NATE Light Commercial Questions Answered Correctly –|
Latest Version 2024/2025
Which of the following measurements would be needed to determine oil furnace
combustion efficiency?
a. net stack temperature and CO2 concentration
b. net stack temperature and CO concentration
c. stack temperature and indoor temperature
d. stack temperature and fuel pressure - ANSWER a. net stack temperature and
CO2 concentration
When combustion is being tested on an oil furnace, high level of smoke and can be
corrected by:
a. Adjusting the barometric damper.
b. Opening the air shutter.
c. Adjusting the primary control.
d. Closing the air shutter. - ANSWER b. Opening the air shutter
A common problem with restaurant units is their location near kitchen exhaust. This
could cause high discharge pressure in the cooling mode because:
a. Return air filter becomes plugged.
b. Grease plugs the evaporator.
c. Grease plugs the condensate line.
d. Grease plugs the condenser coil. - ANSWER d. Grease plugs the condenser
coil.
When a heat pump is in the cooling mode of operation, the check valve at the indoor
coil should be:
a. Modulating.
b. Half open.
c. Fully closed.
d. Fully open. - ANSWER c. Fully closed.
,The technician make a service call in answer to a complaint of little or no cooling
from an R-22 rooftop air conditioning unit. Upon checking pressures when the unit is
running, the technician finds:
· Suction pressure 48 psig
· Discharge pressure 190 psig
· Superheat 0°F
The problem most likely occurs because the:
a. Evaporator coil is iced up.
b. Unit is full of non-condensables.
c. Dirty condenser coil.
d. Unit is overcharged. - ANSWER a. Evaporator coil is iced up.
The result of properly converting a natural gas furnace to LP using the factory kit will:
a. Decrease the pressure and the orifice size
b. Decrease the pressure and increase the orifice size
c. increase the pressure and the orifice size
d. increase the pressure and decrease the orifice size - ANSWER d. increase the
pressure and decrease the orifice size
At least 24 hours before you start up a system that has been shut down for a long
time, you must energize the crankcase heater, in order to:
a. reduce the viscosity of the oil
b. reduce the amount of refrigerant that may be in the compressor
c. warm the compressor so that it will work more efficiently
d. heat the refrigerant so that it will work more efficiently - ANSWER b. reduce the
amount of refrigerant that may be in the compressor
In checking a restaurant, a technician find difficulty in opening the front doors.
Providing that kitchen exhaust and make-up air are balanced properly, which of the
following adjustments should be made?
a. the blower speed should be decreased
b. System BTU capacity should be increased
c. The space temperature set point should be increased
d. The minimum outdoor air setting should be checked - ANSWER d. The
minimum outdoor air setting should be checked
A furnace is rated at 120,000 Btu input, but produces 100,000 Btu output. The
percentage that exists as lost heat is:
a. 12%
b. 17%
c. 22%
d. 20% - ANSWER b. 17%
Air that is pre-mixed with the gas in the burner is called:
, a. primary air
b. dilution air
c. secondary air
d. supply air - ANSWER a. primary air
Velocity pressure is computed by subtracting the static pressure from the:
a. absolute pressure
b. gauge pressure
c. total pressure
d. differential pressure - ANSWER c. total pressure
For a single state LP furnace, the manifold gas pressure to the atmospheric burners
should be a minimum of:
a. 3.5 inches of water column
b. 7 inches of water column
c. 10 inches of water column
d. 13 inches of water column - ANSWER c. 10 inches of water column
With 240-volt, 60-Hz, single- phase power and a 5-kw heater, how many amperes
will be used and how many BTUH of heat will be generated?
a. 10.8 amperes, providing 9,250 BTUH
b. 15.9 amperes, providing 19,576 BTUH
c. 20.8 amperes, providing 17,065 BTUH
d. 20.8 amperes, providing 14,450 BTUH - ANSWER c. 20.8 amperes, providing
17,065 BTUH
While performing a maintenance check of an operating electric furnace with a
missing data plate, the technician needs to determine the total kilowatt consumption
of all elements. Which of the following instruments would normally be used to obtain
data for this calculation?
a. voltmeter and thermometer
b. ohmmeter and voltmeter
c. ohmmeter and ammeter
d. ammeter and voltmeter - ANSWER d. ammeter and voltmeter
On a maintenance check of an electric furnace, a technician notices deterioration of
the wire connections to the elements. The most appropriate course of action is to
replace the:
a. wire, terminals ends, elements, and check the amperage
b. wire and terminal ends and check the amperage
c. fusible links, elements, and check the amperage
d. terminal ends, elements, and check the amperage - ANSWER b. wire and
terminal ends and check the amperage
Latest Version 2024/2025
Which of the following measurements would be needed to determine oil furnace
combustion efficiency?
a. net stack temperature and CO2 concentration
b. net stack temperature and CO concentration
c. stack temperature and indoor temperature
d. stack temperature and fuel pressure - ANSWER a. net stack temperature and
CO2 concentration
When combustion is being tested on an oil furnace, high level of smoke and can be
corrected by:
a. Adjusting the barometric damper.
b. Opening the air shutter.
c. Adjusting the primary control.
d. Closing the air shutter. - ANSWER b. Opening the air shutter
A common problem with restaurant units is their location near kitchen exhaust. This
could cause high discharge pressure in the cooling mode because:
a. Return air filter becomes plugged.
b. Grease plugs the evaporator.
c. Grease plugs the condensate line.
d. Grease plugs the condenser coil. - ANSWER d. Grease plugs the condenser
coil.
When a heat pump is in the cooling mode of operation, the check valve at the indoor
coil should be:
a. Modulating.
b. Half open.
c. Fully closed.
d. Fully open. - ANSWER c. Fully closed.
,The technician make a service call in answer to a complaint of little or no cooling
from an R-22 rooftop air conditioning unit. Upon checking pressures when the unit is
running, the technician finds:
· Suction pressure 48 psig
· Discharge pressure 190 psig
· Superheat 0°F
The problem most likely occurs because the:
a. Evaporator coil is iced up.
b. Unit is full of non-condensables.
c. Dirty condenser coil.
d. Unit is overcharged. - ANSWER a. Evaporator coil is iced up.
The result of properly converting a natural gas furnace to LP using the factory kit will:
a. Decrease the pressure and the orifice size
b. Decrease the pressure and increase the orifice size
c. increase the pressure and the orifice size
d. increase the pressure and decrease the orifice size - ANSWER d. increase the
pressure and decrease the orifice size
At least 24 hours before you start up a system that has been shut down for a long
time, you must energize the crankcase heater, in order to:
a. reduce the viscosity of the oil
b. reduce the amount of refrigerant that may be in the compressor
c. warm the compressor so that it will work more efficiently
d. heat the refrigerant so that it will work more efficiently - ANSWER b. reduce the
amount of refrigerant that may be in the compressor
In checking a restaurant, a technician find difficulty in opening the front doors.
Providing that kitchen exhaust and make-up air are balanced properly, which of the
following adjustments should be made?
a. the blower speed should be decreased
b. System BTU capacity should be increased
c. The space temperature set point should be increased
d. The minimum outdoor air setting should be checked - ANSWER d. The
minimum outdoor air setting should be checked
A furnace is rated at 120,000 Btu input, but produces 100,000 Btu output. The
percentage that exists as lost heat is:
a. 12%
b. 17%
c. 22%
d. 20% - ANSWER b. 17%
Air that is pre-mixed with the gas in the burner is called:
, a. primary air
b. dilution air
c. secondary air
d. supply air - ANSWER a. primary air
Velocity pressure is computed by subtracting the static pressure from the:
a. absolute pressure
b. gauge pressure
c. total pressure
d. differential pressure - ANSWER c. total pressure
For a single state LP furnace, the manifold gas pressure to the atmospheric burners
should be a minimum of:
a. 3.5 inches of water column
b. 7 inches of water column
c. 10 inches of water column
d. 13 inches of water column - ANSWER c. 10 inches of water column
With 240-volt, 60-Hz, single- phase power and a 5-kw heater, how many amperes
will be used and how many BTUH of heat will be generated?
a. 10.8 amperes, providing 9,250 BTUH
b. 15.9 amperes, providing 19,576 BTUH
c. 20.8 amperes, providing 17,065 BTUH
d. 20.8 amperes, providing 14,450 BTUH - ANSWER c. 20.8 amperes, providing
17,065 BTUH
While performing a maintenance check of an operating electric furnace with a
missing data plate, the technician needs to determine the total kilowatt consumption
of all elements. Which of the following instruments would normally be used to obtain
data for this calculation?
a. voltmeter and thermometer
b. ohmmeter and voltmeter
c. ohmmeter and ammeter
d. ammeter and voltmeter - ANSWER d. ammeter and voltmeter
On a maintenance check of an electric furnace, a technician notices deterioration of
the wire connections to the elements. The most appropriate course of action is to
replace the:
a. wire, terminals ends, elements, and check the amperage
b. wire and terminal ends and check the amperage
c. fusible links, elements, and check the amperage
d. terminal ends, elements, and check the amperage - ANSWER b. wire and
terminal ends and check the amperage
