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  1. #1

    Placement of ducts

    I have an average size bedrrom (10' x 12'). It has an 8' ceiling. The temp in this room is running about 3 degrees cooler than the rest of the house. It is heated by a Heat Pump. I know this is not a HUGE difference, but it is noticable and I have an idea that might fix it. Before I give you my idea, let me give you a little more background. The dampers for the this room are fully open. My contracator and I are hesitant to adjust the dampers in the other rooms b/c we are both very happy w/ the temperature consistency in these rooms (all 7 of them). The 'cold room' is the only one on the second floor. The Airhandler is in the basement, compressor outside (of course).

    The 'cold room' has a supply duct and a return. I am not sure of the size of them, but tearing them out and putting in new ones seems like overkill and may screw up the other rooms. The are located in the walls (knee high). There is no attic above the rooms. The ducts cannot be moved to the floor b/c there is living area below the floor. Neither one can be raised in the wall b/c the flex ducts actually reside in 'cubby holes' that run parallel to the room and only have 4' high celings.

    The supply and the return were placed directly across from each other on the resppective walls (10' across from each other). The grill that was used in the supply blows the air straight out, not sideways. This was done so air would not blow directly at the people in the bed.

    My thought is to move the supply laterally on the wall so it is not directly across from the supply, but instead have it diagnolly across the room from the return.

    My contractor will do it for me but does not seem to think it will make much (if any) of a difference. Thoughts?

    Thanks.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    I agree,not much if any difference.

    Most anything you do,to get more air to that room,will have an effect on the others,as you will not be creating more,the others will get less.Done properly that's not an issue.

    If it's the farthest room from the indoor unit,reducing the static(resistance of ducts to air flow),will allow more available static to move air to the farthest rooms.


    In rare cases,we have converted the return duct in a room,to a supply duct to get more air,and added a jumper return to the room.

    Does the room heat better if the door is left open??

  3. #3
    Join Date
    Sep 2006
    Posts
    1,253
    Quote Originally Posted by ivanl3 View Post
    I have an average size bedrrom (10' x 12'). It has an 8' ceiling. The temp in this room is running about 3 degrees cooler than the rest of the house. It is heated by a Heat Pump. I know this is not a HUGE difference, but it is noticable and I have an idea that might fix it. Before I give you my idea, let me give you a little more background. The dampers for the this room are fully open. My contracator and I are hesitant to adjust the dampers in the other rooms b/c we are both very happy w/ the temperature consistency in these rooms (all 7 of them). The 'cold room' is the only one on the second floor. The Airhandler is in the basement, compressor outside (of course).

    The 'cold room' has a supply duct and a return. I am not sure of the size of them, but tearing them out and putting in new ones seems like overkill and may screw up the other rooms. The are located in the walls (knee high). There is no attic above the rooms. The ducts cannot be moved to the floor b/c there is living area below the floor. Neither one can be raised in the wall b/c the flex ducts actually reside in 'cubby holes' that run parallel to the room and only have 4' high celings.

    The supply and the return were placed directly across from each other on the resppective walls (10' across from each other). The grill that was used in the supply blows the air straight out, not sideways. This was done so air would not blow directly at the people in the bed.

    My thought is to move the supply laterally on the wall so it is not directly across from the supply, but instead have it diagnolly across the room from the return.

    My contractor will do it for me but does not seem to think it will make much (if any) of a difference. Thoughts?

    Thanks.
    Location of the return will have minimal impact on the temp in the room. What you should do is determine the amount of air flow that room needs. To do that a Manual J calculation must be done on a room by room basis (download program from this site). This will tell you the heat gain and loss and the required air flow per room. Then your contractor (if this one can't or doesn't have the equipment then find one that does) must measure the actual air flow from each supply. It is likely that a little extra air is going to several places when it needs to go to this room. Tweaking the dampers will then get the air flow correct in all rooms. Testing and measuring will provide the data necessary to make corrections that will work. The rest is guessing.

    Also, since this room has knee walls you should make sure that it is properly insulated against attic air. Often the walls will only have R11-13 when they are subjected to the same high temps as the rest of the attic that is insulated at much higher levels. Second thing to check is to make sure that attic air can not get under the floor of that room (very easily done in this situation). Either or both of these situations will make it very difficult to keep that room comfortable.

  4. #4
    Quote Originally Posted by dash View Post

    If it's the farthest room from the indoor unit,reducing the static(resistance of ducts to air flow),will allow more available static to move air to the farthest rooms.
    How does one reduce the static?

    Quote Originally Posted by dash View Post

    Does the room heat better if the door is left open??
    Can't say for sure as the door has been left open the entire time since the system has ben installed. But I am fairly confident the answer is yes....

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by ivanl3 View Post
    How does one reduce the static?



    Can't say for sure as the door has been left open the entire time since the system has ben installed. But I am fairly confident the answer is yes....
    System static can be reduced by adding turning vanes to elbows near the indoor unit,or adding another return duct and grille,plus many other things.

    If the room does better with the door open,then it needs a better return.Test by running the system,feel the supply air with the door open,then have someone close it,if supply air quantity drops,you have a lack of return.

    Can only get supply air in the rioom if it has a low resistance path back to the return of the unit.Just like you can't blow air into a closed paper bag,unless it has a path to get out.

    Return paths,when ducts can't be added, can be under the door,thru a wall,or from ceiling to ceiling,from the room to the hallway.

  6. #6
    Join Date
    Jan 2008
    Posts
    91
    Say you have a situation where you only have returns on the first floor of a two-story. Does it make sense to have a jumper installed to connect the first and second floor?

  7. #7
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by Cub View Post
    Say you have a situation where you only have returns on the first floor of a two-story. Does it make sense to have a jumper installed to connect the first and second floor?
    All rooms need to have a return path or ducted return(baths and kitchens ,no ducted returns).Could be to the second floor hallwway,assuming that's open to to the fisrt floor via the staircase.

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