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Thread: Undersized AC

  1. #1
    Join Date
    Aug 2011
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    Undersized AC

    Please guide me on how to handle my situation.


    I just put Central Heating and Air in a rental house. Older home with single pane windows. Originally had window units so it now has all new ductwork.

    House is just over 1,000 sq/ft.

    AC guy Said the load calculation called for a 2 ton unit. That seemed low to me considering it is a old house with single pane windows and unknown wall insulation. He assured me that it would cool fine.

    About 2 days into the install everything was going great. Ductwork was all in. Air handler was in place. Guy said he had a friend coming to help set up the outside condenser that evening and he would be finished.

    He asked to be paid because it was friday and he was going to finish that day....... I paid him and boy did things change....

    He didn't answer my call for a week and finally 3 weeks later he finished the install... *Still Hasn't ran the exhaust for the heat"


    After he finished the install it seemed to be cooling quiet well, but it was raining every day that week and the outside temperature wasn't nearly as high as usual...


    A few days after he finished my tenant moved in and has been complaining that the AC never shuts off and will not reach the set temperature even when it's set high. (80). Tenant is worried that the electric bill will be astronomical and has just decided to do without AC.... I don't know how considering it has been 95-100 every day lately. HOT A$$ south MS.


    After talking to another AC guy he said the unit is too small by at least 1/2 a ton.


    How do I handle this situation. The AC guy is a local independent installer. The equipment is a 2ton Rheem gas furnace unit *13seer* Attic was has brand new blow in insulation covering the rafters.

    Thanks for any help or guidance.

  2. #2
    Join Date
    Aug 2000
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    Central Oregon
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    A load calc is the only way to truely tell if the unit is undersized. 2 ton would generally suffice for 1000 sqft. He may be low on refrigerant also, or could be a duct work issue.
    If you think our goverment is screwed up. You haven't lived in another country.

  3. #3
    Join Date
    Feb 2010
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    Cal
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    Equipment will produce it's rated capacity with 95 outdoors and 80 indoors, duct leakage is subtracted to give delivered capacity. Sized correctly and based on regional weather data, the equipment would not keep up 1% of the time and running continuously. If you're in one of the areas with abnormally high temps this year, I wouldn't be surprised by the performance.

    Getting a second opinion from an impartial/qualified contractor might cost a few hundred, but could be the quick solution with the least frustration. If you are indeed in a real hot area, it could take a while before you could get someone there to see if the system was installed and commissioned correctly.

    Check out the AOP map and see if the forum has a member serving your area.

    Good luck

  4. #4
    Join Date
    Aug 2011
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    I live in South MS and the average High is 92. We regularly see High 90's and triple digit temps. We also have ridiculous Humidity... It's like we live in the sweaty armpit of America. I hate it and hope to move to San Die ago someday lol...

    That being said. My home and office AC do run for long periods of time during these hot days, but they will definitely cycle on and off if the thermostat is on 80.


    My question is this. If it is determined that the AC is indeed undersized and can not operate properly. Would the AC guy be liable for replacing it???


    He's a nice guy and talks a good game, but I've just caught him in several concerning incidents.

    1) Said it would be finished on Friday and disappeared on vacation for a week.

    2) Said he was finished and it was working. I went over and noticed that there was no air coming out of the bedroom register. I go up in the attic and notice that there is NO DUCTWORK CONNECTING THAT REGISTER AND THE PLENUM.

    3) I also noticed the gas wasn't hooked up for the furnace and there was a bad leak coming from the side of the plenum.

    4) After he hooked up the gas line and sealed the air leak with duct tape I realized he didn't run the exhaust vent for the furnace. He made up some bs excuse how my handy man volunteered to do it. *LIE*

    5) He was supposed to be doing some plumbing work and A)Broke my toilet tank lid cover B) Lied and said that the tub had a crack when it actually needed a drain kit. C) He didn't stub out the lines far enough on my shower knobs *Can't fit Shroud behind handles*


    needless to say I'm a bit leery of his diagnosis of anything. Guy has really disappointed me.

  5. #5
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    There's no guaranty that it's actually providing 2 tons of cooling. (Is the unit moving at least 800 cfm? Charge correct? Ductwork sealed and insulated if in attic? Refrigerant charge correct)

    Did the guy actually check insulation levels (walls, attic), or just guess.

    If it's too small, improving the house is preferable to up-sizing.

    Single pane windows can be improved with shrink wrap. There are also low-e window films available.

    Upgrading the attic insulation might be a good option, especially if it's below R-25.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  6. #6
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    oregon
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    Question. The guy that did the install is he more of a handy man or a guy that specializes in hvac? Also did he pull permits? The reason I ask is the company that did my install does not do plumbing and if inspected I would hope the inspector would have caught that the gas was not hooked up.

  7. #7
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    Good eye Grizzle. I think you're on to something, I know my company wouldnt leave venting for a "handy man". It's our job, our name, if something goes terribly wrong, it's our ass on the line.

  8. #8
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    Aug 2011
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    Quote Originally Posted by amd View Post
    There's no guaranty that it's actually providing 2 tons of cooling. (Is the unit moving at least 800 cfm? Charge correct? Ductwork sealed and insulated if in attic? Refrigerant charge correct)

    Did the guy actually check insulation levels (walls, attic), or just guess.

    If it's too small, improving the house is preferable to up-sizing.

    Single pane windows can be improved with shrink wrap. There are also low-e window films available.

    Upgrading the attic insulation might be a good option, especially if it's below R-25.


    The ductwork and air handler are are in the attic. Attic has ridge vent and vents at the eves.

    The ductwork is just flex material and un-insulated. Didn't realize there was a difference until going up in my home attic just now..... I imagine that could be making a big difference.

    A-Hole said the charge was perfect.


    I feel like such a idiot.... I usually read up on big purchase items for days before making a decision. I just expected the guy was a professional and wouldn't install something improperly for liability reasons.

    I'm going to try and paint a picture of the layout.

    The Intake/Return air is in the ceiling of the hallway where the old attic fan used to be. It looks like a 24"-30" flex tube connecting it to the Air Handler which runs to the sheet metal plenum.

    The Plenum has 4 Outlets on one side and 3 on the other. From the plenum there is just flex duct work going to the registers.

    The unit seemed to be working fine when it was in the mid 80's and overcast. The Tstat was set on 75 and it would cycle on and off.

    Unfortunately I wasn't able to spend any time in the house on a real hot day before my tenant moved in.


    No permits were pulled for the installation. I honestly wasn't wanting to haver inspectors pilfering around in my old house.


    I've asked my tenant to set the ac down to 75 tonight and let me come by tomorrow at mid day to see how it's doing. It's very hard to trouble shoot something when there is someone else living in the house.

  9. #9
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    Quote Originally Posted by grizzzlle View Post
    Question. The guy that did the install is he more of a handy man or a guy that specializes in hvac? Also did he pull permits? The reason I ask is the company that did my install does not do plumbing and if inspected I would hope the inspector would have caught that the gas was not hooked up.
    He's primarily Heating and Air and Electrical. Business Cards, and supposedly a platinum seller (Or some fancy title) for Rudd/Rheem. I believe he said it meant he did over 100K annually for that particular brand.

    The guy is in his Late 30's early 40's and said his dad is also in the business.

    His assessment is that the tenant is setting the unit up too high because of fears of high electric bills. He said the Unit will produce a 18-20 differential between outside temp and inside.


    If the unit is only 1/2 ton too small I guess I could put a 6,000 btu window unit back in the master bedroom to help with the load... That would probably be the cheapest route I can imagine.

  10. #10
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    Uninsulated duct work? Uh oh. What level of "bad" are we talking about here?
    Post some pics if you get a chance.

  11. #11
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    Rochester NY
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    Hey, my house is hot!

    ...... Well, turn on the ac.

    Hey, the ac is always running.

    ..... Then turn it off.

    But then the house will be hot.

    Try telling your tenant this:

    I get it, you want the house cool WITHOUT having the ac running. I'd like to drive to Florida without turning the car on, but ain't gonna happen. And don't let me catch you smokin those funny cigarettes on my property...
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  12. #12
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    If the unit is undersized by even 1/2 a ton, the house has some major problems which a 2.5 or 3 ton system won't solve.

    If the ducts aren't insulated at all, you could easily be losing 40% or more of your capacity. Throw in other major problems with the install (charge, airflow, leakage) and your 2 ton unit could be providing 1 ton or less of cooling.

    55-60F degree air can pick up a lot of heat when the ducting runs through a 120F+ degree attic.

    That being said, a 2 ton unit in a house with little or no insulation and single pane windows should run a lot (continuously at times) when the od temp is above 90F.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  13. #13
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    Aug 2011
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    Quote Originally Posted by btuhack View Post
    Uninsulated duct work? Uh oh. What level of "bad" are we talking about here?
    Post some pics if you get a chance.
    Planning on it tomorrow. Not sure if they are completely un insulated but they look nothing like what is in my home.

    I've got a feeling this guy has dropped the ball badly. Just based on his actions thus far. How bad I'm not quiet sure.....

    I'm guessing he was wanting the work so therefore submitted a offer that was too low to afford doing it properly to ensure he got the work.

    He charged $$$$$ for parts and labor---Which seemed low. I was expecting no less than $$$$$ Therefore I wasn't planning on doing it for a rental house. His price fit within my budget and I assumed he would provide me with a new and functioning system.



    I wish so badly that I would have just replaced the stinking wall units and not have bothered with central heating and air.... I looked like it as a investment. I was hoping it would be more appealing to my tenants and also improve the value of the home when I decided to resell..... Being as my tenant has elected to just do without air conditioning instead of letting this thing run 24/7 I assume this investment has back fired..


    Back to the original question. Is there any recourse?
    Last edited by Chris_Worthington; 08-14-2011 at 11:45 AM. Reason: Pricing Removed

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