Hi all, i have a standard CH system using a potterton nettaheat boiler, hot water tank in upstairs linen cupboard and water tanks in loft.we had the circulation pump replaced recently due to the boiler overheat stat cutting out, that all ok now but now we get a load howling scream from the pump occasionally. i turned it down to 2 from 3 but still makes the noise, usually a couple of times a day.the pump is a grunfoss situated next to the hot tank in the airing cupboard. Do you think i have air in the system causing the pump to run dry?
Leon
Leon