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  1. #1
    Join Date
    Jul 2012
    Posts
    18

    Does anyone still use over size Air Handler?

    Some years ago, it was not unusual to see an over sized Air Handler. Like a 2 !/2 condensing unit paired with a 3 ton air handler. These days systems are designed to be highly efficient. So I'm wondering if there is still an advantage to an over size air handler, or if it will just cause problems.

    Case in point, I'm working on some condo's that have height restrictions. I found the Goodman AWUF wall mount units that will work. The problem is that they are only 13 SEER. The owner wants to replace with higher efficiency. I plan to add a TXV which will make 14 seer, but if I over size the A/H by 1/2 ton, will that help? The condos are currently running 2 1/2 ton which is about right.

    Thanks guys,
    Scott

  2. #2
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,378
    If the customer is concerned about power bills then downsizing to a 2 ton would have the same effect as adding 1 SEER point due to longer run cycles. The potential issue is that the unit may not be able to keep up on the afternoons that exceed design conditions. I always say fix the house (reduce heat gain) and use the smallest equipment that will do the job.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,317
    Don't ask us, ask Goodman. Do they AHRI rate their 2.5 ton with the 36 AH? If so, fine. Or if 2.5 is about right, see just how about that is. 54's suggestion of a 2 ton has merit. Lower air flow, quieter. Longer run times, more efficient & better humidity control which you can lose with the oversized AH.

  4. #4
    Join Date
    Jul 2012
    Posts
    18
    I appreciate your ideas. I had not even considered down sizing.

    In that area, they figure about one ton per 500 sqft. This condo is 1200 sqft, so 2 1/2 ton is about right. The condos on the first floor cool down and shutoff on a hot day, but the top floors condos, which this one is, do struggle some. Because of that, I don't think down sizing is an option.

    I have tried to ask Goodman about mixing a 16 seer condensing unit with a 14 seer air handler. They always cut me off short telling me it won't work. The thing of it is that I am assuming the air handler will be about 14 seer with an added TXV. I guess I need to stop suggesting that and make them figure it out. The thing of it is, I always thought that the seer rating of a system came mainly from the condensing unit's rating.

    Can anyone recommend an air handler that would be less than 42". I have found some that are 42 1/2" but they need to have a filter base added, which makes them too tall.

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,378
    One ton per 500sqft may be appropriate for old homes, but newer homes can typically do fine with much less. Newer homes can get a 20 degree difference (75 inside when it's 95 outside) with as little as 1 ton per 1,000 sq ft. In order to get that the home must be well insulated and the unit must be installed absolutely correct.

    Something else to consider is your ductwork. Fixing/insulating ductwork will got a LOT further in reducing your power bills than increasing SEER. But then we're back to fixing the house and going with a smaller unit to save energy instead of increasing SEER. The idea is stop the heat from getting inside, then deal with what does get in.

    If it were me I'd do the 2 ton and if it isn't quite cool enough focus on fixing the house. A 2 ton unit will use 2,000W of power, 2.5 tons will be 2,500W. The smaller unit will force lower power bills, but at the possible expense of not keeping setpoint on the hottest afternoons.

  6. #6
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by 54regcab View Post
    If the customer is concerned about power bills then downsizing to a 2 ton would have the same effect as adding 1 SEER point due to longer run cycles. The potential issue is that the unit may not be able to keep up on the afternoons that exceed design conditions. I always say fix the house (reduce heat gain) and use the smallest equipment that will do the job.

    I've seen downsizing make an even bigger impact than that. Maybe 2-3SEER even. I had a home with a 2 ton 9 SEER unit that saw NO energy savings when it went to a 3 ton 16 SEER unit. Acutally energy use might have increased

  7. #7
    Join Date
    Jul 2012
    Posts
    18
    Hey 54 and Moto, I really appreciate your responses. Expecially since no one else wants to jump in on this thread.

    I appreciate your thoughts on down sizing, but I still believe that 500 sqft per ton is appropriate for this location. This condo is in South Padre Island Texas. It is about the same latitude as Miami. Needless to say it is very hot and humid there.

    I also like your ideas about fixing the house; very good advise. Let me explain the construction of this property so you have a better picture. The construction is concrete block, with concrete slabs between the floors. Very typical condo construction. All of the ducting is run through fur downs (dropped ceilings). And the windows are double pain. I'm not sure what the owner could do to improve the insulation.

    I did check the AHRI ratings as Baldloonie suggested. Interestingly the larger air handler (3 ton) is certified with the 14 seer 2.5 ton condenser, but the efficiency and cost of operation are a wash. So as suggested in this thread, the 2.5 ton air handler is the way to go.

    As usual, your guys are right on the money. I appreciate your help!
    Scott

  8. #8
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,480
    500 sq foot a ton does not work. Two houses side by side with same layout could have totally different loads.

  9. #9
    Join Date
    Jan 2007
    Location
    Jacksonville,Fl
    Posts
    123
    Quote Originally Posted by t5800512 View Post
    Hey 54 and Moto, I really appreciate your responses. Expecially since no one else wants to jump in on this thread.

    I appreciate your thoughts on down sizing, but I still believe that 500 sqft per ton is appropriate for this location. This condo is in South Padre Island Texas. It is about the same latitude as Miami. Needless to say it is very hot and humid there.

    I also like your ideas about fixing the house; very good advise. Let me explain the construction of this property so you have a better picture. The construction is concrete block, with concrete slabs between the floors. Very typical condo construction. All of the ducting is run through fur downs (dropped ceilings). And the windows are double pain. I'm not sure what the owner could do to improve the insulation.

    I did check the AHRI ratings as Baldloonie suggested. Interestingly the larger air handler (3 ton) is certified with the 14 seer 2.5 ton condenser, but the efficiency and cost of operation are a wash. So as suggested in this thread, the 2.5 ton air handler is the way to go.

    As usual, your guys are right on the money. I appreciate your help!
    Scott
    Hey Scott,
    I grew up on Padre, my family is still in the business down there. What condo is it, there's a fair chance I ran some ductwork or installed the LV way back when. I definitely agree with your assessment, most of the older condos we're sized under 500 sq ft per ton, lots of loose constuction standards, oceanfront, lots of glass etc. etc. and the Mexican Nationals want it cold in 5 minutes on Easter weekend.

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