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  1. #1

    Hot Room Question

    I have a very small "hot" room (100 sq ft out of a 2400 sq ft house) that I am trying to control the climate via central AC/Heat Pump. It requires very little heating in the winter (but does require some), due to the amount of heat generating electronics in the room. It does require, however, quite a bit of AC in the summer to cool it. I think that I will be required to manually adjust the dampers each season to handle this situation. This will be a pain in the butt, but I see no way around it. Is this common? Other thoughts/comments?

  2. #2
    Join Date
    Oct 2003
    Location
    Cincinnati,Ohio
    Posts
    21
    What size ducts are running to this space? What is your return size? Can the space be cooled by adjusting the dampers?

  3. #3
    Join Date
    Oct 2006
    Location
    Vallejo, CA
    Posts
    154

    Lightbulb Return Air?

    Is there any return air duct to this room? If not, is it possible to install ducting to this area? If so, possibly increasing supply air ducting for this room and possibly remove damper for this room.

  4. #4
    Join Date
    Jan 2008
    Location
    Hells Kitchen, Phoenix Arizona
    Posts
    318
    If it gets too hot in the winter and not hot enough in the summer there isn't much you can do with that...You don't need as many CFM in heating as you do in cooling...I think a register with an OBD or a disc damper in the collar if its flex is the easiest solution...
    "Overkill is an often underrated achievement", Will Hayden -- Red Jacket Firearms

  5. #5
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    It might be best to install a window or portable air conditioner. Even if you increase airflow in the summer with a larger supply duct you still won't be satisfied. It'll be cooler while the AC is running. However, are you going to chill the entire home just to cool that one room? Do you want to run the single biggest appliance in the home to cool 100 square feet? On mild days you'll be doing exactly that. That one room will be hot, the rest won't, so you'll have to run the whole home AC to cool 1/24th of it.

    Spot heat loads are best served by spot cooling.

  6. #6
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,273

    Thumbs up Unique needs require special set-ups

    Quote Originally Posted by ivanl3 View Post
    I have a very small "hot" room (100 sq ft out of a 2400 sq ft house) that I am trying to control the climate via central AC/Heat Pump. It requires very little heating in the winter (but does require some), due to the amount of heat generating electronics in the room. It does require, however, quite a bit of AC in the summer to cool it. I think that I will be required to manually adjust the dampers each season to handle this situation.
    You may need ~ 200 CFM to cool a room with 1,500watts / 5,000 BTUh.
    More air flow would be required during periods with sun directly on the windows.

    200 CFM air flow would require an 8" duct with > 80 Sq inch diffuser or
    two 6" ducts.

    Add a 200 CFM bath exhaust fan with temperature (set-point ~ 77' F) and speed controls.
    The exhaust fan should be ducted to the air handler return.
    The air handler would not be operated until the house t-stat was calling for cooling.

    The exhaust fan would not operate in the winter with room temperature less than 76'F effectively reducing the air flow in the winter to this room with the door closed. A system air imbalance may be (slightly) noticable in this case.

    Page 19 -22 for quiet, large Broan bath fan.
    13 MB file: http://www.broan.com/Catalogs/Broan_Bath_Fans.pdf

    Unique needs would be met without additional heating and cooling capacity. This set-up is variable with speed and temperature controls to meet your specific needs.
    Last edited by dan sw fl; 02-24-2008 at 05:02 AM.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  7. #7
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    Even if the house was designed with that hot room in mind, and if you gave accurate specifications to the designer on how much heat the equipment would throw off, it would still be difficult to balance the system for both summer and winter.

    A band aid fix would be to turn your thermostat fan switch from auto to on. A better solution would be to install a ductless split system for that room only.

  8. #8
    Thanks for all the feedback. I am going to try manage the situation by adjusting the dampers each season and see where that gets me.

    I really did not want to introduce another coooling system (mini-split, window uit, etc) unless ABSOLUTELY necesarry. So I want to exahust all other options first. I am not there yet.

    The bath fan an is an interesting idea that I will consider, thanks.

    There is a return and a supply in the room. Supply duct is 8".

  9. #9
    Join Date
    Dec 2007
    Posts
    89
    what is this room used for?

  10. #10
    Just a home office, but I have the following heat generating equipemnt in it : LCD TV, LCD computer monitor, lap top computer, tower computer, fax maching, DTV recevier (HD) -- generates a lot of heat, 4 lamps, fax machine, speaker phone, printer, wireless router, cable modem, large window that gets lots of sunlight, low ceiling, VOIP modem, speakers and me. It also has a decent amount of furniture in it that takes up space.

    The room right next door to this room is the excat same size (and same window situation), but is a spare bedroom. The temp in that room (w/ no HVAC turned on in either one -- just the respective lights and elctronics) runs about 7 degrees lower.

  11. #11
    Join Date
    Nov 2007
    Location
    Washington State (on the Peninsula)
    Posts
    80
    If you are going to adjust dampers you could cause dammage or shorten the life of your system due to improper system airflow. You might concider having a zoning system put in so that the airflow through your system is maintained at proper levels.

  12. #12
    Quote Originally Posted by Dave-B View Post
    If you are going to adjust dampers you could cause dammage or shorten the life of your system due to improper system airflow. You might concider having a zoning system put in so that the airflow through your system is maintained at proper levels.
    If damper adjustments damage the system, why do dampers even exist? Keep in mind, I am tampering w/ a very small % of the overall system. This is one (small) supply of a system of 12 supplies (most of which are larger). I was tuaght that the purpose of the dampers was to make minor adjustments to CFM that don't warrant a change to the overall system design. Seems that is exactly the case here. AM I off base?

  13. #13
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,549
    For situations like this. We install what we call a "slave zone". It is a damper and thermostat which will not turn the unit on, but the stat opens and closes a damper only. You add a lot of air to counteract the heat from computers during the cooling season and the damper closes if no heat is needed in the room during the winter time. Duct modifications are definitely needed, but it works like a champ for situations just like this.

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