Texas HVAC Exam Prep FREE Sample Exam — Fixed Set

A gauge reads the suction pressure of a system where a liquid-vapor mixture exists in the evaporator. Using the pressure-temperature chart for that refrigerant, the technician can directly determine:

The temperature of the air leaving the supply registers after it has passed through the duct system, plenums, and diffusers into the conditioned space

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The exact charge weight in the system

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The saturation temperature at which refrigerant is boiling in the evaporator

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The temperature of the compressor discharge gas

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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 millivolt wall furnace, the pilot stays lit but the main burner will not open. Open-circuit voltage at the generator reads near its rated value, yet voltage collapses under load. What does that pattern indicate?

The thermostat is calling correctly and the only fault is a dirty main burner that needs brushing before any electrical checks are worth completing on the unit

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The pilot flame is too large and is overheating the generator, so reducing pilot gas alone will restore full load voltage to the gas valve operator circuit

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The gas supply pressure is excessive at the inlet tap, which forces the valve regulator to lock out the main burner while leaving the pilot burning normally

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A weak generator or a high-resistance connection in the circuit

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A technician ohm-tests a cad cell in a brightly burning oil flame and reads a very high resistance, nearly the same as in darkness. The burner locks out on safety shortly after light-off. The correct conclusion is:

The cad cell or its sighting/wiring is faulty, so the control cannot see a flame that is actually present

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The nozzle is oversized for the firing rate, delivering more oil than the chamber was designed for and producing an oversized flame that overheats the cad cell

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The stack draft is excessively high

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The oil supply contains too much air

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A system moves 1,200 CFM. To keep filter face velocity near 300 feet per minute, about how much filter area is needed, and what does that imply for the rack?

About 0.4 square feet, so a very small rack is best because higher velocity forces dust deeper into media for better capture

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About 40 square feet, so the return must be built as a filter wall covering most of one side of the mechanical room itself

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About 12 square feet, calculated by dividing velocity by airflow rather than airflow by the target face velocity value given

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About 4 square feet of filter area

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A flex duct run is supported with thin wire pulled tight at wide intervals, and the duct sags deeply between supports with the core choked where the wire bites in. Name the correct support practice and its purpose.

Support it only at the two ends, since flex duct is self-supporting over any span

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Use the tight wire, but add more of them, since choking the core is how flex is secured, with each additional tight wire pinching the duct further into place so the run cannot shift, sag, or pull loose between supports over time in service

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Hang flex duct from its outer jacket only, letting the inner core hang free inside

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Support flex duct at close intervals with wide straps that cradle the duct without cutting into it, keeping sag minimal, because sag and choked spots add friction and can collect condensate in low points

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An ECM blower does not run. Line power is present at the motor, but no control signal arrives at the motor connector. The correct conclusion is:

Replace the motor and module as a set, because an ECM motor that has power but does not run is always internally failed regardless of its input signal

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Do not condemn the motor; find why the control signal is missing

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Replace the module only, because the module generates its own control signal internally and does not depend on a signal from the furnace control board

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Install a PSC motor in its place without changing the controls, because an ECM motor and a PSC motor respond to the same inputs at the motor leads

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In January a house shows heavy window condensation and RH of 55% indoors at 70°F, with no plumbing or roof leaks found. What is the most likely explanation?

Outdoor winter air leaking in is humidifying the house, because cold outdoor air holds more moisture than warm indoor air and releases it at the windows

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The windows are defective and are generating moisture at the glass, which is why condensation appears there first instead of anywhere else in the rooms

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The furnace humidifier has failed empty and is somehow adding moisture, since window condensation in winter is a standard symptom of too little indoor humidity

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Indoor vapor condensing on cold glass

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A crew is about to work from a scaffold erected beside an air handler. Which condition must be met before the scaffold is used each shift?

The scaffold only needs a fresh inspection when it is first erected, after which daily conditions such as weather and impacts cannot affect its safety

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Workers may use the scaffold while it is still being moved into position, provided they hold the frame and keep their weight near the casters

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Guardrails can be left off the top level whenever ductwork is being passed up, because material handling temporarily overrides fall protection needs

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A competent person inspects it and footing and planking are sound

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A new three-phase scroll compressor starts but is unusually loud, draws low amperage, and produces almost no pressure difference between suction and discharge. What is the most likely cause and correction?

The compressor is running in reverse because two power leads are swapped; correct the phase order and recheck operation

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The system is overcharged; recover half the charge and restart it

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The metering device is stuck closed; replace it before running the compressor again

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The condenser fan is cycling; replace the fan control and leave the compressor wiring alone, then run the system again to see whether the pressure difference returns once fan operation is corrected

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Marcus holds a Class B contractor license and is asked to replace a single 30-ton rooftop cooling unit. What should he do?

Accept the job because the building's total combined load is what matters for licensing, not the size of any single unit being replaced

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Decline that unit because a Class B licensee is limited to cooling systems of 25 tons and under per unit

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Accept the job if he also holds general liability insurance at Class A limits

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Decline only if the heating side exceeds 2 million BTU per hour on that same job

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A gas piping system is being sized with a sizing table using the longest length method. The outlets are at different distances from the meter. On what length must every section of this system be sized?

On the length from the point of delivery to the most remote outlet in the system, applied to each section being sized

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On the length of each individual section only, measured fitting to fitting, with no allowance for the rest of the piping system

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On the length from the point of delivery to the nearest outlet, because that outlet controls the pressure available to all the others

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On the average of the lengths to all outlets, calculated by adding the outlet distances together and dividing by the number of outlets

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Texas HVAC Exam Prep FREE Sample Exam — Fixed Set

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