I don't think it will affect the a/c. It is possible that the exhaust could be slightly corrosive, and that may be an issue - it depends on whether it meets the offset requirements laid out in the manual. If it is far enough away, that effect should be diluted enough to not be an issue. But, it may be too close to either the corner or an operable window. The installation manual usually has some very specific requirements on this. The danger is that the boiler might be venting while you have a window open for whatever reason and you could be pushing CO into the house. The corner doesn't help, and the winds can do weird things around corners.