Kickback in CH System

[gyeulet]

Last year, we had a new Potterton Suprima fitted, and the system converted from gravity to pressurised.

Since then we have had problems with a loud bang/kickback in either the flow or return whenever the room thermostat switched off (boiler shut down). The person who fitted suggested opening a gate valve (which is on either the flow or return - I can not recall) one whole turn. This is now done and the system now makes the noise when the thermostat switches in!!

Do I have to try and balance the system in some way?

The system is pressurised currently at 1.5 bar (Max allowable 3.0 bar). I see from my pump guide that there is a thing called "cavitation" - which can be cured by upping the system pressure - any ideas?

 

[oilman]

Don't increase the system pressure, unless you are in a 50ft high building. Search the forum for expansion vessels to learn about the pressure setting.

Is this gate valve placed between the flow and return? If so, it should be a differential bypass valve, and the gate valve is a bodge. To reduce the banging, try turning the pump speed down and see what happens.