Humming central heating system

[delboybully]

A friend of mine asked me to pop round to their elderly parents as they have a wining noise coming from their central heating. The noise sounds like the neighbours are doing the hoovering (ie a quiet hum). It is coming from the airing cupboard. The pipes coming out of the pump are vibrating a liitle and the man of the house says the pipes never used to vibrate. My guess it its the pump but i dont want to be replacing the stuff unnecessary. They have had no work done in the house in recent months and the pump has been in for quite a few years

The system has a hot water cyclinder, a 3way valve and a pump with an old fashioned controller (manual type that has a timer that turns around- this make a noise but not the hum)

noise is driving them crazy to the point where sometimes they turn the heating of to get away from it

Any ideas?

 

[Morris40]

if you change the pump speed does the tone of the humming chnge ?

 

[delboybully]

I dont know, i only popped round to have a look, didnt think of that. Will go back tomorrow and try that

 

[delboybully]

I turn the pump down from 3 to 2 and the noise stopped! The pump still works. Its a Grunfos.

When i had a system similar to theirs my pump was on position 2, theirs was on 3. Both houses are terraced and similar sized

As long as the system still keeps the house warm will it be ok to leave the pump on 2.

 

[digdilem]

Yep, will be fine.

Could be they've turned down a radiator or something, or if they've not touched anything then sludge could be narrowing the pipes and creating more backpressure leading to the vibration (shouldn't do that at all really, but if the pipes aren't clipped and the pump not supported well, could explain why it wasn't making a noise before)