replacing ThermoPride OIL furnace with NG, have some questions

[dannemand]

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.

thanks!

[gasguy]

You need to have a 'manual j' or heat loss calculation done on the house to properly size the new furnace. You input all the sizes & details of your house (design temperature, orientation, windows, insulation, leakage rate, etc.) into the program and it calculates the rate of heat loss. This allows proper sizing of the furnace.

[dandyme]

was there a load calculation done before the 85kbtu T-pride was installed??

have you made any upgrades to the structure since then??

[dannemand]

I am the second owner of the house, I can only assume they did a calc. The house has not changed other than I am residing and wrapping it. It is a mid 80s split level.