This is from Potterton Kingfisher II (CF60, 80 & 100 LPG) user's guide - the graduations from min. to max. correspond approximately to a temperature range of 55 to 82 degrees C for water temperature as it leaves the boiler. The guide notes that higher settings to be used when central heating on but can mean water in domestic hot water tank scalding hot unless this is independently controlled!
Hope this helps.
SLugg, October 2012
