3 Ton Coil with 2 ton condenser/compressor


  #1  
Old 09-16-19, 07:24 PM
D
Member
Thread Starter
Join Date: Jan 2009
Location: SE Texas
Posts: 39
Likes: 0
Received 2 Likes on 1 Post
3 Ton Coil with 2 ton condenser/compressor

My Coil is leaking. Had two estimates, but one guy wants to install a 3 ton coil in place of the 2 ton coil and says he can replace a piston(?) to make it work with a 2 ton system. He wants to do this as he says I can upgrade to a 3 ton unit when my 2 ton compressor conks out later on....
Is this even possible?
He is actually cheaper on the repair and won't charge any difference between the 2 and 3 ton coil.

I have never heard of this and can't find anything on the web.
 
  #2  
Old 09-16-19, 08:48 PM
R
Member
Join Date: Oct 2016
Posts: 2,416
Received 178 Likes on 164 Posts
Isn’t going to get expensive when you have to start redoing duct for a larger unit?
Mismatched sizes are common, no big deal. But you absolutely don’t want to start upsizing equipment for no reason.
 
  #3  
Old 09-16-19, 09:28 PM
D
Member
Thread Starter
Join Date: Jan 2009
Location: SE Texas
Posts: 39
Likes: 0
Received 2 Likes on 1 Post
It's cooling right at 1800 sq ft and both A/C guys suggested it wasn't big enough. We have a single story home that is rather large at 3560 sq ft. They have the systems split into a left and right side and the other side has a 3.5 ton unit.

They are just changing the coils with plenum box, the blower, ducts and vents will all remain the same.
 
  #4  
Old 09-16-19, 09:34 PM
R
Member
Join Date: Oct 2016
Posts: 2,416
Received 178 Likes on 164 Posts
Sizing isn’t done via square footage.
Bigger unit=bigger ducts. There’s more air that must be moved.
If they want to put in a bigger unit demand they prove it via an AHRI approved manual J calculation.
 
  #5  
Old 09-18-19, 04:25 AM
S
Member
Join Date: Jan 2017
Location: USA
Posts: 568
Likes: 0
Received 13 Likes on 10 Posts
My old Boss from the HVAC company I worked for in the late 1960's often used a larger coil in the air handler than the size matched for the condensing unit. We installed Lennox, York, and Bryant units and he said that this was a normal thing to do and said that he was supplied catalogs that showed this being acceptable. I was a newbie when I worked for him so I can't give an educated answer. He said that you could squeeze a little more capacity and humidity control out of the unit As I previously stated, I do not know if he was right but I do know that it was done.
 
  #6  
Old 09-26-19, 10:21 PM
user 10's Avatar
Member
Join Date: Mar 2004
Location: NA
Posts: 2,148
Received 50 Likes on 44 Posts
Coil tonnage ratings only apply to 13 SEER matchups.

It's common to have to use a higher nominal tonnage rated coil than condenser for a 14+ SEER system to get the rated efficiency and capacity.

Now, if your existing system is a 10-11 SEER (pre-2006), a new 2 ton nominal coil will already be much larger than what you have, and going up to a 3 ton/13seer rated coil, it will be grossly mismatched and the refrigerant pressures could be elevated.

Remember, the outdoor coil needs to be able to reject the heat collected by the evaporator. The higher seer units which use large indoor coils also have larger outdoor coils and the correct compressor for the setup so the system is balanced.

BTW increasing the size is not an upgrade - your ducts probably can't take the airflow and short cycles don't allow for much dehumidification.

Sizing is not done by square feet. If it's been cooling fine (running continuously in extremes is okay) you don't need a bigger unit, and if it hasn't been odds are there's another issue and it's not undersized.

Unfortunately, the residential hvac industry doesn't seem to attract the best of people; if you don't do your own research you can easily be screwed.
 
  #7  
Old 09-27-19, 10:39 AM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Likes: 0
Received 8 Likes on 8 Posts
Not the best thing to do with 410 systems. 22 was a bit more forgiving
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: