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  1. #1

    Hooking up in line fans to boost temperature in one room

    My Comfortmaker system was installed and two in line fans were added to boost the output to one room. The fans were wired to an always on AC connection and as far as I can tell have both burned out over time. I am about to replace them and I see two options - hook them to an AC line that receives power when the furnace is running or hook them to duct stats. My preference is to do the first because it is cleaner, less things to go wrong. I cannot find any documentation on my furnace so I was wondering if anyone had any links to information that will help me figure out if there is a switched 110v coming off the furnace for running accessories? Thanks.

  2. #2
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Thread relocated to AOP

  3. #3
    Join Date
    Sep 2002
    Location
    Northeast Ohio
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    4,842
    Care should be taken not to exceed the amp capacity of any control boards or controls on your furnace. Doing so will cause over loads resulting in failures that will be expensive. There are several ways to achieve what you want but site rules prevent any detailed DIY instructions. Any competent local HVAC professional should be able to help you with this.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  4. #4
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Two inline fans to boost output to a single room?

    Has anything else been done to balance the system?

    Duct fans should be a last resort after everythign else has been tried.

    Fantech makes some good quality inline mixed flow fans. I have one in my home exhausting my garage that's going on 1-1/2 years running continously.

    I would power it seperate of the furnance and use a relay triggered by the "EAC" output on the furnace board so it runs when the furnace blower runs only.

  5. #5
    Thanks for the help. The relay sounds like the way to go. I don't want the fans running all of the time as it will reduce their life and consume electricity. The room is on the outside of the house - a converted porch - with windows on three walls - so it is always cold or hot depending on the season. I am not sure why two fans were installed - I will try hooking them up one at a time.

    Quote Originally Posted by motoguy128 View Post
    Two inline fans to boost output to a single room?

    Has anything else been done to balance the system?

    Duct fans should be a last resort after everythign else has been tried.

    Fantech makes some good quality inline mixed flow fans. I have one in my home exhausting my garage that's going on 1-1/2 years running continously.

    I would power it seperate of the furnance and use a relay triggered by the "EAC" output on the furnace board so it runs when the furnace blower runs only.

  6. #6
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,302
    Did the room ever stay comfortable when the booster fans worked?
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  7. #7
    I can't remember. I don't know how long it has been since the fans have been working. The room is always cold.

    Quote Originally Posted by Shophound View Post
    Did the room ever stay comfortable when the booster fans worked?

  8. #8
    Join Date
    Oct 2007
    Location
    Chicago, IL
    Posts
    56
    Quote Originally Posted by simonmason View Post
    I can't remember. I don't know how long it has been since the fans have been working. The room is always cold.
    Think I would spend my time and money on insulating and draft-sealing the room. Converted porch will never be comfortable unless these issues are addressed first, especially with that amount of windows. Boost fans alone will not do the trick.
    More than likely insulation is poor at best, that is where I would look first, if you want to actually make the room usable.

    Hiptech

  9. #9
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,302
    Quote Originally Posted by simonmason View Post
    I can't remember. I don't know how long it has been since the fans have been working. The room is always cold.
    If you cannot remember the room ever being warm, either rhe booster fans have been burned out forever, or they never did any good in the first place. My money would be on the latter bet. Furthermore, I would bet that if you pulled the booster fans out of the duct and then patched the duct where the fans were, the room might actually feel a little warmer. Not much, but more than you have had so far.

    By how you describe the addition, it is a huge heat loser, and you do not have enough warm air going in to offset the loss. Mimi split is probably your best option, since your existing house system might not handle a room with that high of a heat loss.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  10. #10
    I am trying to zero in on a solution here. I looked at the system board - it is a Comfortmaker C8MPN100F14B1. I do see markings for EAC but there appears to be no connector. Same is true for the CONT FAN next to it. I am assuming that this model did not have this option installed. I see a what I thinks is a relay right next to it with an open NC or NO. I am assuming this is a low voltage relay, but assuming it triggers when the furnace runs I might be able to do something with this? I put pictures below of what I am seeing. Thanks for the direction.

    http://postimage.org/image/c7ph2vhpf/
    http://postimage.org/image/ov9tt4m03/
    Attached Images Attached Images   

  11. #11
    Join Date
    Jan 2008
    Location
    Texas
    Posts
    1,676
    I have used pressure or sail switches. If their is poor return with door shut an additional return would probably help.

  12. #12
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,615
    perfect solution would be a ductless mini split
    We really need change now

  13. #13
    Thanks for all of the help. I agree that the mini split would be a good solution - albeit a lot more expensive than two duct fans! The room was done properly - insulated, etc. However, it is cold because it is on the outside wall of the house and has casement windows going from 18" above the floor to the ceiling on three walls. So there wasn't much room for insulation except around the bottom of the walls and in the ceiling. There is no return in the room - the closest return is in the next room. The room is mostly laid on a concrete slab although there is access underneath at one end of the room. Would adding a return make much of a difference?

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