OFTEC Flue Systems for Oil

Question 1

What is the primary purpose of a flue system on an oil-fired appliance?

Accepted Answer

To safely discharge combustion products to the outside atmosphere

Answer

The flue system safely removes combustion products (CO2, CO, water vapour, and other gases) from the appliance and discharges them to the outside air at a safe location, preventing them from entering the occupied building.

Question 2

What is the difference between a conventional flue and a balanced flue for oil appliances?

Accepted Answer

A conventional flue draws combustion air from the room; a balanced flue draws air from outside

Answer

A conventional (open) flue draws combustion air from the room and expels gases through the flue. A balanced (room-sealed) flue has a concentric or twin-pipe arrangement that draws air from outside and expels gases outside, making it independent of room air.

Question 3

What is the minimum height a vertical oil flue terminal must be above a flat roof?

Accepted Answer

600mm above the roof surface within 1.5m of the terminal

Answer

A vertical flue terminal must be at least 600mm above any part of the roof that is within 1.5 metres of the terminal. This ensures adequate dispersal of combustion products and prevents downdraught from building structures.

Question 4

Why must oil flue systems have a minimum number of bends?

Accepted Answer

Each bend increases resistance to gas flow and reduces the available draught

Answer

Each bend in a flue system creates resistance to gas flow, reducing the natural draught that drives combustion products through the system. Excessive bends can cause spillage of combustion gases into the room. The maximum is usually 2 bends.

Question 5

What is the maximum horizontal run allowed for an oil flue pipe before it must rise vertically?

Accepted Answer

Generally 3 metres, with a minimum upward slope of 1 in 12

Answer

Horizontal flue runs should generally not exceed 3 metres and must slope upward at a minimum of 1 in 12 (approximately 5°) away from the appliance. This ensures combustion gases flow naturally toward the terminal.

OFTEC Practice Test

OFTEC Practice Test

OFTEC Flue Systems for Oil