Hello everyone, I am new here and this is my first post.

I have a 2800sqft house that is heated by a ThermoPride Oil OL5-85 furnace, and a matching ThermoPride WC20 wood/coal furnace which I do use. I am looking to replace the oil furnace with NG and keep the wood furnace.

The oil furnace is rated at 85000 BTU using no2 oil with a .75 nozzle at 80% efficiency, this is right out of the owners manual, as seen here: http://www.thermopride.com/pdf/oilfiredfurnace.pdf

It currently has a .65 nozzle installed.

I'll start with the first question and let the discussion go from there.

How do I figure out what size NG furnace to install, I am looking at a 95% effecient model now. The oil furnace seemed to perform well, in fact I am using it now, taking a break from chucking wood, and using up my oil reserves so I can remove the tank.