Chapter 10 Flue and Vent Criteria

Question 1

what are the two most important criteria when designing or building a vent system

Answer 1

the flue gas temperature leaving the gas appliance

the gas venting system pressure (can be positive or negative

Question 2

what are the 4 categories of venting systems

Answer 2

1. non-positive vent static pressure, vent gas temperature does not produce excess condensation on the vent (National Fuel Gas Code)
2. Non-positive vent static pressure, vent gas temp does produce excessive condensation in the vent
3. positive vent static pressure, vent gas temp does not produce excessive condensation in the vent
4. positive vent static pressure, vent gas temp does produce excessive condensation in the vent

Question 3

Which categories of venting systems must be gas tight

Answer 3

3 and 4 - the ones that have positive vent static pressure

Question 4

which categories of venting systems must be corrosive resistant and water tight

Answer 4

2 and 4 - the ones that create excessive condensation

Question 5

what is the balanced-vent principle (aka direct-vent)

Answer 5

when the entrance to the intake air duct and exhaust duct are located close to each other the affects of wind gusts are cancelled

Question 6

what are 3 types of venting materials

Answer 6

single wall vent systems
type “B” vent systems (double wall)
synthetic materials

Question 7

What is a single wall vent system

Answer 7

one which allows the flue gasses in a vent pipe to be cooled rapidly. this may increase the amount of condensation created. Not allowed in colder climates

Question 8

What is a double wall vent system

Answer 8

can only be used on gas-fired applications
operating with negative pressure and flue gas temp below 550deg F
may not be used on category 2 and 4 applications

Question 9

which categories can employ synthetic venting

Answer 9

categories 2 and 4