HVAC NATE Gas Heat Exam Prep (Latest 2024/ 2025
Update) 100% Correct Questions and Verified
Answers| Grade A
3/8 to ½ inch of the end of the thermocouple - ANSWERShould be enveloped by the
pilot flame
A control string is defined as two or more switch contacts connected in a circuit, or
set of circuits, to control a load. In order to troubleshoot a load controlled by a
control string, the technician must first: - ANSWERCheck for proper voltage applied
across the load.
A customer complains the unit is "blowing cold air". The technician determines that
the problem occurs at the end of the heating sequence. The furnace used an
electronic integrated blower control. - ANSWERThe likely problem with the system is
the blower off delay is set too long.
A customer has concerns about carbon monoxide (CO) in their hone. Many of their
reported symptoms indicate there may indeed be a CO problem but on each trip the
technician makes to check their home the technician finds normal CO levels. -
ANSWERCO detector reader/recorder would be appropriate to use for determining if
a problem truly exists.
A damaged section of double wall vent pipe is to be replaced with a section
produced by a different manufacturer: - ANSWERThe installer should check the new
section for compatible locking joints.
A dirty or clogged air filter in an operating gas furnace can cause an: -
ANSWERIncrease temperature rise.
A furnace is inoperative because of a failure in the ignition sequence at the flame
proving stage. To check the flame proving circuit the technician would: -
ANSWERConnect a microampmeter set to DC microamps in the sensor circuit and
operate the furnace.
A gas clothes dryer can interfere with the operation of a nearby natural draft gas
furnace with an atmospheric burner by: - ANSWERStealing combustion air
preventing complete fuel burning.
A gas furnace should reach a steady state - ANSWERBefore taking a combustion test
A gas furnace with a standing pilot uses a flame switch for proving pilot flame. -
ANSWERSeveral millivolts are generated by the flame.
A line voltage fuse is sized to protect from: - ANSWERExcessive voltage
, A meter reading microfarads is used to: - ANSWERCheck a run capacitor with a
capacitance tester.
A packaged unit in a two story installation is to be located at ground level with
ductwork running up the outside wall to a chase in the second floor. - ANSWERThe
precautions need to be taken with outside ductwork is it must be insulated and
weatherproofed.
A standing pilot furnace uses a relay for controlling the supply blower. On a call for
heat, the burner lights, the fan control closes, but the blower does not run. A check
of voltage at the blower relay coil shows 24V. The load side measures 0V. The
technician should replace what: - ANSWERFan relay.
A system airflow check determines that supply static is 0.15 in. W.C. and return static
is a negative 0.55 in. W.C. these readings tell the technician: - ANSWERThe difference
between supply static and return static is unacceptably low.
A system that is oversized for the load: - ANSWERWill cause the unit to short cycle.
A technician is installing a gas furnace and the customer has decided not to install an
air conditioner. Making this decision, the affect it will have on the installation of the
supply ductwork is: - ANSWERLeave adequate space should be allowed for addition
of a coil in the future when feasible.
A technician measures the return air temperature of a 100,000 BTU output gas
furnace to be 65°F and the supply side air temperature is 135°F: - ANSWERThe CFM
would be 1323.
A technician receives a call that a gas furnace is running constantly in heating and
cannot be shut off. While checking the thermostat, the technician observes the
burner shuts off by removing the wire on the R terminal on the thermostat subbase.
- ANSWERMost likely there is a short in the thermostat subbase.
A technician should consult WHAT to make an accurate residential load calculation. -
ANSWERManual J is the ACCA manual.
A technician wishes to determine the air flow of a gas furnace on startup using the
temperature rise method, the following conditions exist: - ANSWERThe gas meter
has been clocked and the flow rate has been determined~The gas heating value is
known~The heat rise across the heat exchanger is measured~Next he needs to
calculate the CFM using a formula.
A thermopile system usually generates its own control circuit voltage of: -
ANSWER750 mV.
A transformer with a 24V secondary repeatedly fails. The technician determines the
load in the secondary circuit to be - ANSWER2 amps
Update) 100% Correct Questions and Verified
Answers| Grade A
3/8 to ½ inch of the end of the thermocouple - ANSWERShould be enveloped by the
pilot flame
A control string is defined as two or more switch contacts connected in a circuit, or
set of circuits, to control a load. In order to troubleshoot a load controlled by a
control string, the technician must first: - ANSWERCheck for proper voltage applied
across the load.
A customer complains the unit is "blowing cold air". The technician determines that
the problem occurs at the end of the heating sequence. The furnace used an
electronic integrated blower control. - ANSWERThe likely problem with the system is
the blower off delay is set too long.
A customer has concerns about carbon monoxide (CO) in their hone. Many of their
reported symptoms indicate there may indeed be a CO problem but on each trip the
technician makes to check their home the technician finds normal CO levels. -
ANSWERCO detector reader/recorder would be appropriate to use for determining if
a problem truly exists.
A damaged section of double wall vent pipe is to be replaced with a section
produced by a different manufacturer: - ANSWERThe installer should check the new
section for compatible locking joints.
A dirty or clogged air filter in an operating gas furnace can cause an: -
ANSWERIncrease temperature rise.
A furnace is inoperative because of a failure in the ignition sequence at the flame
proving stage. To check the flame proving circuit the technician would: -
ANSWERConnect a microampmeter set to DC microamps in the sensor circuit and
operate the furnace.
A gas clothes dryer can interfere with the operation of a nearby natural draft gas
furnace with an atmospheric burner by: - ANSWERStealing combustion air
preventing complete fuel burning.
A gas furnace should reach a steady state - ANSWERBefore taking a combustion test
A gas furnace with a standing pilot uses a flame switch for proving pilot flame. -
ANSWERSeveral millivolts are generated by the flame.
A line voltage fuse is sized to protect from: - ANSWERExcessive voltage
, A meter reading microfarads is used to: - ANSWERCheck a run capacitor with a
capacitance tester.
A packaged unit in a two story installation is to be located at ground level with
ductwork running up the outside wall to a chase in the second floor. - ANSWERThe
precautions need to be taken with outside ductwork is it must be insulated and
weatherproofed.
A standing pilot furnace uses a relay for controlling the supply blower. On a call for
heat, the burner lights, the fan control closes, but the blower does not run. A check
of voltage at the blower relay coil shows 24V. The load side measures 0V. The
technician should replace what: - ANSWERFan relay.
A system airflow check determines that supply static is 0.15 in. W.C. and return static
is a negative 0.55 in. W.C. these readings tell the technician: - ANSWERThe difference
between supply static and return static is unacceptably low.
A system that is oversized for the load: - ANSWERWill cause the unit to short cycle.
A technician is installing a gas furnace and the customer has decided not to install an
air conditioner. Making this decision, the affect it will have on the installation of the
supply ductwork is: - ANSWERLeave adequate space should be allowed for addition
of a coil in the future when feasible.
A technician measures the return air temperature of a 100,000 BTU output gas
furnace to be 65°F and the supply side air temperature is 135°F: - ANSWERThe CFM
would be 1323.
A technician receives a call that a gas furnace is running constantly in heating and
cannot be shut off. While checking the thermostat, the technician observes the
burner shuts off by removing the wire on the R terminal on the thermostat subbase.
- ANSWERMost likely there is a short in the thermostat subbase.
A technician should consult WHAT to make an accurate residential load calculation. -
ANSWERManual J is the ACCA manual.
A technician wishes to determine the air flow of a gas furnace on startup using the
temperature rise method, the following conditions exist: - ANSWERThe gas meter
has been clocked and the flow rate has been determined~The gas heating value is
known~The heat rise across the heat exchanger is measured~Next he needs to
calculate the CFM using a formula.
A thermopile system usually generates its own control circuit voltage of: -
ANSWER750 mV.
A transformer with a 24V secondary repeatedly fails. The technician determines the
load in the secondary circuit to be - ANSWER2 amps
