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Discussion Starter #1
I've ordered a furnace and evaporator coil case (with the coil) off of Amazon. An 80,000 BTU furnace and a 2 ton coil. They are both Goodman brand and when I set the coil on top of the furnace I found that it was smaller. I have three options in order of preference. 1: Retrofit the coil case to fit on top of the furnace. Add a 2-inch wide piece of 18 gauge metal on both back and front of the case to expand the size. 2: place a reducer on top of the furnace. 3: return the unit and reorder another one that is the correct size. Any suggestion about which course I should take would be very helpful.
 

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Return it and get the proper one.

If you have a spot/area with poor airflow it will ruin the heat exchanger below it.

The part of the tube heat exchanger you see now will run too hot and fail prematurely.
 

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Discussion Starter #4
Okay, so I got the wrong one. I return it as suggested. Now I need to buy the right one. Does the coil's physical size have to match the furnace or does the "rating" size have to match the furnace? Example: can you put any one of the 1.5, 2.5 or 3 ton coils on an 80,000 BTU furnace? Or if you have an 80,000 BTU furnace do you have to go with a specific ton size coil? Example my 2 ton coil does not fit my 80,000 BTU furnace. Can I get a 2 ton coil that would be the correct physical size for this furnace?
 

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Cased coils normally come in different widths.
The blower in the furnace will have a rating related to the air conditioner.
You should be getting an AHRI matched system. What’s your system match number?
Going beyond your original question, 80,000 BTUs is a rather large furnace. You must be planning on heating a large area. What were you heat loss numbers when you did your calculations?
 

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2 tons is very small to put paired with an 80k furnace - unless you're in winnipeg or something.
 

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Discussion Starter #7
I am a layman who thought he could pull it off on his own. Now, it'll eventually work out but these are the hiccups that come with trying to do it on your own.

I got the 80,000 BTU furnace on the suggestion of a family friend who does HVAC. I am heating a 2 story, 1938, 1800 sq ft house with a finished basement.

I then had a 2 ton goodman compressor given to me. I figured I had to match the coil to the compressor so I went a two ton coil in the case and I figured because they were all the same brand the case would fit the furnace.
 

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I would stop and think before continuing with the installation.
You’ll need an accurate load calculation to determine size. The air conditioner could be too small or too big.
Same for the furnace.
The furnace will need to move the correct amount of air for the air conditioner. Too much or too little will cause all sorts of problems.
The equipment should be matched via an AHRI match number. Not doing so will not guarantee size or efficiency numbers.
At the moment your quite a long ways off the mark for what needs to happen to get a system that runs correctly.
How old is this unit you were given? What refrigerant?
 

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Most 3 ton drive furnaces can be slowed down enough for a 1.5 or 2 ton.

That old house of yours may not have large enough air ducts for the 80k.

Possible you need 80 if the house isn't well insulated and also possible 2 tons is the right size for cooling.

But without the calculations, you're guessing.

you can do your own whole house load calc for free here - https://www.loadcalc.net/
 

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Discussion Starter #11
I am in Northern Indiana. I've installed 5 8x5 foot windows and the main floor is like a fishbowl. I am installing all new ductwork because it was on a boiler without A/C when I bought it. The house is down to the studs right now and I can put in whatever size duct I need.

The unit I was given was 3 months old. The folks bought it, moved to a larger house and found that 2 tons wasn't enough for their new house.
 

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How are you laying out the duct?
Should be done with manual D with a room by room manual J.
Very, very important the duct is the proper size.
Do your own load calculation with the link above and post the results.
 

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Hot water heat can be more comfortable than forced air* - why not keep it and have a separate system for cooling? assuming you haven't removed the system yet.

*Unless you get properly sized 2-stage or modulating furnace.

The site i linked to is for whole house only and should only be a starting point.
 
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