The old Mikey would argue all day and into next week about that.you don't need blazing heat....but I agree that about 210 is the sweet spot for making your life a bit easier cleaning........
If the transformer goes, your ignition source goes. now you have kero shooting through your coil and not being burned. Only happened once to me and fortunately I was home at the time. I grabbed the one in my basement off of an old oil furnace. Its still on there today, but as a back up sitting in my shop.The kero units can have an ignitor go out like a blown light bulb.
Never at a great time.
So just a little above lukewarm.Judging by the video, 122 degrees is the sweet spot for barely soiled residential.
What is the best temp for cleaning carpets.
If your running 210 at the machine, what temp is it after 150ft of hose? Also is there a device to check water temp at the wand?