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Old 08-20-2009, 09:31 AM   #1
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acceptable to oversize coil


I am replacing condenser and coil, keeping my current furnace. I currently have a 4 ton unit , which is oversized for my house. One contractor wants to use a 4 ton coil with a 3.5 ton condenser, citing better airflow with my furnace if he installs the larger coil.
Any one know of any pros or cons to this?

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Old 08-20-2009, 11:05 AM   #2
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acceptable to oversize coil


Sounds like he has an extra 4-ton coil he is trying to unload.

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Old 08-20-2009, 12:33 PM   #3
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acceptable to oversize coil


I have a 3 ton condenser with a 4 ton coil and I haven't had any issues with it. I do live in a dry climate, so it's not an issue. If you live in a more humid area, I'd suggest not over sizing the coil.
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Old 08-20-2009, 01:36 PM   #4
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acceptable to oversize coil


Many manufacture matches need to have a larger coil to reach their SEER rating. Have him show you the ARI match for that system. This will tell you if it is a good match or not.
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Old 08-20-2009, 01:56 PM   #5
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Quote:
Originally Posted by hvac122 View Post
Many manufacture matches need to have a larger coil to reach their SEER rating. Have him show you the ARI match for that system. This will tell you if it is a good match or not.
I like this suggestion. Many indoor coils can server a range of tonnages such as 1/1.5-2, 2-3, 3-4; so it might be okay, just need to see the ARI numbers. If there is not match between the condenser and this coil tell him to get the right one. Also, condensers are typically matched to a few different indoor coil design variants that give slightly different performance. You want to get the most bang for your buck.
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Old 08-20-2009, 06:41 PM   #6
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Quote:
Originally Posted by pirateo View Post
I have a 3 ton condenser with a 4 ton coil and I haven't had any issues with it. I do live in a dry climate, so it's not an issue. If you live in a more humid area, I'd suggest not over sizing the coil.
Boy is that true!
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Old 08-20-2009, 06:44 PM   #7
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acceptable to oversize coil


if he over sizes that coil you won't get better airflow. The fin spacing is going to be tighter and you will lose volume. Your duct work may not handle it as well
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Old 08-21-2009, 10:32 PM   #8
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acceptable to oversize coil


It really just depends on the ARI coil match and the SEER rating that is trying to be achieved.

Some equipment requires 1/2 and sometimes 1 full ton upsize of the coil. But, is is not a standard rule of thumb that has any accuracy.

Our company has ARI matched coils that are ARI certified, and in some cases and ratings, upsizing is the norm. We also represent the "HE" ADP coils that are very short, and in almost every case the ARI match is an upsize of 1/2 ton up to 3.5 tons and 1 full ton at 4 ton. These are not recommendations that we make, but that of ARI.

Your contractor may be right. And then again, he may not.

List the models of outdoor unit and coil in question, and lst us see if we can help. You can also go to ari.org and check it out for yourself.

Good Luck
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Old 08-22-2009, 06:50 AM   #9
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Hey guys the ARI numbers are all well and and good. But one thing we are not considering is the size of the coil in comparison to the duct system.

Since it is an older unit being replaced it's got to be ten SEER or smaller. That means the available ducting might not have enough air flow to push thru a larger coil that is most likely wider, taller and restrictive.
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Old 09-03-2009, 09:27 AM   #10
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Sorry, I did not realize I had gotten further replies to this topic!
The coil I currently have is 4 ton, the entire system including furnace was replaced in Oct of 2000. The condenser @4 ton is oversized for the house, and the compresser is starting to go out, so I have been getting estimates on replacement of the a/c. Every contractor I contacted has agreed that the unit should be at least 3.5 ton, and one said it should be a 3 ton unit. At the current time, two have suggested a 4 ton coil paired with a 3.5 ton unit. I am trying to figure out my best option while my a/c system is still operating. I live on the very hot and humid Gulf coast, and a/c is a definite necessity!
Thanks for any opinions and suggestions.
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Old 09-03-2009, 10:25 AM   #11
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Best to have a load calc done, to find out what size A/C you really need.

The closer your unit is sized to the load of your home. The better it will remove moisture from the home, and keep the humidity in check.

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