We had a new Grundfos circulation pump installed in our house at the start of this season. Over the last few weeks it's been humming pretty loudly, especially at night, and there's a slight vibration you can feel on the pipes. Never happened before. Could it be installed wrong or is there something that needs adjusting?
Air in the system is the most common cause of this noise, especially if the pump is new and the system was recently filled. Check if your pump has an air release valve (usually on top) and try unscrewing it a half turn until water comes out without bubbles. If that doesn't help, the humming could be from incorrect installation - the pump should be positioned horizontally, not at an angle, and it's important that the shaft rotates smoothly.
Also check if the rotation speed is set correctly on the pump body (there are usually three settings) - it might be running at maximum power when your heating system actually needs lower speed. If the noise persists after that, call the technician who installed the system - there could be a defect or a mounting problem.
Log into answer.
