CCN1 Combustion and Ventilation 2

Question 1

When testing the combustion performance of a gas appliance, what does a high CO/CO₂ ratio indicate?

Accepted Answer

Incomplete combustion is occurring

Answer

Perfect combustion conditions

Answer

Excess air is entering the appliance

Answer

The flue is working efficiently

Question 2

What is 'vitiation' in the context of gas appliance operation?

Accepted Answer

The progressive reduction of oxygen in a room due to an appliance consuming air for combustion

Answer

The process of igniting a gas burner

Answer

The corrosion of flue components

Answer

The measurement of gas pressure at the meter

Question 3

What is the minimum free area of a permanent air vent required for a flueless gas appliance such as a cooker with a rated input of 15 kW?

Accepted Answer

5 cm² per kW of rated net input

Answer

No ventilation required below 20 kW

Answer

5 cm² per kW of rated input above 7 kW

Answer

Depends on the room volume only

Question 4

What colour flame indicates correct combustion on a natural gas burner?

Accepted Answer

Predominantly blue with a clearly defined inner cone

Answer

Yellow with orange tips

Answer

Red with flickering

Answer

White with sparking

Question 5

What happens to the products of combustion from a decorative fuel effect (DFE) gas fire?

Accepted Answer

They are discharged through a conventional chimney or flue

Answer

They are all released into the room as it is a flueless appliance

Answer

They pass through a catalytic converter

Answer

They are recycled back into the burner

Question 6

What is the purpose of a spillage test on an open-flued gas appliance?

Accepted Answer

To verify that combustion products are being safely drawn into the flue and not spilling into the room

Answer

To check for gas leaks on the supply pipework

Answer

To measure the gas pressure at the burner

Answer

To test the thermocouple response time