CENWAT Boiler Types 3

Question 1

What is an open-flued boiler?

Accepted Answer

A boiler that draws combustion air from the room in which it is installed

Answer

An open-flued boiler draws combustion air from the room (indoor air) and discharges flue gases via a flue to atmosphere; adequate room ventilation is essential.

Question 2

What is a room-sealed (balanced flue) boiler?

Accepted Answer

A boiler that draws combustion air from outside and discharges flue gases externally, sealed from the room

Answer

A room-sealed boiler draws all combustion air directly from outside and discharges flue gases externally, completely isolated from the indoor air; no room ventilation is required for combustion.

Question 3

What is a fan-assisted flue (positive pressure flue) on a boiler?

Accepted Answer

A flue system where a fan forces flue gases out and draws in combustion air, allowing flexible flue routing

Answer

Fan-assisted (positive flue) systems use an integral fan to overcome resistance in longer or complex flue runs, giving greater flexibility in siting the boiler.

Question 4

What is the purpose of the flue gas analyser check during boiler commissioning?

Accepted Answer

To verify combustion efficiency and CO2/O2 levels are within manufacturer's specification

Answer

A flue gas analysis confirms that combustion is efficient and safe, checking CO2, O2 and CO levels against the manufacturer's specification to ensure correct air/gas ratio.

Question 5

What colour is the flame on a correctly burning gas boiler burner?

Accepted Answer

Predominantly blue with a small yellow tip

Answer

A correctly burning gas flame is predominantly blue, indicating complete combustion. A yellow or orange flame indicates incomplete combustion and possible carbon monoxide production.

ACS CENWAT Practice Test

ACS CENWAT Practice Test

CENWAT Boiler Types 3