I've been reading this forum for a few months while I was scoping out my options for replacing a Ye Olde boiler from an 1890's New England cottage. Finally decided on a Buderus GB142.
I was sized for a GB142-24 by the one contractor who really seemed comfortable with these units. So, I went with him and today's the install day. Unit's on the wall & I notice that the badge reads "GB142-45", which is two sizes up. Turns out the supply house screwed up & I get to keep the 45.
The contractor assures me that the AFUE will not be affected, but I've always heard that these GB units run more efficiently if they're slightly underscaled. Any opinions? Should I just be happy?