NATE AIR DISTRIBUTION QUESTIONS AND ANSWERS
What is the funtion of a transformer in a gas furnace application - Answers- It reduces
line voltage to control voltage.
On a call for heat, the thermostat energizes the ________ terminal. - Answers- 'W'
What is the function of the inducer in a gas furnace. - Answers- It brings in air for
combustion.
Rollout limit switches are located in the _______________ . - Answers- burner area
Which of the following statements is true regarding inshot burners? - Answers- They
require a separate flame carryover channel.
A furnace with an AFUE (Annual Fuel Utilization Efficiency) of 90% or higher has
________________ . - Answers- both primary and secondary heat exchangers.
For natural gas applications, an ideal line pressure is ____________ in. w.g. - Answers-
7.0 in. w.g.
For natural gas applications, the manifold pressure typically is set at __________ in.
w.g. - Answers- 3.5 in. w.g.
In a gas furnace application, ESP refers to the __________________ . - Answers-
resistance to air flow in the supply and return ducts.
After clocking a natural gas meter in seconds per 3ft, what is the formula to determine
the actual burning rate of a furnace. - Answers- (3600//Total seconds to consume 1 ft3
of gas.) X 1050Btu's/ft3
Note: A correction factor my have to be used on some meters, especially on commercial
applications. This is usually around 3.04 and can be found with the formula Inlet gas
pressure psia+14.7/14.7
You suspect an evaporator coil is restricted, you take static pressure across the coil to
determine if it is. What difference would you be expecting with a dry coil, then with a wet
coil? - Answers- .2 to.25 in. w.g. dry - .3 in. w.g. wet
If the duct work, return or supply, pressure drop is in excess of _________ it may be
undersized. - Answers- 0.1 to 0.15 in. w.g.
Name the four most common types of gas furnace ignition systems. - Answers- Hot
surface ignition, Hot surface to pilot ignition, Spark to pilot ignition, Direct spark ignition.
What is the funtion of a transformer in a gas furnace application - Answers- It reduces
line voltage to control voltage.
On a call for heat, the thermostat energizes the ________ terminal. - Answers- 'W'
What is the function of the inducer in a gas furnace. - Answers- It brings in air for
combustion.
Rollout limit switches are located in the _______________ . - Answers- burner area
Which of the following statements is true regarding inshot burners? - Answers- They
require a separate flame carryover channel.
A furnace with an AFUE (Annual Fuel Utilization Efficiency) of 90% or higher has
________________ . - Answers- both primary and secondary heat exchangers.
For natural gas applications, an ideal line pressure is ____________ in. w.g. - Answers-
7.0 in. w.g.
For natural gas applications, the manifold pressure typically is set at __________ in.
w.g. - Answers- 3.5 in. w.g.
In a gas furnace application, ESP refers to the __________________ . - Answers-
resistance to air flow in the supply and return ducts.
After clocking a natural gas meter in seconds per 3ft, what is the formula to determine
the actual burning rate of a furnace. - Answers- (3600//Total seconds to consume 1 ft3
of gas.) X 1050Btu's/ft3
Note: A correction factor my have to be used on some meters, especially on commercial
applications. This is usually around 3.04 and can be found with the formula Inlet gas
pressure psia+14.7/14.7
You suspect an evaporator coil is restricted, you take static pressure across the coil to
determine if it is. What difference would you be expecting with a dry coil, then with a wet
coil? - Answers- .2 to.25 in. w.g. dry - .3 in. w.g. wet
If the duct work, return or supply, pressure drop is in excess of _________ it may be
undersized. - Answers- 0.1 to 0.15 in. w.g.
Name the four most common types of gas furnace ignition systems. - Answers- Hot
surface ignition, Hot surface to pilot ignition, Spark to pilot ignition, Direct spark ignition.
