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  1. #1
    Join Date
    Nov 2008
    Posts
    6

    Bad supply ductwork(?) - add damper, redo duct, or both?

    Honestly, I don't know if it's bad, but judging from the temperature differential in the house, I need to do something!

    System is a brand new Carrier Infinity 16 4-ton Heat pump/ Air handler, Aprilaire 700A humidifier, and Infinity controller. I only have electric service to the house, no gas.

    The installation went well and the technicians seemed well informed and competent. When I had the estimate done, the 'salesman' (retired installer) wasn't too concerned when he looked at the existing setup, and said that the new system (replacing a 23 year old air handler and a 13 year old compressor) would probably fix the existing upstairs/downstairs heat difference.

    Currently, when the system attempts to reach a temperature of 70 on the first floor, the upstairs will go as high as ~78.

    I've attached (i hope) a picture of the supply ducts as they come off the air handler. The supply that runs off the top of the box is for the 2nd floor. The one that goes out to the right is for the basement and 1st floor. I'm fairly certain that a shoddy job of refinishing the basement entailed adding more runs onto the first floor supply that were never intended to be there. Is it safe to assume that the horizontal run out of the box gets much less airflow than the vertical?

    So, after my long tail of woe, do I:

    A) hire someone to add a mechanical zone damper with an upstairs temp sensor to the 2nd floor supply

    B) have the first floor supply moved to the top of the box and split into two to pass over the I-beam, through the joists, and rejoin the existing rectangular supply

    or

    C) both?

    Thoughts?

    Thanks in advance for this great source of information. It's tough when someone comes to the house and is supposed to be an authority on this stuff, and I as the homeowner don't know enough about it to make an informed decision!
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  2. #2
    Join Date
    May 2008
    Posts
    18
    Unfortunatly you cann't just look at the supply air situation to solve your problem. Are you getting enough return air back to the system from the upstairs? If you have an open stairway a ceiling fan to push the warm air down the stairway may be a more cost effective solution. Good Luck

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Appears the second floor would get the bulk of the air flow.Adding turning vanes to direct more air to the first floor and basement may be a solution,need a Manul J,S and D to determine the best solution.

    Pics showing the connection to the air handler and return duct would help.


    Describe the return duct system too please.

  4. #4
    Join Date
    Nov 2008
    Posts
    6
    There are two returns, none in the basement.

    In the first pic, you can see the return cover up near the ceiling. This is almost an unheated space, as only the 4 beds and 2 baths have ceiling supplies on the second floor. The front room on the first floor only has 1 floor register in it. So for the most part, the air that travels to the 2nd floor would not make its way to this return, and the single supply in the front room isn't enough really to heat the area as things are now.

    The second return is 12' down inline below the first (down those 3 steps.)

    Each of the returns is a 12x10 feeding straight down and coming together into the 12x20 to the return box underneath the air handler.

    The house is ~1000 square feet per level.

    Is it within reason to have the installer come back and do the calculations on the basis that I'm not happy with the system performance? Of course, they weren't done for the estimate. He was basically "Oh, things are working fine, we'll just put in the same size unit that you had"... D'oh! Wish I had found this site sooner!
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  5. #5
    Join Date
    Mar 2008
    Location
    Shelby Twp MI
    Posts
    820
    First and foremost, that supply plenum isn't going to work too good. I would go with a nested fitting (two seperate fittings nested together as one) one being a straight transition for the upstairs and the second an elbow with turning vanes. I would also put a manual volume damper in the straight piece for balancing purposes. The second issue is the return, or lack there of. A 4 ton unit with only a 12x20 return????? Not enough IMO.
    Jim

  6. #6
    Join Date
    Nov 2008
    Location
    Barstow California
    Posts
    14
    Did you have the airflow problems before hand? The trunk line Going upstairs,"maybe",off the top of the unit will always get better airflow.Its straight in line with airflow least path of resistance.It looks like it has a barrometric damper,the little handel with a label of off.If the installers moved this to a full open position that could of changed the airflow upstairs.As dash stated the turning vanes added to the supply plenum could direct air into the downstairs trunk line,one comeing off the side.BUT if installed incorrectly will really screw things up quick.
    You need to have them back out to balance the system,that baro damper will help alot in getting more air to the downstairs but there is a "pretty darn close to perfect position"for it.You can balance the amount of air going to each floor with the damper alone the turning vanes will better direct the air into the downstairs duct.

    Zone systems are a great alternative.They require a bypass duct and room to install it at the air handler.They help with stratafication of the air"Heat riseing" you can set the upstairs at a lower temp,or possibly it wont run as much.You can also turn each zone system on and off depending use,such as down stairs on during the day off at night.lots of differnt options you can fiddle with.Just make sure the contractor has installed zone systems before and ask for pics.

  7. #7
    Join Date
    Nov 2008
    Location
    Barstow California
    Posts
    14
    I will agree on the RA being to small but it doesnt look like you have to many options.Is this a variable speed furnace? Make sure you have someone well versed in sheetmetal do the changes if you decide to go thet rout.for example if they are not experienced enough even a nested fitting can go south sizeing is very important.

    In no way am i puttind a nested fitting down,actually its a great idea,we call it a pair of pants!not quite the same but close,fitting wise.it has to be sized correctly though,it will always be easier for air to go upstairs,hencebalanceing dampers.If sized correctly possibly no dampers!!

  8. #8
    Join Date
    Nov 2008
    Posts
    6
    Thanks for the responses.

    I did have the same heating imbalance before the new system was installed. The old system actually failed, so I took the advice of the salesman (former installer, he said "wait and see") and have lived with the new system for about 3 weeks now. Obviously, the new system did nothing to affect the imbalance, and is actually a bit worse now.

    I am certain the damper in the 2 floor supply line is fully open, as it was before - I checked.

    Would adding returns in the basement help at all? Could I have returns run into the attic and down between the studs in the upstairs rooms?

  9. #9
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Ask them to show you the static on the Infinity Controller(User Interface),likley too high ,based on the pics.


    Duct remediation by a pro is needed.

  10. #10
    Join Date
    Nov 2008
    Posts
    6
    What should the static pressure be?

    Dash, is it reasonable to get the installers back out and ask them to perform the calculations and measurements that should have been done in the first place, or will the just shrug and tell me too bad?

  11. #11
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by Speqtre View Post
    What should the static pressure be?

    Dash, is it reasonable to get the installers back out and ask them to perform the calculations and measurements that should have been done in the first place, or will the just shrug and tell me too bad?
    They could tell you on the phone how to read the static on the Infinity Control/stat.

    Your ducts were likely done by others ,so remediation may be at your cost.We try to test/check ducts and include the costs to fix them ,in our replacement proposal.When we miss something,we ask the customer to pay have the cost of duct remediation,some refuse and we end up eating the cost.Can't say what your contractor will offer.

    Also the mfrs. instructions/design data, include maximum operating statics for supply and return,so they could/should have attempted to meet those.

    Static needs to be < .7 ,IMHO.The control only gives you the sum of the supply and return,they can test them separately and should ,as the return needs to be < .4 ,to prevent water blowing off the coil,that can damage the motor.

  12. #12
    Join Date
    Nov 2008
    Posts
    6
    I wasn't proposing that the installer pay for any remediation work on the ducts, just that maybe they should come out and provide an estimate and take the time to do some of the calculations this time.

    They didn't submit anything regarding the ductwork in their install proposal, and didn't perform any of the Manual J, S, or D calculations.

  13. #13
    Join Date
    Nov 2008
    Posts
    6
    So I read the static pressure off the control when I got home. In High heat mode, with airflow @ 995 cfm, static pressure was only .15.

    What does this tell me?

    Should I just close the manual damper to the 2nd floor somewhat and see how that works out?

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