top pressure up to 1.5 on pressure guage do this when system is cold to get a true reading switch on heating and watch guage if it goes up to 3 barr or over it could be one of three things ,expanssion vessel, filling loop letting by or plate heatexchanger if plate heatexchangers been changed that elimenates that try setting correct pressure again to 1.5 then if you can disconect filling loop and see if it leaks if not it will proberbly be the expanssion vessel if you like call me and il talk you through it 07923258885 between 9 and 4
john
March 2010