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  1. #1

    Fresh air intake and air conditioning

    My house has a fresh air intake that is not dampered. I have a three story house and one system. I keep the fan on all the time to keep the air moving, the AC seems to cool the house and all the rooms are the same temp with the fan on constantly. I assume that the fresh are intake with the fan running constantly just takes in un-AC'd air causing the temp in the house to rise. I have taped over the intake and do notice a difference, question is...is this smart? My guess is that the intake brings in fresh air, so am I causing some type of bad air situation?

    Also, shouldn't the intake be dampered? Thanks for your comments.

  2. #2
    Join Date
    Apr 2008
    Location
    Alberta Canada
    Posts
    2,246

    Depends on Your local codes

    Quote Originally Posted by chum23 View Post
    My house has a fresh air intake that is not dampered. I have a three story house and one system. I keep the fan on all the time to keep the air moving, the AC seems to cool the house and all the rooms are the same temp with the fan on constantly. I assume that the fresh are intake with the fan running constantly just takes in un-AC'd air causing the temp in the house to rise. I have taped over the intake and do notice a difference, question is...is this smart? My guess is that the intake brings in fresh air, so am I causing some type of bad air situation?

    Also, shouldn't the intake be dampered? Thanks for your comments.

    We are not allowed to put manual damper in fresh air. It is their for safety and should not be tampered with. You can get dampers that are tied into gas valve (automatic dampers) and these are legal.
    Do it right the first time.

  3. #3
    Join Date
    Nov 2004
    Location
    Naples, Fla.
    Posts
    1,403
    Fresh air is required:

    1) By many municipal / building codes
    2) To ensure air for combustion (IE: a gas furnace in tight home)
    3) To eliminate VOC and in some cases radon

    Pls have a lic. professional look at for you, IF it can be modulated, he can determine the best procedure.

  4. #4
    Join Date
    Apr 2002
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    11,808
    Quote Originally Posted by 21degrees View Post
    We are not allowed to put manual damper in fresh air. It is their for safety and should not be tampered with. You can get dampers that are tied into gas valve (automatic dampers) and these are legal.
    I don't think it is a combustion air intake

  5. #5
    Join Date
    Apr 2002
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    11,808
    Quote Originally Posted by chum23 View Post
    My house has a fresh air intake that is not dampered. I have a three story house and one system. I keep the fan on all the time to keep the air moving, the AC seems to cool the house and all the rooms are the same temp with the fan on constantly. I assume that the fresh are intake with the fan running constantly just takes in un-AC'd air causing the temp in the house to rise. I have taped over the intake and do notice a difference, question is...is this smart? My guess is that the intake brings in fresh air, so am I causing some type of bad air situation?

    Also, shouldn't the intake be dampered? Thanks for your comments.
    I am assuming this is tied into your return air system.

    If you want to run your fan all the time, get a good motorized damper that opens and closes when the compressor runs.It will still draw in a little air when the damper is closed.

    You do not sound like you live anywhere too humid.Running the fan all the time will even out temperatures plus raise humidity. It is worse when the fresh air is not dampered as you are forcing in a lot of unconditioned air whenever the cooling is not running.

  6. #6
    Join Date
    Apr 2008
    Location
    Alberta Canada
    Posts
    2,246

    Fresh air/ Comb air

    Quote Originally Posted by Carnak View Post
    I don't think it is a combustion air intake
    Fresh air is for prevention of stagmentation and off gases and if heat exchanger ever cracks, helps by keeping up oxygen levels also helps maintain positive pressure inside envelope. And yes it is against code to damper unless interlock with gas valve.

    Combustion air is just that for combustion purposes and sometime pressures.
    Do it right the first time.

  7. #7
    Join Date
    Mar 2007
    Location
    NW AR
    Posts
    2,478
    I dont think hes talking about fresh air in a furnace closet. Hes talking about out-side air thats ducted into his return.

  8. #8
    Join Date
    Jul 2008
    Location
    Rydal,Ga
    Posts
    84

    Ashrea 62.2...

    Chum....

    AprilAir and Honeywell makes a "Fresh Air Damper" activated by temp and RH... and has a manual timer

    A simple calculations is 10 CFM for the home plus 10 CFM per bedroom ....

    "Fresh Air" that is mechanically filtered is nice.... filtered air by walls, floors and attic is not

  9. #9
    Join Date
    Apr 2002
    Posts
    11,808
    Quote Originally Posted by 21degrees View Post
    Fresh air is for prevention of stagmentation and off gases and if heat exchanger ever cracks, helps by keeping up oxygen levels also helps maintain positive pressure inside envelope. And yes it is against code to damper unless interlock with gas valve.

    Combustion air is just that for combustion purposes and sometime pressures.
    I think you are confusing it with combustion air. There is not a whole lot of residential AC in Alberta, and the gas valve is off for a few months of the year.

    I did some subdivisions in Calgary some years back, was an undampered fresh air to the return, and a Hoyme combustion air kit, "interlocked with the gas valve"

    Positive pressure is great when it is humid, not the best thing in the winter in the north

  10. #10
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    Here in Nebraska, Lincoln we are required to put in a 4" fresh air from outside to the return air. This is not allowed to be dampered in any way, motorized or manual. I would check with your local codes department to see what needs to be done in your area.

    Combustion air is a completely different set of codes here and is not related to the fresh air. Without more info it is hard to tell just what we are talking about here.
    Its a good Life!

  11. #11
    Join Date
    Apr 2002
    Posts
    11,808
    4 inch may or may not be enough fresh air

    HRVs usually have a motorized damper that closes when they are off

    Anyone have a code refereence where it is illegal to have a damper in your ventilation air?

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,452
    Quote Originally Posted by chum23 View Post
    My house has a fresh air intake that is not dampered. I have a three story house and one system. I keep the fan on all the time to keep the air moving, the AC seems to cool the house and all the rooms are the same temp with the fan on constantly. I assume that the fresh are intake with the fan running constantly just takes in un-AC'd air causing the temp in the house to rise. I have taped over the intake and do notice a difference, question is...is this smart? My guess is that the intake brings in fresh air, so am I causing some type of bad air situation?

    Also, shouldn't the intake be dampered? Thanks for your comments.
    You may not be getting much air through a 4" fresh air inlet. What is the %RH in the lowest level of the home? My experience indicates that you may only get 30-40 cfm of fresh air through a 4" fresh air inlet. This could be less than an air change every 10-12 hours. Thats enough for oxygen but below recommendations for purging indoor pollutants. 50 cfm is considered minimum for a small house. With the setup you have, you are doing better than most and should not shut the fresh air when you are in the home.
    If you are getting adequate fresh air, your home will get damp like the outside air after a couple days of wet cool weather. In the winter by Jan. the home will be a little on the dry side. Operating your furnace fan in the "Auto" mode when you are not in your home is way to cut back on the fresh air but still maintain the indoor air quality when you are there. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  13. #13
    Wow, I go to bed and look at all these replies. Thanks very much.

    It is fresh air (ducted into the return) and is separate from the air intake for the furnace.

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