FC Safety Standards & Codes for Furnace Systems 3

Question 1

A Category IV furnace vents with positive pressure and produces condensate. Which vent material is specifically listed for this application?

Accepted Answer

Listed PVC or CPVC vent pipe

Answer

Category IV appliances require vent systems listed for positive pressure and condensate resistance, such as Schedule 40 PVC or CPVC approved for this use.

Question 2

What is the purpose of the dielectric union required when connecting a gas furnace to the gas supply piping that contains dissimilar metals?

Accepted Answer

To prevent galvanic corrosion between dissimilar metals

Answer

Dielectric unions electrically isolate dissimilar metals in piping to prevent galvanic corrosion that could deteriorate connections.

Question 3

Under the International Residential Code (IRC), what is the minimum height of a furnace room door that opens into a garage where the furnace contains an ignition source?

Accepted Answer

The furnace must be elevated 18 inches above the garage floor

Answer

The IRC requires that appliances with ignition sources installed in garages be elevated at least 18 inches above the floor to keep ignition sources above potential fuel vapors.

Question 4

Which safety control is required on all gas furnaces to shut off gas flow if the pilot flame is extinguished?

Accepted Answer

Thermocouple or flame sensor (flame supervision device)

Answer

A flame supervision device such as a thermocouple (standing pilot) or flame sensor (electronic ignition) shuts off gas if the pilot or burner flame is lost.

Question 5

What is the maximum permissible CO concentration in parts per million (ppm) in the flue gas of a properly operating gas furnace, as referenced by most safety standards?

Accepted Answer

400 ppm air-free

Answer

Most U.S. standards, including ANSI Z21.47, allow a maximum of 400 ppm CO air-free in furnace flue gases under normal operating conditions.

(FC) Furnace Installation and Maintenance Certification Practice Test

(FC) Furnace Installation and Maintenance Certification Practice Test

FC Safety Standards & Codes for Furnace Systems 3