No, it is not normal for a hot water baseboard heating system to make loud grating, bubbling noises when the heat turns on. Typically, a well-maintained hot water baseboard heating system operates quietly without any excessive noise. Loud grating or bubbling noises can indicate a problem with the system that should be addressed.
Possible causes for these noises could include air trapped in the system, a malfunctioning pump, water flow issues, or a buildup of mineral deposits in the pipes or radiators. It is advisable to have a professional HVAC technician inspect the system to identify and resolve the specific issue causing the noise.
Regular maintenance and bleeding the system to remove trapped air can help prevent such issues from occurring. If you notice unusual noises or any other problems with your heating system, it's best to have a qualified professional assess and address the situation to ensure the system operates safely and efficiently.