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  1. #1
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    Feb 2008
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    Air return duct size question

    We had a new heat pump system installed a few years ago (Trane XL14i). I just got to looking at the air return duct and it goes from a 20 x 30 filter size to less than 10x 20 in the duct work before it goes to the blower(not real sure about the terminology here).

    Is this normal?


    Thanks

  2. #2
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    Jan 2008
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    Size matters. As in furnace size, heat pump, and the rest of the return system. A few more details will get you some answers from someone around here.

  3. #3
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    Model numbers or eqipment size needed to comment on duct sizes.

    Complete description of duct system and/or pictures,for more informed comments.

  4. #4
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    The only way to truly tell is to have pressure drop tests done. Static pressure, the amount of pressure exerted on the walls of the ducting, is normally rated based on 100 foot of ducting, which no residential system has.

    The filter area naturally needs to be larger because a filter is not an open area device and needs to be larger to not block air flow. So at least that part of your system is normal.

    Why do you ask about this? Are you having issues with your HVAC system? Common issues with air flow problems would be furnace overheating in the winter or indoor coil freezing up in the summer cooling mode.
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  5. #5
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    Quote Originally Posted by RoBoTeq View Post
    The only way to truly tell is to have pressure drop tests done. Static pressure, the amount of pressure exerted on the walls of the ducting, is normally rated based on 100 foot of ducting, which no residential system has.

    The filter area naturally needs to be larger because a filter is not an open area device and needs to be larger to not block air flow. So at least that part of your system is normal.

    Why do you ask about this? Are you having issues with your HVAC system? Common issues with air flow problems would be furnace overheating in the winter or indoor coil freezing up in the summer cooling mode.
    Major correction,Friction Rate is based on static per 100 feet or equivalent feet of duct,not static,very common mistake by many,NATE testing shows many don't undestand.

    Static or better yet External Static,is the actual pressure of "things' external to the equipment,could be coil,filter,grilles,duct,etc..


    Testing the ESP is a first step,also looking at the ducts and using Manual D ,based on what's installed is an excellant method to resolve issues.
    Last edited by dash; 02-09-2008 at 10:36 PM.

  6. #6
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    Feb 2008
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    NC
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    Quote Originally Posted by RoBoTeq View Post

    Why do you ask about this? Are you having issues with your HVAC system? Common issues with air flow problems would be furnace overheating in the winter or indoor coil freezing up in the summer cooling mode.
    Ok, it is 3 Ton split heat pump, 14 seer, outdoor section model # 4TWX4036A1000AB, Indoor section model# 4TEE3F37A1000AA

    Some more info:


    This is in my mother's house and I have never taken a good look at it, but it just seems like it costs more than it should to heat in the winter. Last month's power bill was $290. This is a 1750 sg ft house. In the summer, power bill is usually $140 or less.

    I just started looking at it closer because I had to replace the thermostat. I flipped the breaker in the house before starting. When I put the new thermostat on (Honeywell RTH7500), it wouldn't power up. I put the old one on and it wouldn't power up either

    I finally found the fuse that was blown after pulling off panels here and there, it was on the red wire by the way. There was a separate breaker outside at the power meter just for the heat pump, I guess they must have ran this new line when they installed it. They just busted out some mortat between the brick foundation and stuck the wire through

    Anyway, i got to looking under the house and noticed some insulation around the ducts going to the vents was sparating and hanging down. Granted, it has been almost 5 years since the installation. Should the connections between the pieces of duct have been sealed some way? They just had pieces of insulation cut out for each side of the duct and then duct taped over. I just found the contract and it states "Ductwork looks to be in good shape and we'll vacuum out and mastic/caulk seal all joints, we'd remove all grilles and seal any penetration thru the floor, to enlarge the return to at least 20x25 or add second one in another area of the home..."

    Another thing I am not too happy with is the vents in the rooms. Included in the installation was new vents in all the rooms. The new vents are about 4 inches wider than the old ones were and thinner. Here is a picture of how they left them:




    This cost $ back in 2003, which seemed like way to much to me. Can anyone tell me if this was a reasonable price?



    Thanks for the replies so far
    Last edited by jrbenny; 02-10-2008 at 10:44 AM. Reason: pricing removed

  7. #7
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    A pic of how it connects to the furnace would help.

    A reasonable price to us, may not be reasonable to you.

    As you can see, jr was a little slow today removing it.
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  8. #8
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    Dec 2007
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    oregon
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    Some furnace supply and return pleunms have combined friction or TEL of over 200 feet just by themselves! thats before wet coil,and filter ect. Then theres the trunkline, longest branch and then the registers and grille friction. many systems with box and can trunk and plenums have a TEL of over 300-400 feet! Just by putting in 6x10 instead of 4x10 boots can save substantialy on friction. The grilles in that picture don't look to fit the boot to well.
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  9. #9
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    Quote Originally Posted by adama View Post
    Ok, it is 3 Ton split heat pump, 14 seer, outdoor section model # 4TWX4036A1000AB, Indoor section model# 4TEE3F37A1000AA

    This is in my mother's house and I have never taken a good look at it, but it just seems like it costs more than it should to heat in the winter. Last month's power bill was $290. This is a 1750 sg ft house. In the summer, power bill is usually $140 or less.

    ... (Honeywell RTH7500), it wouldn't power up. I put the old one on and it wouldn't power up either.

    There was a separate breaker outside at the power meter just for the heat pump, I guess they must have ran this new line when they installed it.

    Anyway, i got to looking under the house and noticed some insulation around the ducts going to the vents was separating and hanging down.

    Granted, it has been almost 5 years since the installation.

    Another thing I am not too happy with is the vents in the rooms. Included in the installation was new vents in all the rooms. The new vents are about 4 inches wider than the old ones were and thinner. Here is a picture of how they left them:
    By the looks of that grille and energy cost, you must live in Ohio.
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  10. #10
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    nope, North Carolina... This was installed by a very reputable company by the way.

    So, what about the part of the proposal that reads "Ductwork looks to be in good shape and we'll vacuum out and mastic/caulk seal all joints"?

    What exactly does this mean? Should there be some sort of sealant between all joints in the ducts? Did they skip out on this part and just cover up with taped on insulation? What is the standard procedure for something like this?

  11. #11
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    Quote Originally Posted by adama View Post
    nope, North Carolina... This was installed by a very reputable company by the way.

    So, what about the part of the proposal that reads "Ductwork looks to be in good shape and we'll vacuum out and mastic/caulk seal all joints"?

    What exactly does this mean? Should there be some sort of sealant between all joints in the ducts? Did they skip out on this part and just cover up with taped on insulation? What is the standard procedure for something like this?
    I'd ask them about it,Mastic/caulk all joints,could be just accessable ones,or those in the insulation.If it wrapped metal,all wrwp9insulation) would have to be removed to mastic the metal joints,which would be costly.

    Again, ask them and get a response.

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