grundfos pump (noisy)

[tangent1]

hi
I've got an odd problem in that my grundfos 15/50 central heating pump gets noisy but only when boiler switches off and its on overun. Is the pump on its way out or is there something else wrong?

Pete

 

[dfaz]

It could be that you have no Bypass valve on the system and when your motorised valve closes the pump isnt moving any water and cavitates producing noise.do you have 2 seperate zone valves or one three port valve.

 

[twgas]

is there a by-pass that is actually allowing water through?

 

[tangent1]

i have 2 motorised valves... i assume one for heating and one for hot water.... its not a problem that i've always had... its stated recently.

 

[tangent1]

oh... and stops making a noise if i turn it down to speed 1 during overun.... i once got rid of noise by momentarily turning it up to 3 and then back to 2. It came back though.

 

[twgas]

is there a by-pass that is actually allowing water through?

 

[tangent1]

i have seen a bypass and its open.... i can only asume its letting water through...

 

[muggles]

You could do better than assume, you could see if the pipework either side of the bypass is the same (hot) temperature

 

[tangent1]

ok... i'll check that in the morning and get back to you. thanks for your input.

 

[tangent1]

Sorry about the delay... so ... the bypass valve seems to be working ok... pipes hot either side...

 

[tangent1]

Thanks Guys....
I tweaked the bypass valve a little until the noise stopped. System still working fine so i guess its fixed. Why might it have started playing up in the first place?