Apart from cleaning the H/X what else is there to do, apart from the above?
The most important is setting the max/min gas pressures.
Amazingly only about 25% of gas people seem to know how to set those. I had a call from someone today who was asking as the BP was high.
Yesterday I went to a problem with the burner cutting out on DHW and the min was 4.5 instead of 1.5 !
Tony