CCS Ventilation & Draft Systems 2

Question 1

What phenomenon occurs when outside air temperature is warmer than flue gas temperature, causing poor draft?

Accepted Answer

Thermal inversion

Answer

Thermal inversion happens when outdoor temperatures exceed flue gas temperatures, eliminating the buoyancy difference needed to sustain upward draft.

Question 2

A chimney serving a high-efficiency appliance (90%+) requires special venting because flue gases are:

Accepted Answer

Too cool and moist, risking condensation

Answer

High-efficiency appliances extract so much heat that exhaust gases exit at low temperatures, often below the dew point, causing acidic condensation in the flue.

Question 3

Which venting category describes a gas appliance with positive vent pressure and likely to produce condensate?

Accepted Answer

Category IV

Answer

Category IV appliances operate under positive vent pressure and produce condensate, requiring sealed, corrosion-resistant vent systems.

Question 4

The term 'available draft' refers to the draft measured at the:

Accepted Answer

Breech or flue entry point

Answer

Available draft is measured at the breech or flue entry point, representing the actual suction available to pull combustion gases from the appliance.

Question 5

When two appliances share a common flue, which condition most likely causes cross-contamination of flue gases?

Accepted Answer

The flue is oversized relative to combined appliance input

Answer

An oversized common flue creates low velocity and insufficient draft, allowing exhaust from one appliance to spill and enter the connected appliance's heat exchanger.

(CCS) Certified Chimney Sweeper Practice Test

(CCS) Certified Chimney Sweeper Practice Test

CCS Ventilation & Draft Systems 2