W
wilhelm
velaire 20kw, inter 109 burner, there is a low level humming when the burner fires up , you can hear it outside from the flue which goes through roof,(bungalow) as well as inside. new pump, motor &fan, you can also hear it at tank 80ft away if you hold screwdriver to filter. is it possible the pump is straining to pull from that distance, i noticed there is a mixture of 10/15mm pipework in supply...........your views greatly appreciated cos its doing my head in...........cheers