I was wondering about that too, but i think most of the concern is with the Quietside oil boilers. This unit has a bare minimum of adjustments for the gas supply. But i am going to have the guys who maintain my AC unit check it when they're here. So far it's running flawlessly with a 152 degree max. temp.
Don't be too impressed with my solder skills, i cheated a bit by doing a lot of the assembly at the bench (especially the brass fittings) so i had a min. of in-place joints that cause you to hold your mouth just right and pray a lot. ;}
Plus, that whole manifold will rotate out and away from the wall so you can get to the back of a joint easily. I get impressed by the pros i learned from who can stand on their head, on the top rung of a wobbly ladder and still make a perfect joint on a 2" tee, 3 pipes inside a maze of copper.