If you have a cooker and a gas fire at the property and your supply pipe is longer than approx 6Mtrs excluding bends in 22mm it is too small for this boiler to work properly. The boiler takes 4.4M3/h at max working pressure so a min 28mm pipe over more than approx 6mtrs would be required. You need a minimum of 18mbar pressure with the burner on full regards chrisey