i recently changed expansion vessell and heat exchanger on vokera 24 comi, the heating side is working fine but heating side is,nt. when you turn on hot water its fine but when u stop running hotwater u get a loud gurggling sound and boiler shuts down??
After you changed the heat exchanger did you remember to open the isolating taps under the boiler so the water can circulate through the radiators, ?, did you bleed the radiators?.