Sounds like water hammer after pump over run

[Sammyt]

Hi

Ive got a problem I've not come across before.
when heating call to the boiler switches off the circulating pump runs as it should for aprox 3 minutes, the second the pump stops there is a loud bang or 2 from the airing cupboard/loft.
Gravity system, BRitish gas install around 3 years ago but person only moved in recently.

thanks

 

[01ST13795]

2 port valves or 3 port? Bypass fitted?

 

[Sammyt]

2 port valves or 3 port? Bypass fitted?

3port working fine
auto bypass also seems to be working fine, set down to 0.1 bar to check it's letting by

 

[Sammyt]

Any one got any ideas?

 

[gasmanrob]

Thermal shock? Three port valve slamming shut? I had the latter last week the three port slammed shut so hard it could be heard all over the house valve was three weeks old

 

[Sammyt]

Thermal shock? Three port valve slamming shut? I had the latter last week the three port slammed shut so hard it could be heard all over the house valve was three weeks old

Doesn't the 3port adjust as soon as the call for heat stops, where's the pump continues to run for a couple of minutes?

 

[kimbo]

This happens quite a lot with 3 port valves. One of the reasons I always fit s plans

 

[Sammyt]

This happens quite a lot with 3 port valves. One of the reasons I always fit s plans

How would a Y plan make this noises over S plan?

 

[kimbo]

Dont know but mainly happens with y plans never had it happen with s plan

 

[Sammyt]

Dont know but mainly happens with y plans never had it happen with s plan

Ok thanks I'll try the valve