Boiler - Exhaust Velocity

This tool provides recommended exhaust velocities for different boiler configurations and burner types.

Boiler Configuration Reference

Configuration	Velocity (m/s)	Velocity (ft/s)	Notes
Ducts at minimum load	< 4.0	< 13	Prevent excessive drafting
Stack at minimum load	< 5.0	< 16	Minimum load conditions
One-step burner (on - off)	5.0 - 8.0	16 - 26	Basic burner control
Two-step burner (high - low)	10 - 15	31 - 49	Improved modulation
Modulating burner	15 - 25	49 - 82	Full modulation capability
Soot prevention	3.0 - 4.0	9.8 - 13	Keep surface free from soot

Boiler Configuration	Min Velocity (m/s)	Max Velocity (m/s)	Min Velocity (ft/s)	Max Velocity (ft/s)
Ducts at minimum load	0 (no limit)	< 4.0	0 (no limit)	< 13
Stack at minimum load	0 (no limit)	< 5.0	0 (no limit)	< 16
One-step burner (on - off)	5.0	8.0	16	26
Two-step burner (high - low)	10	15	31	49
Modulating burner	15	25	49	82
Soot prevention (minimum)	3.0	4.0	9.8	13

Boiler Configuration

Min Velocity (m/s)

Max Velocity (m/s)

Min Velocity (ft/s)

Max Velocity (ft/s)

Ducts at minimum load

0 (no limit)

< 4.0

0 (no limit)

< 13

Stack at minimum load

0 (no limit)

< 5.0

0 (no limit)

< 16

One-step burner (on - off)

5.0

8.0

Two-step burner (high - low)

Modulating burner

Soot prevention (minimum)

3.0

4.0

9.8