Furnace is very noisy during operation, with humming, rattling, or vibration transmitted through the house

Safety first: Turn off power before tightening or adjusting mechanical parts.

• Check mounting: Ensure the furnace is securely fixed to the wall or floor and that all mounting brackets are tight.
• Tighten panels: Tighten screws on the front and side panels. Add foam strips where metal parts vibrate against each other.
• Bleed air: Air in the pump can cause cavitation noise. Bleed the pump and system as per the manual.
• Inspect fan: Spin the combustion fan by hand (power off). If it feels rough or wobbly, the fan assembly may need replacement.

Warning: Do not operate the furnace with the combustion chamber cover removed; this can cause unsafe combustion.