Grundfos pump rattle

[Kurt]

Hi . I replaced my wilo smart heating pump today as it had developed a problem with surging . I fitted a grundfos alpha2L 15-60. The pump is preset to pp2 and is recommended for most systems . On first start up their was a chattering from the pump which I first thought was air . The noise eventually went but comes and goes intermittently . The only way I can stop the noise perm is to turn it down to pp1 but don't want to cause other problems by doing this . I have googled the problem and sorry know nothing about flow rates etc which all the info refers to . I have an open vented system with 12 rads and a new boiler fitted in Nov 2015 . It also has a manual bypass . Any advice would be appreciated

 

[thompsonbrown]

Sounds like its still a bit of trapped air in the system, failing that is all your pipe-work clipped.

 

[Kurt]

Everything is clipped in as far as I can see . The pump is suppose to be self bleed . One I have noticed is that the last rad on the line takes a long time to get hot with the pump on the lower setting .

 

[Ric2013]

I once had a gate valve next to a pump rattle. The gate valve was just off fully open. Turning the valve to 100% open (I usually back valves off a smidgen) solved the problem. Could this be you?

 

[Kurt]

Could be the valves were a nightmare , seized solid . I'll try moving the and see if the rattle stops

 

[lame plumber]

if they turn nice and easy now, almost spin on their own, you may well have a sheared valve stem.

 

[Kurt]

I have moved both the valves back and forward to re seat them . They don't feel that loose that the shaft is broken . I have also turned the boiler down a bit as the rads are roasting with this new pump . It's been on for half hour now and no noise , fingers crossed , will keep you posted

 

[Kurt]

Unfortunately I still have a slight int rattle from the pump . I have ruled out the valve as you can hear the noise from the pump with a screwdriver . Is it going to cause any damage to the heating system or boiler if I leave the pump setting on pp1