Reillo recommends,
Gap between electrode flats of: 4.0mm (+/- 0.3mm)
Gap from from of nozzel to electrode: 2 - 2.5mm
Be careful, make sure to isolate electricity & oil before messing with these, you could get a bad shock from electrodes....
My advise would be get you service engineer to set this up, as you may also need to do a flue gas & smoke test, set your oil pressure and air intake.
Remember, just because it doesnt smoke, it can still generate carbon-monoxide that kills in minute ammounts!!!
T, January 2008