Is the reason that the nozzles need to be replaced on older burners because most older burners have a hard combustion chamber?
I bought the kid a KM800 off Ebay after getting a pretty high quote from a furnace service company. I asked them what sort of instrument they used and he said a smoke spot test. How long do the oxygen sensors last? And is this dependent on how often they are used?
Inquiring minds want to know.