Problem: Ducts creak or bang when furnace cycles on and off.
Cause: Expansion and contraction of ducts.
Solutions: Operate the fan continuously to reduce expansion and contraction.
- Put resilient pads between ducts and supports as shown in Figures 26a and 26b.
Modify air ducts.
Figure 26a - Modification To Furnace Air Ducts To Correct Expansion & Contraction Noise
Figure 26b - Modification To Furnace Air Ducts In Wall Cavity To Correct For Expansion & Contraction Noise
- Add braces with resilient pads where panels flex. Identify locations by listening and/or touching.
- Fasten acoustic duct liner to the inner face of ducts to reduce vibration of duct walls and noise transmission along the duct.