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  1. #14
    Join Date
    Jun 2008
    Posts
    10

    Confused

    Thanks, Mr. Bill. Unfortunately, I'm just a layman and have no clue what a VS air handler is. I'm in Jacksonville, Florida, about as humid as you can get. Pressurization isn't the main problem, of course, I guess it's a side effect of what's causing the problem, if I'm understanding everyone correctly. What a helpful bunch of people you are.

  2. #15
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,953
    Quote Originally Posted by bhe View Post
    Thanks, Mr. Bill. Unfortunately, I'm just a layman and have no clue what a VS air handler is.
    "variable speed" That means that the Air handler has a variable speed motor in it, most of these motors are able to overcome a lot of air duct issues that other fixed speed motors can't, by ramping up or down when needed, hope this helps.
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  3. #16
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by bhe View Post
    No go, Big Jon3475. I tried just looking for the Builder's Guide, but the links were to a place to purchase the Guide, not for info in the Guide.

    I guess I just need to find a good A/C technician. Unfortunately, the last one (that installed this system and it's ductwork) doesn't seem to know all there is to know, and referral from a layman is probably not going to be helpful. After all, our guy was really nice and honest and hard-working, but this issue requires more technical expertise than he had, apparently. Got a clue about how to find someone really knowledgeable?

    Thanks again.
    Try this;

    http://www.buildingscience.com/bsc/d...montgomery.htm

  4. #17
    Join Date
    Jun 2008
    Posts
    10
    Thanks, dash and Mr. Bill. This is good information. Perhaps I can do a little more research on this and then (hopefully) find a good A/C guy that understands this stuff and can apply it to our situation. Any certifications or something like that to look for when trying to find someone?

  5. #18
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,913
    Quote Originally Posted by bhe View Post
    Beenthere, yes, those bedrooms have trouble cooling when the doors are closed. You have to turn the thermostat down at least 3 degrees for that room to be as cool as the living area when the door is closed, and the living area then gets too cold, of course. The return air on the main bedroom, with the pressurization problem, is not too small - it's about 10X20.

    Thanks SO much.
    The grille may be 10 x 20, but what size is the duct thats hooked to it.
    In order for that room to pressurize, the supplies must be putting more air into the room then the return can take out.
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  6. #19
    Join Date
    Aug 2006
    Location
    Marco Island, Fl
    Posts
    729
    Please do a simple experiment before you have more grills and jumpers cut in, although proper air return and pressure equalization is essential to good operation.

    You see, you are not saying the rooms don't cool, just the hallway and living areas are cooler when the bedrooms are at their desired temperatures.

    Prop the doors in question open from the door frame the width of a shoe.

    Let them run for a day or so. If that solves your problem, jumpers and such may help.

    If the rooms are still hot, it may be a simple thermostat location issue.

    In new homes, and especially Master bedrooms, windows are prevalent. If the bedrooms rooms faces north east to northwest, a thermostat in the hall may not trigger on....especially with the doors closed. Hallways are generally toward the interior of the home, and bedrooms generally on the outer part of the home with external walls and windows. I find many times air from the other zones keep the thermostat off and satisfy it early. The living area part of the zone in question, may be getting help staying cool from other zones.

    Zone systems should try to be set up where similar loads are grouped together so this does not happen.
    Once the thermostat can sense the load properly, airflow can be balanced.

  7. #20
    Join Date
    Dec 2005
    Location
    San Jose, CA
    Posts
    465
    move the thermostat to the bedroom

  8. #21
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,913
    Quote Originally Posted by davo View Post

    You see, you are not saying the rooms don't cool, just the hallway and living areas are cooler when the bedrooms are at their desired temperatures.
    From the original post.
    The thermostats are all in a hall area, which seemed like a good idea at the time of install. However, what happens is that when a bedroom door is closed, it'll get too hot because the thermostat is not in that room.

    She also said that they get cool if the door is left open.
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  9. #22
    Join Date
    Aug 2006
    Location
    Marco Island, Fl
    Posts
    729
    Yes she did, but with the doors open, sometimes the natural movement of air will allow the t-stat to pick up the heat.

    With the doors closed, there is no natural air movement.

  10. #23
    Join Date
    Mar 2008
    Location
    Houston, Texas
    Posts
    352
    With the system on and the door closed ( standing outside of the door, ) place your hand at the bottom of the door. If you have a strong flow of air coming from that gap, under the door, you more than likely need a return in that room. There is a good chance that you are supplying a large amount of air to the room and it is having problems getting back to the system.

    If that is the case, your hot room is affecting the performance of the entire system.

    Undercut the door to increase the gap or add a return inside the bedroom.

  11. #24
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,913
    Quote Originally Posted by davo View Post
    Yes she did, but with the doors open, sometimes the natural movement of air will allow the t-stat to pick up the heat.

    With the doors closed, there is no natural air movement.

    And since at least one room is pressurizing when the door closes, its a lack of return for at least that room.
    Good chance if one bedroom is low on return, the others are also.
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  12. #25
    Join Date
    Aug 2006
    Location
    Marco Island, Fl
    Posts
    729
    Quote Originally Posted by beenthere View Post
    And since at least one room is pressurizing when the door closes, its a lack of return for at least that room.
    Good chance if one bedroom is low on return, the others are also.

    As I said in the beginning of the first post, proper air return is vital to comfort and proper operation.

    I have had many contractors try and solve poor thermostat location problems with returns to no avail.
    If the thermostat cannot sense the load, how can it keep a separate room with a lot of load comfortable?

  13. #26
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,913
    Not many houses have a thermostat in the bedroom. But many of them are keeping the bedrooms comfortable, without sensing the actual load in those bedrooms.

    If those bedrooms are getting the air flow they need(supply and return) they will heat or cool at the same rate as the rest of the house. A person sleeping doesn't add that much heat to the room to make it gain heat that much faster then the stat location to count.

    Once the sun is down, there is no solar gain to make a bedroom a higher load then the stat location.
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