Did the other contractors take into consideration the finished attic? Is the roof adequately insulated?

If the heat calculation is correct, and you are presented with a copy, then it would be correct to have a 5 ton air conditioner.

Most homes built around 20 years ago had oversized furnaces and undersized ductwork. If your current furnace is on the loud side, then a larger a/c will cause your indoor unit to be much louder.

Also, under such a situation, the furnace unit would work harder due to increased static pressure and would probably enjoy a shorter life. For the sake of your attic, the rest of your house may be muggy due to running short a/c cycles (poor humidity removal), which could also negative affect the lifespan of the outdoor unit.

Did the contractor discuss the status of your duct system, and any modifications?

Also, an oversized furnace such as proposed would probably run almost exclusively in first stage. If you do go this route, insist on a 2 stage thermostat.

V

It would be a 5 ton furnace but just 4 ton condensor per the quote (model #'s are listed in original post)
Only 1 other contractor considered the attic space and he was thinking i only needed a 3.5 ton furnace, but when i told him about the attic space that is finished, he said would need at least a 4 ton. I am also have the panel replaced for the 2 zones i have and getting American standard thermostats- 600 family programable ones.

I think the ductwork is in good shape. home was custombuilt and all top of the line equipment insulation was put into the home.

What A/C are you getting (size)? Model #?

I don't see how having a 5 ton blower would necessarily help since it's still going to be set up for 4 tons of airflow/approx. 1600 cfm. The 5 ton furnace has a 1 H.P. motor;, the 4 ton has a 3/4 H.P.

Even the 4 ton furnace set up for 1600 cfm (your A/C) still won't be running at its max setting. Ask the dealer what his reasoning is exactly.

This is the condensor in the quote:

american Standard 4 TON, 14 SEER CONDENSER WITH THE R410A
REFRIGERANT MDL# 4A7A4048A1000A

First, if the duct system isn't set up for 2000 CFM, getting the bigger blower won't help. Also, unless you are in a very dry climate, moving 2000 CFM through a 4 ton system can make for higher humidity.

Personally I'd plan on staying with the window shaker. I don't think anything you can do will keep the attic as comfy as a lower floor since heat rises and the cool air falls. Also if furnace is in the basement, hard to push enough air up 3 floors.

I'd get the properly sized furnace. Make sure you get a nice 2 stage thermostat.

Agree with baldloonie, and also the 120k furnace will probably have to move more air yet, and if your ductwork can't handle it, it's a no go.

I really dont know what my ductwork is set up for and have no idea how to check. There are a bunch of numbers on the ducts i can see in the basement, but dont know if that means anything.

My goal is not to get the 3rd floor as comfy as rest of house, just did not want it to be an oven.

so it seems i should just request the 4 ton furnace if i go with this quote. am also going to make sure the thermostat is set for 2 stages.

Other posts here provided good advice.

Viewing the charts I put on the linked page below might be helpful.

Lower Air Infiltration & do what is essential for optimal ductwork & Airflow performance. - udarrell

Here is a link that might be useful: Ductwork Sizing & More

Update
Well i decided to go with the 5 ton blower on the furnace hoping it would help in cooling my 3rd floor space.

As far as the heat of my new system, could not be happier. This system is QUIET compared to what i had. Never hear it come on from the first or 2nd floor of house like i used to with the Pulse furnace we had. The house does not get overheated when system comes on, the heat is very evenly moved throughout the house. The old system would just blast max heat and would get so hot in the house.

Just started turning the AC on more the last few days and it is also working great. The condensor outside is super quiet, do not even hear it go on; used to be able to hear the old condensor all the time from inside the house. Also the cold air is getting to the 3rd floor and keeping it cool! It also seems i dont have to set the thermostat as low. the house is very comfortable set to 73-74 degrees. Last summer had to keep it on 70 to get comfortable in summer. Have not hit any 90 degree days yet so that may change. But right now, very glad with my decision to go with the AS 95% VS unit i noted in my first post. I also got the 10 year P&L warranty for that piece of mind coverage.

it’s been a while, but wondering how your system is doing today?

13 years later? It could be time to replace the replacement.

Let old threads rest in peace.