I have noticed that often when the circulator shuts down a whistling noise is heard for a moment. Can someone comment on what is causing this to happen?
Recently, a baseboard radiator heater was replaced and I did attempt to bleed the series loop at the boiler. Could this whistle be an indication that there are air pockets remaining in the closed loop? Prior to the radiator replacement I do not recall ever hearing the whistling sound.
Thanks
de ~ Vince ~ Long Island in New York