Venting problem

John_133

This is a follow up to original thread "Help...", from yesterday.

First, thanks to Freak and Mr. O'Connor for their responses.

My latest question is:

If one boiler is to be vented through the existing chimney flue and the second one is to be vented direct through the wall, does anyone know the code for min/max distances of the vent to the wall? I've been told there is a min 18 inch clearance from the ground but don't know where to find the code for distance to the wall.

The scenario, both boilers are against a wall that has a crawl space behind it. Ideally, I'd like to vent through the crawl space to the exterior wall. This would put the outlet on the side of the house. Otherwise, it will need to go to the front of the house -- wife won't like that idea. Thanks in advance.
John