[Hunda]

The boiler seems to start normally. First the auto damper opens, the pump starts, the electronic ignition is heard and then the burners light. At that point it makes a very high pitched harmonic noise. It sounds like a motor with a bad bearing. I have laid on my back trying to pinpoint the noise, and it is loudest near the left burner.

[Grady White]

Sometimes we encounter burner doing this but quiet down as they warm. Did you have the boiler professionally installed? If so, call the installer back. It could be a gas pressure issue, bad burner, defective orifice or any of numerous other problems. The installer should take care of it at no charge.

[Hunda]

After I read answer #1 I called a gas company. I had used a 1/2" flexible hose and that did not let enough gas pressure. They rerouted some pipe and used a 3/4" flexible hose and it worked perfectly. The problem was low gas pressure to the boiler.

[Grady White]

Often flex lines have to be upsized at least one size beyond what one would normally use with pipe. Glad it was that simple.