NATE Gas Heat Practice Guide GUARANTEED PASS !!
What precautions are required when mounting any gas furnace on a wood platform in an attic? -
(ANSWER)None
The gas control valve may be damaged if exposed to an inlet pressure above what? - (ANSWER)14 inch W.C.
How many elbows and joints should a vent connector have? - (ANSWER)As few as possible to reduce
resistance of flue gases.
Under what conditions, if any may the technician route the exhaust of the furnace into the exhaust vent of the
water heater: - (ANSWER)Under no conditions may you use the water heater exhaust vent.
How may a technician terminate the intake and exhaust for proper operation of a high efficiency gas furnace
when using scheduled 40 PVC pipe: - (ANSWER)By using the specific manufacturers termination kit or make
one to meet their requirements.
When suspended with metal strap and no saddle, flexible duct should be: - (ANSWER)supported with a
minimum strap width of
1/2".
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: - (ANSWER)Leave adequate
space should be allowed for addition of a coil in the future when feasible.
Leveling of a Mercury bulb is __________ - (ANSWER)Critical
Spray-type atomizing humidifiers are installed to do what? - (ANSWER)Discharge moisture into the supply
duct.
Electronic air cleaners (EAC) installed in a gas furnace system should be wired so they: - (ANSWER)Only
operate any time the EAC On-Off switch is turned to ON.
Page 1 of 16
,The LP gas manifold pressure is commonly what? - (ANSWER)10 to 11 in. W.C.
The polarity of a 120V gas furnace equipped with electronic flame rectification is important because: -
(ANSWER)The ignition control may not prove flame.
Using a voltmeter, a technician can determine voltage drop at a gas furnace: - (ANSWER)With the furnace not
operating and then with the furnace operating.
The setting on a 4 speed PSC blower motor can be changed by changing the: - (ANSWER)Motor tap
connection.
When starting up a dual system, the temperature rise method for determining airflow cannot be used with
compressor cycle of the heat pump because: - (ANSWER)The capacity of the system varies too much with
outdoor temperature.
The flame pattern a technician would expect to see on a properly operating single stage gas furnace equipped
with "in shot" type burner is a: - (ANSWER)Hard and forceful flame with a light blue appearance and little or
no yellow.
What is recommended method for a pressurization leak test of a fuel gas pipe? - (ANSWER)Compressed air
What is a diaphragm type differential pressure gauge used for? - (ANSWER)Measure air pressure.
The pressure reading on a manometer is expressed in: - (ANSWER)Inches of water.
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. Calculate the CFM. - (ANSWER)The CFM would be 1323.
A dirty or clogged air filter in an operating gas furnace can cause what? - (ANSWER)Increase temperature rise.
What can bent vanes on a direct drive blower wheel in a gas furnace cause? - (ANSWER)Loss in airflow,
excessive blower motor wear, and increase noise.
Page 2 of 16
, A gas clothes dryer can interfere with the operation of a nearby natural draft gas furnace with an atmospheric
burner by: - (ANSWER)Stealing combustion air preventing complete fuel burning.
During a preventive maintenance check of a gas furnace, what should always be checked for on the ductwork? -
(ANSWER)Ductwork should always be checked for leaks and damage.
When performing a cycle check during a preventive maintenance call, the technician should: -
(ANSWER)~First check with the owner of the equipment for their opinion of performance.
~The next step is to turn the unit off at the thermostat system switch. ~Next the technician should set the FAN
switch to ON and check that the blower is running.
What measurements are required to calculate the CFM of a gas furnace are? - (ANSWER)~Entering air
temperature
~Leaving air temperature
~Outdoor ambient and rated capacity.
The reason for checking the temperature rise across the heat exchanger of a gas furnace is to: -
(ANSWER)Compare temperature differential to nameplate rating.
The technician is checking the operation of an induced draft furnace with an atmospheric burner and a direct
ignition system. On a call for heat the sequence is what? - (ANSWER)~Vent blower comes on
~Igniter glows
~Main burner does not light
~The next check would be the gas supply and/or gas valve
The technician is servicing a gas furnace located in a basement and the complaint is "not enough heat". The
following conditions exist: - (ANSWER)Properly sized furnace is operating correctly
Temperature rise is within specification
Filter is clean and CFM from blower is proper
The most likely problem with this system is the air side is leaking at one or more supply ducts.
Page 3 of 16
What precautions are required when mounting any gas furnace on a wood platform in an attic? -
(ANSWER)None
The gas control valve may be damaged if exposed to an inlet pressure above what? - (ANSWER)14 inch W.C.
How many elbows and joints should a vent connector have? - (ANSWER)As few as possible to reduce
resistance of flue gases.
Under what conditions, if any may the technician route the exhaust of the furnace into the exhaust vent of the
water heater: - (ANSWER)Under no conditions may you use the water heater exhaust vent.
How may a technician terminate the intake and exhaust for proper operation of a high efficiency gas furnace
when using scheduled 40 PVC pipe: - (ANSWER)By using the specific manufacturers termination kit or make
one to meet their requirements.
When suspended with metal strap and no saddle, flexible duct should be: - (ANSWER)supported with a
minimum strap width of
1/2".
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: - (ANSWER)Leave adequate
space should be allowed for addition of a coil in the future when feasible.
Leveling of a Mercury bulb is __________ - (ANSWER)Critical
Spray-type atomizing humidifiers are installed to do what? - (ANSWER)Discharge moisture into the supply
duct.
Electronic air cleaners (EAC) installed in a gas furnace system should be wired so they: - (ANSWER)Only
operate any time the EAC On-Off switch is turned to ON.
Page 1 of 16
,The LP gas manifold pressure is commonly what? - (ANSWER)10 to 11 in. W.C.
The polarity of a 120V gas furnace equipped with electronic flame rectification is important because: -
(ANSWER)The ignition control may not prove flame.
Using a voltmeter, a technician can determine voltage drop at a gas furnace: - (ANSWER)With the furnace not
operating and then with the furnace operating.
The setting on a 4 speed PSC blower motor can be changed by changing the: - (ANSWER)Motor tap
connection.
When starting up a dual system, the temperature rise method for determining airflow cannot be used with
compressor cycle of the heat pump because: - (ANSWER)The capacity of the system varies too much with
outdoor temperature.
The flame pattern a technician would expect to see on a properly operating single stage gas furnace equipped
with "in shot" type burner is a: - (ANSWER)Hard and forceful flame with a light blue appearance and little or
no yellow.
What is recommended method for a pressurization leak test of a fuel gas pipe? - (ANSWER)Compressed air
What is a diaphragm type differential pressure gauge used for? - (ANSWER)Measure air pressure.
The pressure reading on a manometer is expressed in: - (ANSWER)Inches of water.
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. Calculate the CFM. - (ANSWER)The CFM would be 1323.
A dirty or clogged air filter in an operating gas furnace can cause what? - (ANSWER)Increase temperature rise.
What can bent vanes on a direct drive blower wheel in a gas furnace cause? - (ANSWER)Loss in airflow,
excessive blower motor wear, and increase noise.
Page 2 of 16
, A gas clothes dryer can interfere with the operation of a nearby natural draft gas furnace with an atmospheric
burner by: - (ANSWER)Stealing combustion air preventing complete fuel burning.
During a preventive maintenance check of a gas furnace, what should always be checked for on the ductwork? -
(ANSWER)Ductwork should always be checked for leaks and damage.
When performing a cycle check during a preventive maintenance call, the technician should: -
(ANSWER)~First check with the owner of the equipment for their opinion of performance.
~The next step is to turn the unit off at the thermostat system switch. ~Next the technician should set the FAN
switch to ON and check that the blower is running.
What measurements are required to calculate the CFM of a gas furnace are? - (ANSWER)~Entering air
temperature
~Leaving air temperature
~Outdoor ambient and rated capacity.
The reason for checking the temperature rise across the heat exchanger of a gas furnace is to: -
(ANSWER)Compare temperature differential to nameplate rating.
The technician is checking the operation of an induced draft furnace with an atmospheric burner and a direct
ignition system. On a call for heat the sequence is what? - (ANSWER)~Vent blower comes on
~Igniter glows
~Main burner does not light
~The next check would be the gas supply and/or gas valve
The technician is servicing a gas furnace located in a basement and the complaint is "not enough heat". The
following conditions exist: - (ANSWER)Properly sized furnace is operating correctly
Temperature rise is within specification
Filter is clean and CFM from blower is proper
The most likely problem with this system is the air side is leaking at one or more supply ducts.
Page 3 of 16
