Sizing Input - PLEASE HELP

[Detox]

I really need some furnace sizing help so I can make a decision.

Current Setup:
1920's three storey semidetatched house in Toronto, double brick almost no insulation.
Approximately 2200sqft (including basement)
20year old Lennox G8 furnace 120,000BTU (90,000 BTU @75% eff)


I've performed two separate heat loss calculations (one using HVAC Calc) and the other using a simplified example of the Canadian CSA F280.

HVAC Calculation Report = 105,000BTU
F280 Simplified Calc = 80,000BTU (takes into account 40% oversize)

I am looking at the Carrier Infinity 96% HEF. The problem is it comes in an 80,000BTU and an 100,000BTU version. And I don't know which one I should choose.

My understanding the way the 2-stage variable speed Carrier Infinity works means a 100,000BTU would not be a problem even if it might be a little to big, due to the variable speed.

Some input would be greatly appreciated so I can pick a model and move on. I plan to pair this with a 2-TON condenser.

Thanks

Detox

[jwiehagen76]

Have you thought about sealing up the building a little better? Then you can recalculate and most likely reduce the load. Rarely do i ever have a load of 100k or greater.

[beenthere]

If it says you need 80,000BTUs output, get the 100,000BTU input unit.

[amd]

Insulate and draftproof where practical/economical.

Today's high efficiency furnaces move much more air than your old G8 (rated temp rise 70-100F if I remember correctly; new unit might have a rated rise of 30-60F); the existing ductwork might have to be upgraded*.

[DanW13]

I thought I heard Carrier is going to stop making the 2 stage furnace ? Though parts should be plentiful for years to come. I think the Carrier Infinity 96 ICS comes in 60K-120K BTU gives you nice comfort control, fully communicating and for a couple of bucks more might be a better choice.

As for your home I second the motion of tightening up your home, insulate, upgrade the windows and throw some R-49 or better in the attic can lower your heat load by 15K-20K BTU's and would be money well spent and give you many years of pay back. Based on how bad the house is leakage wise a couple of weekends if your able and willing can net you alot of money.

you also have to look at the fact of how long your planning on living in this house will determine what your willing to put into the home, but what you put in you will get returned either in monthly savings, or when it's time to sell.