Pulsing Noise from Grundfos Alpha+ pump

[slimsoul]

Hi,

I have a Grundfos alpha+ 15/50 pump which is making a pulsing noise intermittently when in the variable speed setting (which is the setting it was set at when i bought the house, and not making any noise up until last year) it runs for about a minute smoothly then starts pulsing annoyingly for a couple of minutes, i have tried alternating C/H and H/W and it pulses no matter what is using the pump. The system is 4 years old.

Just by trying a few things and switching the pump to the opposite settings of 1 2 & 3 of which i set it at 2, i found the pulsing to stop and pump to start flowing smoothly again.

I recently bought a new pump and replaced the one that was there but i get the same problem, so i guess its not the pump?

Am I causing any damge to my system by leaving my pump on this setting? I have noticed a juddering noise coming from the motorised valve that goes into my tank when i use the no.2 setting.

Sorry if any of this is confusing there is a pic of the pump and valves in my album if it helps

thanks

 

[clearhead]

have you got an automatic bypass valve(or manual bypass btween your pump and motorized valves
is your pump running when valves have closed(called pump over run)
have you picture of more pipe work valves etc

 

[slimsoul]

Hi, many thanks for the reply.

There is no bypass valve between pump and valves, it tees after the pump to CH valve and HW valve.
The pump usually stops on demand, it has continued to run twice i think in the last year, when I have manually turned the lever on the CH valve to stop it?

I will try to get some pics of the setup this evening

 

[slimsoul]

More pics added

 

[clearhead]

hi - personally i think you need a system bypass which goes between pump & Valves-this is to take excess heat away from your boiler-and to allow pressure relief from positive side of pump
maybe the bearings in the pump are getting worn
are you getting air into the pump-are you getting air into system-do you have to bleed radiators reguarly

it might pay to give grundfos a call they are really helpful