North Carolina HVAC Exam Prep FREE Sample Exam

Why must a refrigerant distributor create a deliberate pressure drop at its nozzle?

So the liquid refrigerant is completely flashed to vapor before it enters the circuits, because evaporator circuits are designed to be fed with dry vapor only

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So the expansion valve can be eliminated from the system, because the distributor nozzle alone is intended to meter the entire refrigerant flow to the coil

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So the pressure in the evaporator is raised above suction pressure, because a distributor works by pressurizing the coil rather than by dividing the flow

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So the two-phase mixture distributes evenly to every circuit despite small differences in circuit pressure drop

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A homeowner asks why the new R-454B air handler runs its blower for a while after a leak sensor trips, even though cooling has stopped. What is the correct explanation?

The blower is removing residual heat from the electric heat strips, a normal cool-down sequence that happens to coincide with the sensor alarm event

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The blower pressurizes the duct system so refrigerant vapor is forced back through the leak point into the coil, resealing the system temporarily

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The blower dilutes and disperses leaked refrigerant through the duct system so room concentration stays low

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The blower run is a fault in itself, because mitigation design requires the air handler to shut down every moving part the instant a sensor trips

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On a fixed-orifice system being checked with a manufacturer’s target-superheat chart, a technician records the outdoor dry-bulb temperature. What second temperature does the chart require as its other input?

Liquid-line temperature at the condenser outlet

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Indoor wet-bulb temperature, which reflects the total indoor heat and moisture load

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Suction-line temperature at the compressor inlet

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Return-air dry-bulb temperature only, with no moisture measurement, measured at the return-air grille

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In a zone-valve hydronic system, how is heat delivered to only the zone that is calling?

One circulator per zone runs while all zone valves stay open, and each zone is heated in turn by timers in the boiler control rather than by its own thermostat

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A single boiler pump reverses direction for each zone

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Each zone has a motorized valve opened by its own thermostat, while a shared circulator moves water through whichever valves are open

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Each zone has its own boiler controlled by one thermostat

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A homeowner calls because the outdoor unit is steaming, the outdoor fan has stopped, and a whoosh was heard, while the unit is heating on a frosty morning. What should the technician explain first?

The compressor has failed and the unit should be shut off at the breaker immediately

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The refrigerant charge is escaping as steam and the area should be evacuated

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This is a normal defrost: the reversing valve shifted, the fan stopped, frost is melting into visible vapor, and the cycle will end and heating will resume in a few minutes

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The unit has mistakenly switched to cooling for the rest of the day

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An electronic bypass arrangement uses a plenum static pressure sensor wired to the control. What does the control do with that signal?

It uses the signal only to log pressure for a service report, because electronic bypass dampers are positioned by zone thermostat count and never by measured duct pressure

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It converts the pressure signal into a call for second-stage heat, because high plenum pressure is the panel's standard indication that more capacity is needed in the zones

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It modulates the bypass damper to hold the set static pressure

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It shuts the bypass damper tighter as pressure rises, because relieving a zoned system requires forcing all blower airflow through whichever zones remain open

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On a ladder diagram, a thermostat contact, a limit switch, and a relay coil appear in series on one rung, and the relay contacts are on another rung. If the limit opens, what happens?

Only the thermostat is bypassed and the relay stays energized

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The relay coil de-energizes and its contacts return to their shelf state

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The relay contacts weld closed to maintain operation

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Power flows backward through the coil to the transformer

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Windows condense heavily on cold winter mornings in a tight new home with a large family, showers, and cooking. Indoor humidity reads 48%. What is the most likely diagnosis?

The humidifier is undersized, so raising indoor humidity further will warm the window glass and stop the condensation from forming

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The windows are leaking refrigerant, because condensation on glass is a recognized sign of a cooling-system charge problem in winter

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The furnace is oversized for cooling, which explains winter window moisture even though the cooling system is not operating at all

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Indoor moisture generation exceeds removal, so humidity must be lowered and ventilation or exhaust increased rather than adding humidification.

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Supply ducts run through an unconditioned ventilated attic in a hot climate. Why is duct insulation with a sealed vapor retarder required there?

It makes the duct airtight, so joints in attic ducts never need to be sealed with mastic or approved tape at installation

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It limits heat gain into the cold airstream and keeps the duct surface from sweating.

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It raises supply-air temperature in summer so registers feel warmer and occupants stop reporting cold drafts in the morning

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It replaces structural duct support, allowing long attic runs to rest directly on ceiling joists without hangers or straps

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Why does the furnace or air handler blower matter to a cooling system’s rated combination?

The blower matters only for heating season, because cooling capacity is set entirely at the outdoor unit and airflow is secondary

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Blower airflow across the coil is part of the tested combination, and wrong airflow changes capacity, efficiency, and dehumidification

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A stronger blower always raises the rating, so oversizing the air handler is a reliable way to gain extra efficiency points

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Blower selection affects only noise level, since the coil removes the same moisture regardless of the air volume crossing it

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A licensee claiming the 10-year route had a disciplinary order imposing suspension during year six of the claimed period. Does the period still qualify as good standing?

Yes, because good standing requires only that all annual license fees are current at application, as applied to the particular circumstances described in this question.

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Yes, because a suspension order affects the license status only during the suspension itself.

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No, because good standing excludes a disciplinary order imposing suspension during the 10-year period.

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No, but only if the suspension lasted longer than one full year of the claimed ten-year period.

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An installer proposes running plastic gas pipe above ground along a North Carolina building wall and then indoors to a furnace, arguing plastic is approved gas piping without location limits. Which correction is right?

Plastic pipe may be used indoors if it is painted, because paint supplies the protection the location rules are seeking

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Plastic fuel-gas piping is permitted only underground outdoors, must be installed with an electrically conductive tracer wire, and must transition to above-ground or indoor piping only through approved risers and fittings

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Plastic pipe may be used anywhere steel is used, because the two materials carry identical location permissions in the code

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Plastic pipe is prohibited for fuel gas in all locations, including underground service lines buried outside the building

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North Carolina HVAC Exam Prep FREE Sample Exam — Fixed Set

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