Boiler Types Flashcards

What is an open-flued boiler?

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

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.

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

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

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.

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

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

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.

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

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

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.

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

Answer: Predominantly blue with a small yellow tip

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

What does 'thermal store' refer to in hot water system terminology?

Answer: A large insulated cylinder that stores primary circuit water, heating DHW indirectly via a heat exchanger

A thermal store is a large primary water storage cylinder that acts as a heat battery; domestic hot water is heated indirectly by passing mains water through an internal coil or heat exchanger.