You need to adjust the lock shield valves so that there is a temp drop of about 11 degrees C across each radiator. You can either use clip on rad thermometers for this or an infra red thermometer or some peeps have been doing it so long they know the difference using their hand.
If you have TRVs remove the heads. Close down all LSVs and let system cool. Balance flow and return temps at boiler first - again approx 11 deg C drop using pump speed to regulate.
Starting with the first rad to get warm when the system fires up open up the LSV until you get the 11 deg difference between flow and return. Then move onto the next until you have done them all.
Your system is now balanced. Replace all TRV heads.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!