Flue Size Selection Guide

The chimney size should be as recommended by the appliance manufacturer. Where there is a requirement for a flue diameter smaller than the appliance spigot, then the operational requirements of the appliance and the configuration of the flue must satisfy the flue sizing requirements of DIN4705.

For more information contact the installer helpline. The information and sizes below are provided as a nominal guide only. Flue sizing for appliances, particularly commercial/industrial applications, will vary depending on siting details and appliance manufacturer’s instructions and design criteria. These will override the sizing guide and reference must be made to appliance manufacture. For Inglenook and non-standard openings, the diameter of the flue must be at least 15% of the cross sectional area of the fireplace opening.

Use the wizard to determine the required size,
or if you prefer you can refer to the table below.

Flue Sizing Wizard

	80 mm	100 mm	130 mm	150 mm	180 to 400mm
Gas - Atmospheric Boiler
Input up to 25kW		•
Input 25kW-40kW			•
Input 40kW-60kW				•
Gas - Commercial/Industrial Boilers
Input up to 50kW to 70kW					•2
Gas Fires
'Radiant' - BS7977-1 2002			•
'Inset' - BS7977-1 2002			•1		•1
'Backboiler' - BS7977-2 2003			•
Gas Water Heaters
Input up to 25kW	•	•
Input 25kW to 55kW			•
Input 55kW to 60kW				•
Input over 60kW					•2
Gas Warm Air Units
Input up to 18kW		•
Input 18kW to 35kW			•
Input 35kW to 60kW				•
Input over 60kW					•2
Gas Stove/Cooker		•2	•2	•2
Kerosene (28 sec Class C2) Heating Boiler
Output up to 25kW		•
Input 25kW to 45kW			•
Input 45kW to 70kW				•
Kerosene Stove/Cooker		•3	•3	•3
Kerosene Water Heater
Input up to 41kW				•
Kerosene Visual Effect Stove
Input up to 17kW		•3	•3

NOTES
1 Subject to appliance manufacturer's testing criteria.
2 Subject to manufacturer's input rating and chimney height.
3 Subject to manufacturer's output rating and chimney height.
4 Min 300mm depending on opening, chimney size and height.
S Smokeless fuel only.
SC Smokeless fuel or coal.

This information and sizes are provided as a nominal guide only. Flue sizing for appliances, particularly commercial/industrial applications will vary depending on siting details and appliance manufacturer's instructions and design criteria. These will override the sizing guide below and reference must be made to appliance manufacturer.

Use the wizard to determine the required size,
or if you prefer you can refer to the table below.

Flue Sizing Wizard

	100 mm	130 mm	150 mm	180 mm	200 mm	230 mm	250 to 400mm
Gas Boiler - Forced Draught
Input up to 25kW	•
Input 25kW-45kW		•
Input 45kW-50kW			•
Input 50kW-75kW				•
Input 75kW-100kW					•
Input over 100kW						•	•2
Gas Fires
'Inset' to BS7977-1 2002				•1
'Decorative' to BSEN 509:2000				•
Gas Oil (35 sec Class D) Heating Boiler
Output up to 25kW	•
Input 25kW to 45kW		•
Input 45kW to 70kW			•
Input 70kW to 100kW				•
Output over 100kW					•3	•3	•3
Solid Fuel Heating Boiler
Output up to 20kW			•S	•SC
Output 20kW to 30kW				•S	•SC	•SC
Output 30kW to 60kW					•SC	•SC	•SC
Open Fires (Standard opening) 500mm x 550mm					•200 mm
'Avant Garde' Feature Open Fires							•4
Room Heaters			•S
Wood burning Stoves/Cookers. Use only seasoned wood which has been stored 1/2 years in dry conditions.			•	•200 mm
Inglenook or nonstandard opening. The Cross sectional area of the chimney liner must be a minimum of 15% of the total cross sectional area of the fireplace opening.						•230 mm

Key to annotation on tables
1 Subject to appliance manufacturer's testing criteria.
2. Subject to manufacturer's input rating and chimney height.
3. Subject to manufacturer's output rating and chimney height.
4. Min 300mm depending on opening, chimney size and height.
S Smokeless fuel only.
SC Smokeless fuel or coal.