Basic Stuff
What is the first step in preparing to install a new furnace?
The first step is to determine the appropriate location
Where do you measure the temperature when checking furnace temperature rise?
Return air and supply air as near the furnace as possible. Make sure the thermometer is not directly in line with heat exchanger when measuring the supply air.
How can the speed of the indoor fan (blower) be changed on a furnace control board
The speed of the indoor fan can often be changed either moving programming jumpers or by changing DIP switches.
What is the red terminal for
Power
What is the most common manifold pressure for natural gas furnaces?
3.5 inches WC
What is the temperature rise of a furnace with a supply air temperature of 130°F and a return air temperature of 75°F?
130° – 75° = 55°F rise
What is the first step before checking the gas manifold pressure to the furnace?
The first step before checking the gas manifold pressure to the furnace is to check the gas supply line pressure.
What is the Green terminal for
Fan
What is the most common manifold pressure for propane furnaces?
11 inches WC
How can the temperature rise of a furnace be reduced if the temperature rise is too high?
Increasing the air flow will reduce the furnace temperature rise.
Why is a direct vent more efficient than a non-direct vent
When the combustion air is taken directly from the space, the furnace is using heated indoor air for combustion that will be exhausted outside.
What is the yellow terminal for
cooling
A technician is clocking the gas usage of a gas furnace. It takes 30 seconds for the 1/2-foot dial to make 1 revolution. What is the rate of gas flow in cubic feet per hour?
60 cubic feet per hour
What precaution needs to be taken when installing a condensing furnace in an attic over a finished ceiling?
Install a drain pan under the entire furnace to prevent damage to the ceiling in the event of a plugged drain.
What happens to the speed of the induced draft fan when a two stage furnace switches from a low firing rate to a high firing rate?
The speed of the induced draft fan will increase.
What is the white terminal for
Heat
What is the smallest fan assisted furnace that can be connected to an existing 6-inch type B vent that is 30 feet high with a lateral run of 15 feet?
70,000 BTU/hr input
Explain what is meant by a concentric vent pipe
A concentric vent pipe may appear to be only one pipe but it’s really one pipe inside the other which still qualifies for a two-pipe system.
How is the correct manifold pressure for any particular installation determined?
Use the manufacturer's installation chart to determine the manifold pressure based on altitude and gas heating value.
What is the B and O terminal for on a heat pump capatable thermostat