 80 gpm at 1,750 rpm. If the motor speed is reduced to 1,400 rpm and the system curve is unchanged, the new approximate flow is:

• A64 gpm
• B80 gpm
• C100 gpm
• D51 gpm

Insulation on a cold refrigerant suction line or chilled-water pipe must include a continuous vapor retarder primarily to:

• AKeep warm, moist room air from reaching the cold surface and condensing inside the insula…
• BAllow the pipe to sweat so leaks are easier to find
• CReplace the need for pipe hangers
• DIncrease the pipe's flame-spread rating above 200

Per IMC Table 305.4, the maximum horizontal hanger spacing for PVC pipe is:

• A4 feet
• B8 feet
• C12 feet
• D2 feet

Per IMC Table 305.4, copper or copper-alloy tubing must be supported horizontally at intervals not exceeding:

• A4 feet
• B6 feet
• C8 feet
• D12 feet

IMC 305.5 requires steel shield plates where nonferrous piping passes through holes or notches in framing and the pipe is less than 1-1/2 inches from the nearest edge. Those plates must be at least No. 16 gage and must extend not less than:

• A2 inches above sole plates and below top plates
• B6 inches above sole plates and below top plates
• CThe full height of the stud bay
• D1/2 inch above the sole plate and below the top plate

A cooling-coil drain pan is installed above a finished ceiling. If overflow from a clogged primary drain could damage the building, IMC 307 requires which of the following?

• AAn auxiliary drain pan with a separate drain, a secondary drain from the pan, or a listed…
• BA condensate pump without a safety switch
• CRouting the primary drain into a return-air plenum so leaks are noticed
• DA larger primary drain only; no secondary protection is required above ceilings

Per IMC Table 305.4, steel pipe may be supported horizontally at intervals not exceeding:

• A4 feet
• B8 feet
• C10 feet
• D12 feet

In the vapor-compression refrigeration cycle, the evaporator:

• AAbsorbs heat from the conditioned air and boils low-pressure liquid refrigerant
• BRaises refrigerant pressure without changing enthalpy
• CMeters liquid refrigerant by sensing condenser subcooling
• DRejects heat to outdoor air and condenses high-pressure vapor

Sensible cooling load is the portion of the load that:

• AChanges the dry-bulb temperature of the air
• BEquals latent load plus infiltration only
• CIs always 50 percent of the total load
• DChanges the moisture content of the air without changing dry-bulb temperature

Compared with a typical R-22 system, an R-410A comfort-cooling system operates at:

• ASignificantly higher pressures and uses POE oil
• BThe same pressures and the same mineral oil
• CA vacuum on the high side during normal cooling
• DMuch lower pressures and uses mineral oil

For the South Carolina Air Conditioning exam references, which ACCA manual is the procedure for commercial cooling and heating loads on small commercial buildings?

• AManual D, 3rd edition
• BManual J, 8th edition
• CManual N, 5th edition (2012)
• DManual S only

One refrigeration ton is defined as:

• A1,000 Btu/h
• B3,412 Btu/h
• C12,000 Btu/h
• D34,120 Btu/h

A room has a sensible cooling load of 8,640 Btu/h. Supply air is 55°F and the room is held at 75°F. Using Qs = 1.08 × CFM × ΔT, the required supply airflow is:

• A200 cfm
• B300 cfm
• C400 cfm
• D800 cfm

A small office has a total cooling load of 36,000 Btu/h. The designer uses 400 cfm per ton. What supply airflow should be used for equipment and duct sizing?

• A600 cfm
• B900 cfm
• C1,200 cfm
• D1,800 cfm

When performing a Manual J or Manual N cooling load, indoor design conditions are typically based on:

• AASHRAE/ACCA outdoor design dry-bulb and wet-bulb for the city plus the specified indoor d…
• BIndoor temperature only; outdoor conditions are ignored
• CAverage annual outdoor temperature
• DThe hottest outdoor temperature ever recorded at the site

A TXV-equipped R-410A unit has a liquid-line pressure that corresponds to 110°F saturated condensing temperature. The measured liquid-line temperature at the condensing-unit outlet is 98°F. Manufacturer target subcooling is 10°F. The system subcooling and most likely charge condition are:

• A12°F subcooling; correct if 10°F is the target
• B22°F subcooling; noncondensables in the condenser
• C8°F subcooling; slightly undercharged
• D12°F subcooling; slightly overcharged

A fixed-orifice R-410A system has a suction pressure corresponding to 40°F saturated evaporator temperature. The suction-line temperature at the evaporator outlet is 58°F. Manufacturer target superheat is 12°F. What is the superheat and the most likely charge condition?

• A18°F superheat; overcharged
• B98°F superheat; compressor floodback
• C12°F superheat; charge is correct
• D18°F superheat; undercharged or underfed

A typical split-system air conditioner places the compressor and condenser:

• AIn the return-air plenum
• BIn a refrigeration machinery room whenever the charge is under 3 pounds
• CIndoors with the evaporator and metering device outdoors
• DOutdoors, with the evaporator (and often the metering device) indoors

A hermetic scroll compressor on a comfort-cooling unit is most likely to be damaged by liquid floodback because:

• ALiquid refrigerant washes oil off the bearings and is incompressible in the scroll wraps
• BLiquid refrigerant increases oil viscosity so the motor overheats immediately
• CScrolls are designed to pump only liquid
• DFloodback raises superheat above 40°F

The most reliable field method to measure total airflow in a straight section of supply duct is:

• AReading only the furnace nameplate CFM
• BMeasuring return-grille area and assuming 2,000 fpm
• CA single-point velocity reading at the duct wall
• DA pitot-tube or hot-wire traverse in a straight run, averaged per a standard log-Tchebych…

A forward-curved blower delivers 2,000 cfm at 800 rpm. If speed is increased to 1,000 rpm and the system curve is unchanged, the new airflow is approximately:

• A1,600 cfm
• B2,000 cfm
• C2,500 cfm
• D3,125 cfm

Evaporator superheat is calculated by:

• AAdding suction pressure to liquid-line temperature
• BDividing compressor amps by outdoor dry-bulb
• CSubtracting liquid-line temperature from saturated condensing temperature
• DSubtracting saturated evaporator temperature from the suction-line temperature at the eva…

A Manual J cooling load uses 230 Btu/h sensible and 200 Btu/h latent per occupant. A conference room with 8 people contributes how much total internal occupant load?

• A1,840 Btu/h
• B1,600 Btu/h
• C3,440 Btu/h
• D8,000 Btu/h

A zone has a 12,000 Btu/h sensible load. The air handler supplies 55°F air to a 75°F room. Using Qs = 1.08 × CFM × ΔT, the designer should provide about:

• A278 cfm
• B400 cfm
• C556 cfm
• D1,200 cfm

During TAB of a constant-volume system, the preferred first step after verifying total blower airflow is to:

• AReplace the blower wheel
• BSet every diffuser to the same cfm regardless of the room load
• CClose all supply dampers and then open only the shortest run
• DProportionally balance the branches so each zone receives its design share of the actual…

On a conventional 24-volt heat-pump thermostat, the G terminal typically energizes the:

• AReversing valve only
• BCrankcase heater
• CCompressor contactor only
• DIndoor blower relay

A 24-volt cooling-only control circuit is wired R to Y through the thermostat, then Y through a high-pressure switch and low-pressure switch to the contactor coil, with the coil returning to C. If the high-pressure switch opens, the compressor will:

• ARun with the indoor blower locked out
• BReverse into heating
• CContinue to run because the thermostat is still calling
• DStop because the contactor coil circuit is interrupted

A dry-bulb economizer on a packaged rooftop unit is intended to:

• AReplace the need for a compressor high-pressure switch
• BHeat outdoor air with refrigerant hot gas year-round
• CAlways keep the outdoor damper fully closed during occupied hours
• DUse cool outdoor air to provide free cooling when outdoor conditions can meet the space l…

When IMC Chapter 11 requires a refrigeration machinery room because the refrigerant quantity exceeds the Table 1103.1 limits, the room must include a refrigerant detector that:

• AStarts the compressors to pump the charge outdoors
• BOpens all combustion appliances in the room to dilute the leak
• COnly logs the leak for the next annual inspection
• DActuates an alarm and mechanical ventilation at the specified concentration

A direct-expansion (DX) air-conditioning system cools the airstream by:

• ASpraying condenser water into the supply duct
• BUsing only an evaporative cooler with no refrigerant
• CCirculating chilled water through a coil that was cooled in a remote chiller
• DBoiling refrigerant inside the indoor coil so the air gives up heat directly to the refri…

In a pressure-independent VAV system, each VAV box typically maintains its airflow setpoint by:

• AClosing the return damper in that room
• BChanging the refrigerant metering device at each diffuser
• CCycling the rooftop compressor on a 24-volt space thermostat only
• DModulating the box damper using a flow sensor so actual cfm matches the thermostat demand

Which indoor component is required on a cooling split system but is not, by itself, a heat source?

• AThe evaporator coil and condensate drain pan
• BThe gas burner assembly
• CThe steam boiler
• DThe Type B vent connector

The reversing valve on an air-source heat pump is used to:

• AChange the direction of refrigerant flow so the indoor coil can be either evaporator or c…
• BReverse the indoor blower rotation
• CSwap the TXV sensing bulb from suction to liquid line
• DConvert natural gas to LP gas

During a typical air-source heat-pump defrost cycle:

• AOnly the crankcase heater runs
• BThe reversing valve is mechanically locked in heating for 24 hours
• CThe outdoor fan stays on high and the indoor coil is de-energized
• DThe unit reverses to cooling, the outdoor fan stops, and auxiliary heat often comes on to…