Boiler or nearby piping emits a high-pitched whistling or howling noise

Safety: Noise issues can usually be investigated with the boiler running, but avoid hot surfaces.

• Check valves: Ensure all isolation and balancing valves near the Crown boiler are fully open unless specifically adjusted for balancing.
• Clean strainers: Isolate and clean any Y-strainers or inlet filters to remove debris.
• Adjust pump speed: If the circulator has multiple speeds, try lowering the speed to reduce noise and cavitation.
• Bleed air: Remove air from the system using vents on the boiler and radiators.