grundfos pump rumbling what do i adjust

[help absolute novice]

Hi,

Total novice to this forum but just wondering if someone could help. I am self isolating at the moment as over 70.
My Grundfos pump ups 15-50x18 is rumbling a bit (not really loud). This noise appears even when the central heating is not on and the boiler is just on hot water. I know the pump is an obsolete model but it was purchased new sometime ago and only installed about 18 months. I have read somewhere that you can adjust the settings/speeds etc but i am unsure what i need to do. Hope the pictures help.
Many thanks.

 

[HERTS P&D]

Turn it down to number 2.

Andy

 

[MeldrewsMate]

The plain bearings in these pumps (and that one is at least 30 years old!) are lubricated by water. The large screw allows you to bleed air from the end bearing; loosen it 1/2 a turn and allow air to escape, close it when you see the first bit of water emerging. Then try turning the speed down.

 

[oldbuffer]

1. To adjust speed, use a screwdriver or similar to turn numbered white disc. Black numbers opposite body "arrow" cut out equate to pump speed, 1 being lowest. Best adjusted when not running but it doesn't make a big difference.
2. In my view unlikely to be anything to do with speed, unless there is s blockage somewhere in the system. Pump body should be mounted vertically or horizontally, NOT on a slope.
3. Most systems these days use the system to heat the central heating system and the heating coil inside the hot water cylinder. May be both at the same time.

 

[HERTS P&D]

Let us know if it makes any difference.

Andy