We are going to replace our two 19 year old 1 stage Heil gas furnaces. We live in Charlotte, NC so we don't have extremely cold winters. Our first furnace is in our crawl space and heats our 2400 sq ft first floor, and our second furnace is in the attic and heats our 1800 sq ft second floor.
We have had heat equalization issues both upstairs and downstairs with our 1 stage furnaces. Our downstairs thermostat is in the front entry hallway. We often need to close the doors that let air circulate between the front and back areas of our first floor. As a result the back of the first floor where we spend most of our time tends to get less heat than does the front. It's especially cold in our family room which is the furthest distance from the furnace. We have thought about adding a new zone to the back of the first floor so that we can better control the heat going to this area, but we have been told that this solution is expensive and not necessary. We have been told that a better solution is to replace the 1 stage gas furnace with either a Trane XL 90 regular 2 stage gas furnace or a Trane XV 90 2 stage variable speed gas furnace. Will either or both of these 2 stage furnaces let us equalize the heat between the front and the back of the first floor? Will the 2 stage variable speed furnace do a significantly better job of equalizing the heat than the regular 2 stage furnace? We know that the 2 stage variable speed furnace is more expensive, but our contractor is willing to include a whole house humidifier with the variable speed furnace at no extra cost while we will have to pay extra for the humidifier if we choose the regular 2 stage furnace.
On our second floor, the master bedroom has more ducts than do the other three bedrooms. The thermostat is in the hallway and when all of the bedroom doors are shut, the master bedroom gets uncomfortably warm before the other bedrooms become comfortable. Again we have been told that a regular 2 stage or a 2 stage variable furnace will help solve this problem. We have also been told that we may only need an 80% AFUE furnace upstairs instead of the 90% AFUE furnace that is recommended for the first floor. Is the 80% AFUE furnace OK for upstairs? Again will the 2 stage variable speed furnace do a significantly better job of equalizing the heat than the regular 2 stage furnace? The whole house humidifier is only included on the first floor furnace so we will get no price break if we put a 2 stage variable speed furnace upstairs.
2 stage VS will help, but won't be a cure all.
The problem is your duct system, not your furnaces.
Zoning may be expensive, but might be the solution to your family room problem. If the contractor is trying to talk you out of it, he doesn't know how to do it right.
Get more estimates, you don't get a humidifier for free, its in the price.
Leave the two stage out of the equation.
Do a balancing on the system properly with what you have got NOW...before you alter/change the furnace just to see what gives and is possible now with what you have.
If you replace your furnaces replace with heil and use the money you saved from buying a trane towards fixing your ductwork.
As a hvac business owner and a heil dealer in chicago I would go with a two stage,but our winter temps are as bad as greenbay this year. GO BEARS
Check out http://www.heil-hvac.com/ and find a dealer in your area but remember that your problem is your duct lay out and not your furnaces.
If and when you replace that attic furnace make sure they install it over a emergency drain pan and on vibration pads.
Wait for robo, he will guide you.
[Edited by jultzya on 10-30-2005 at 11:52 PM]