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  1. #14
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,396
    If a 1.5 ton cooled and dehumidified well but ran all the time, what in blazes are you doing over doubling the size? You had better be ripping all the ducts and putting over double the duct capacity in too. And increasing the number of supply & return vents.

    I can't believe 2500 sq ft in CT needs 3.5 to 4 tons. You'll barely run and have high humidity, even the 2 stage since low isn't much less than high .Then you'll need a whole house dehumidifier.

    You likely will never recoup the investment for 16-17 SEER either. Good for the salesman's commission which is likely why Mr. Trane was pushing them. Rheem is good equipment but 4 tons without changing the main duct size???? Wow, you have some real winners up there.

    Somebody better find out what you have (if you can post model #s in & out we can tell you, somebody, even you, should do an accurate heat gain, then see what you need. But if you kept comfy with 1.5 ton and only complaint is higher than desired bill, you sure don't need those monsters being quoted. Short cycling and if they reuse that small duct system, you may not see much of a savings.

  2. #15
    Join Date
    Apr 2013
    Posts
    90
    Quote Originally Posted by BaldLoonie View Post
    If a 1.5 ton cooled and dehumidified well but ran all the time, what in blazes are you doing over doubling the size? You had better be ripping all the ducts and putting over double the duct capacity in too. And increasing the number of supply & return vents.

    I can't believe 2500 sq ft in CT needs 3.5 to 4 tons. You'll barely run and have high humidity, even the 2 stage since low isn't much less than high .Then you'll need a whole house dehumidifier.

    You likely will never recoup the investment for 16-17 SEER either. Good for the salesman's commission which is likely why Mr. Trane was pushing them. Rheem is good equipment but 4 tons without changing the main duct size???? Wow, you have some real winners up there.

    Somebody better find out what you have (if you can post model #s in & out we can tell you, somebody, even you, should do an accurate heat gain, then see what you need. But if you kept comfy with 1.5 ton and only complaint is higher than desired bill, you sure don't need those monsters being quoted. Short cycling and if they reuse that small duct system, you may not see much of a savings.
    Well every single person has recommended a 3.5-4.0 ton unit. I was incorrect (rather one of the salesman was incorrect) on the outside unit being 1.5 ton - it's 3 ton and the air handler is a 3.5 ton unit. This guy is the only one who did the heat lost/gain and every single neighbor with a similarly sized house built by the same builder in 1953 has a 3.5 to 4.0 ton so I don't find the size shocking. Also, it's a ranch with a very large roof, lots of attic volume and lots of very large unshaded southern-exposed windows.

    He said going to a 4 ton from a 3.5 ton that the main duct will be fine (it is slightly oversized for a 3.5 ton system), he will need to add a return (there are already two) and runs may need to be added and sizes adjusted based on cfm requirements of the individual rooms.

    Lastly where are you from? Don't discount how hot and humid southern CT can be in summer especially along the Sound where you don't get the ocean breezes - just the added evaporative humidity.

  3. #16
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,468
    Quote Originally Posted by idmd View Post
    Company one came out to calculate a heat gained/lost. Measured all the rooms and input all the variables and because of one room furthest from the air handler on the southern side of the house with large windows on 3 sides it bumped the requirement from 3.5 ton to 5 ton - he said that room alone (maybe 12x12') requires nearly a ton of cooling itself.

    Obviously 5 ton would add a significant amount $. He said if he changed the parameters from cooling the house to 75F on a 95F day to 77F on a 95F day the 4 ton works. He said I need to add another air return to do this and that the room in questions would likely be a few degrees warmer. As it is with the current system there could be as much as an 8-10F difference with just that room. I'm thinking after sealing/insulating and upgrading that should be more like 2-3F on the warmest days?

    This stuff is really outside my knowledge - what do the experts think?
    Click on http://hvac-talk.com/vbb/showthread....1#post15583161 and read the post again.

    If your 3-Ton ran steady at the worst conditions then it was sized right; though it may not have been delivering to & from the rooms near its Rated Performance. They can't size replacement units by un-performance tested existing units; the existing system may need work to improve its performance!

    There is NO way you can go to 5-Ton on that duct system & Return Air Filter sizing, etc., don't even consider it; please don't make any equipment decision until the Home Energy Audit & any needed Retro-work is completed.

    Please don't get the cart before the horse; You could make a costly mistake that you will regret for the life of the equipment.


    Were it me, I would use a separate system for the distant room that is running the load-calc way up. The design conditions show that humidity is probably the biggest problem not temp; therefore, never oversize the A/C, as it needs long runtimes.

    Check the duct system & return Air filter area sizing should be for 300-fpm velocity through a 1" deep fiber glass filter (Manual D, Bet they don't know that); you have to keep the pressure drops low...You make the call, you live with an efficient result or, with a very costly result...

  4. #17
    Join Date
    Apr 2013
    Posts
    90
    Alright, I have his load form in front of me now.

    Total sqft = 2510
    Total required cooling 47602 Btuh @1600 cfm
    Total required heating 75825 Btuh

    The "sun room" in question is 192 sqft (bigger than I thought) and he calculates in needs 276 cfm. Some rooms like the dinning room have too much flow as is and some like the very large living room don't have enough. Interestingly the "sun room" is the most cooling intensive room in the house even compared to the 464 sqft living room that only has one externally exposed wall and one large window.

    As always comments welcome.....

  5. #18
    Join Date
    Apr 2013
    Posts
    90
    Quote Originally Posted by udarrell View Post
    Click on http://hvac-talk.com/vbb/showthread....1#post15583161 and read the post again.

    If your 3-Ton ran steady at the worst conditions then it was sized right; though it may not have been delivering to & from the rooms near its Rated Performance. They can't size replacement units by un-performance tested existing units; the existing system may need work to improve its performance!


    There is NO way you can go to 5-Ton on that duct system & Return Air Filter sizing, etc., don't even consider it; please don't make any equipment decision until the Home Energy Audit & any needed Retro-work is completed.

    Please don't get the cart before the horse; You could make a costly mistake that you will regret for the life of the equipment.


    Were it me, I would use a separate system for the distant room that is running the load-calc way up. The design conditions show that humidity is probably the biggest problem not temp; therefore, never oversize the A/C, as it needs long runtimes.

    Check the duct system & return Air filter area sizing should be for 300-fpm velocity through a 1" deep fiber glass filter (Manual D, Bet they don't know that); you have to keep the pressure drops low...You make the call, you live with an efficient result or, with a very costly result...
    The reason the 5 ton would be significantly more is because he said all the duct work would been to be replaced....with the 4 ton he says we can use the main supply and since we're changing out all the runs anyway they can be properly sized.

  6. #19
    Join Date
    Apr 2013
    Posts
    90
    Here are his calcs

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  7. #20
    Join Date
    Apr 2013
    Posts
    90
    Alright....in the middle of the change out. Air handler (Trane Tam7) and condenser (xl15i - 4 ton) is installed and now they are working on the duct work. Turns out main duct was internally insulated with a 1" fiberglass duct liner. Their plan is to keep this because it was done well and in good shape and then use 3" fiberglass duct wrap. Installer said it should give around an R11.

    Any reason to question whether or not internal insulation should be removed?

  8. #21
    Join Date
    Apr 2013
    Posts
    90
    So finishing an energy audit that could not be completed because the AC died. New AC is in but the audit guy made the following comments - overall they did a good job with the exception of:

    1. There is 1/2" space between the air handler and supply duct around the bottom.

    2. The 90 degree elbows that lead into the vents were not sealed with mastic.

    As a consequence the system is not sealed properly and I don't qualify for a $500 rebate until that's done.

    System is 2 weeks old. What do you think about these comments? How would you approach install company?

    Thanks

  9. #22
    Join Date
    Apr 2013
    Posts
    90
    Starting new thread

  10. #23
    Join Date
    Aug 2012
    Location
    Gulf Coast
    Posts
    94
    I grew up in belchertown ma, and didnt have ac untill a week before i left for bootcamp and dad bought "me" a window shaker. We used to hang sheets in the doorways n open windows at night... And the house never got above 78/58rh i love seeing the big ac boom up there though.

  11. #24
    Join Date
    Apr 2013
    Posts
    90
    Quote Originally Posted by ReferYankee View Post
    I grew up in belchertown ma, and didnt have ac untill a week before i left for bootcamp and dad bought "me" a window shaker. We used to hang sheets in the doorways n open windows at night... And the house never got above 78/58rh i love seeing the big ac boom up there though.
    Southern coast of CT gets warm and particularly humid at night. Tonight for example it's only 64F out but the humidity is 95%. We have long stretches in the summer where the temp is 80F+ with high humidity at night - windows or fan I'd probably wake up in a puddle of sweat without an AC on those nights

  12. #25
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,947

  13. #26
    Join Date
    Apr 2013
    Posts
    90
    So today is our first 90F day with 45% himidity and really the first day the AC has been "needed". Still have some improperly sealed ducts so things may get a little better. I set the tstat at 68F just to see if it could cool that low. My new system is a 4 ton which replaced a 3.5 ton and there was some discussion it maybe too big. With the tstat set at 68F the system has run constantly all day and has maintained 70F inside.

    On a positive note the kitchen and sun room which have large windows and a southern exposure are much more consistent with the rest of the house. The sun room used to be 8 or 9 degrees warmer on a 90F day and today it's been 73.5F all day with full sun.


    It's my understanding a properly sized system will lower inside temp 20F. Is this correct? Is this the type of performance you would expect?

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