Coil Case Smaller Than Furnace Opening - HVAC - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Like Tree1Likes
  • 1 Post By yuri
Reply
 
Thread Tools Search this Thread
Display Modes
Old 02-16-2020, 06:15 AM   #1
Member
 
Join Date: Apr 2018
Posts: 33
Rewards Points: 66
Default

Coil Case Smaller Than Furnace Opening


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.
Attached Thumbnails
Coil Case Smaller Than Furnace Opening-86355800_507169133567284_4244115699259146240_n.jpg  
Adam Sinke is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 02-16-2020, 07:44 AM   #2
Hvac Pro
 
yuri's Avatar
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 22,470
Rewards Points: 246
Default

Re: Coil Case Smaller Than Furnace Opening


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.
Adam Sinke likes this.
__________________
"Cut it twice and it is still too short".
yuri is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 02-16-2020, 08:42 AM   #3
Member
 
Join Date: Nov 2014
Posts: 5,864
Rewards Points: 776
Default

Re: Coil Case Smaller Than Furnace Opening


Return the coil for the correct size. You ordered the wrong width.
roughneck is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 02-16-2020, 07:09 PM   #4
Member
 
Join Date: Apr 2018
Posts: 33
Rewards Points: 66
Default

Re: Coil Case Smaller Than Furnace Opening


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?
Adam Sinke is offline   Reply With Quote
Old 02-16-2020, 07:12 PM   #5
Member
 
Join Date: Nov 2014
Posts: 5,864
Rewards Points: 776
Default

Re: Coil Case Smaller Than Furnace Opening


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?
roughneck is online now   Reply With Quote
Old 02-16-2020, 07:42 PM   #6
Member
 
user_12345a's Avatar
 
Join Date: Nov 2014
Location: Canada
Posts: 12,481
Rewards Points: 120
Default

Re: Coil Case Smaller Than Furnace Opening


2 tons is very small to put paired with an 80k furnace - unless you're in winnipeg or something.
__________________
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
user_12345a is offline   Reply With Quote
Old 02-16-2020, 07:44 PM   #7
Member
 
Join Date: Apr 2018
Posts: 33
Rewards Points: 66
Default

Re: Coil Case Smaller Than Furnace Opening


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.
Adam Sinke is offline   Reply With Quote
Old 02-16-2020, 07:50 PM   #8
Member
 
Join Date: Nov 2014
Posts: 5,864
Rewards Points: 776
Default

Re: Coil Case Smaller Than Furnace Opening


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?
roughneck is online now   Reply With Quote
Old 02-16-2020, 08:01 PM   #9
Member
 
user_12345a's Avatar
 
Join Date: Nov 2014
Location: Canada
Posts: 12,481
Rewards Points: 120
Default

Re: Coil Case Smaller Than Furnace Opening


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/
__________________
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
user_12345a is offline   Reply With Quote
Old 02-16-2020, 08:06 PM   #10
Member
 
Join Date: Nov 2014
Posts: 5,864
Rewards Points: 776
Default

Re: Coil Case Smaller Than Furnace Opening


Where in the world is this old farmhouse located?
roughneck is online now   Reply With Quote
Old 02-16-2020, 08:14 PM   #11
Member
 
Join Date: Apr 2018
Posts: 33
Rewards Points: 66
Default

Re: Coil Case Smaller Than Furnace Opening


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.
Adam Sinke is offline   Reply With Quote
Old 02-16-2020, 08:16 PM   #12
Member
 
Join Date: Nov 2014
Posts: 5,864
Rewards Points: 776
Default

Re: Coil Case Smaller Than Furnace Opening


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.
roughneck is online now   Reply With Quote
Old 02-16-2020, 08:21 PM   #13
Member
 
user_12345a's Avatar
 
Join Date: Nov 2014
Location: Canada
Posts: 12,481
Rewards Points: 120
Default

Re: Coil Case Smaller Than Furnace Opening


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.
__________________
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
user_12345a is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Top of Page | View New Posts