Found the Canadian version of my water heater manual online. Funny, if you look at page 13 and 14 it even shows which elbow to use. The US version has no such page!
Note the first graphic on page 14. Why can they install this heater with less than 12″ of vertical pipe in Canada but not in the US??
I will try a 90 long sweep tonight when I get home. I tried a short 90 last night and got same error lock out code, which according to this manual is not be used! GRRRRR.