Boiler central heating systems have a number of advantages over furnaces, one of which is how little noise they make while functioning. Even the most powerful gas-fired boiler makes significantly less noise than the blower fans of a ducted furnace system. If your boiler system starts to make loud noises, it could be a sign of mechanical problems.
The circulator pump is one of the most important components of any boiler central heating system. It circulates hot liquid through your home's radiators to provide heating, and drains cooled liquid away from the radiators and back to the boiler's heating chamber. If it starts making loud, unusual noises, it may be suffering from a problem known as cavitation.
What Causes Cavitation In Boiler Circulator Pumps?
Circulator pumps contain impellers, which pressurize the liquids that pass through them and force them into the radiators. As a consequence, the liquid entering the circulator pump through the pump's inlet valve has a much lower pressure than the liquid exiting the pump through the outlet valve, creating a significant pressure differential.
This difference in liquid pressure is a normal consequence of residential boiler design and ordinarily doesn't cause any problems. However, if the pressure of the liquid entering the pump is abnormally low, the massive difference between inlet and outlet pressure causes some of the liquid inside the pump to vaporize. As it vaporizes, it creates thousands of tiny bubbles of air and water vapor.
The pressure of the liquid entering the circulator pump can drop for a number of reasons. If your boiler's heating chamber or pipes are clogged with scale or sediment, liquid will reach the pump too slowly, causing pressure loss. There may also be a hidden liquid causing liquid pressure to drop across the entire system.
Pressure loss can also occur if you have recently bled a radiator to remove trapped air pockets. These air pockets reduce the heating efficiency of your radiators, but removing too much air from the system can cause systemwide loss of liquid pressure.
Why Does Cavitation Make Circulator Pumps Noisy?
As the impeller rotates inside a cavitating pump, the bubbles of air and vapor explode as they impact the impeller blades, creating thousands of tiny shockwaves. These shockwaves create a loud rattling or rumbling noise, and it may sound like your circulator pump is full of gravel.
However, cavitation doesn't just cause noise. The vapor bubbles also create a lot of heat when they explode, which can seriously damage the impeller, impeller housing, and other important parts of the circulator pump. Running a cavitating circulator pump for too long can cause catastrophic damage.
What Should You Do About A Cavitating Circulator Pump?
If your residential boiler's circulator pump is making a lot of noise, you should deactivate the boiler as quickly as possible, before calling in a residential boiler repair service to inspect the circulator pump. These professional services can safely dismantle the pump to check for cavitation damage, and repair or replace any damaged components.
Your boiler repair service can also rectify the cause of the cavitation. They can remove sediment deposits, find and repair any leaks in the system, and inject air into the system if excessive radiator bleeding has caused the cavitation to occur.