Install Mod Week 2 Unit 57 Gas Furnace Installation HW

What is the first step in preparing to install a new furnace?

• The first step is to determine the appropriate location.

• Find the correct size of system

• Test the breakers

• Take a smoke break 15 min before you start

What is the difference between natural gas and propane?

• Natural gas is mostly methane and a little ethane, has a specific gravity 0.6, and a heat capacity around 1000 BTU/hr. Propane has a specific gravity of 1.5 and a heat capacity of 2500 BTU/hr

• Usually Natural GAS is adjusted at the gas valve to 3.8 " W.C.

• Usually Propane is adjust at the gas valve to 11.6 " W.C.

• Natural Gas smells like a rotten egg

What is the most common manifold pressure for natural gas furnaces?

• 3.5 inches WC

• 10 inches WC

• 5 inches WC

• higher the pressure the higher the gas bill

What is the most common manifold pressure for propane furnaces?

• 11 inches WC

• 3.5 inches WC

• 5 inches WC

• Propane allows you too cook on your furnace while heating your home

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

• 20 cubic feet per hour

• 10 cubic feet per hour

Use the gas flow rate calculated from question 5 to determine the input in BTU/hr if the heating capacity of the gas is 950 BTU/ft3.

• yep

• 60 cubic feet x 950 BTU/cubic foot = 57,000 BTUs per hour

What is the correct vent size for a 50,000 BTU/hr input induced draft furnace with a 15-foot lateral run and a 30-foot vent height?

• 3” or 4”

• 6" or 8"

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

• 100,00 BTU/hr input

• 120,000 BTU/hr input

• 50,000 BTU/hr input

What size should the combustion air openings be for a room with an 80,000 BTU/hr input furnace and a 35,000 BTU/hr water heater if the openings are opening directly into a ventilated attic and a ventilated crawlspace?

• 80,000 + 35,000 = 115,000 total input 115,000 / 4,000 = 28.75 square inches each

• Do the math

What size should the openings be in question 9 if the air is traveling through horizontal ducts to the outside?

• 80,000 + 35,000 = 115,000 total input 115,000 / 2,000 = 57.5 square inches each

• Math