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  1. #1
    Join Date
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    4H: Hot, Humid Houston H.O.
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    I would like to clarify how a ventilating dehumidifier such as the Aprilaire 1700 works (probably similar questions, answers for Thermastor too). I understand the 1700 to be cheaper to buy and less efficient to run, than the Thermastor -- that's an OK tradeoff in some situations. I also understand the 1700 has a somewhat better control system.

    Is the 1700 designed to ventilate whenever the AC runs? The furnace? My thought here is that it might over-ventilate in the peak summer conditions if something does not reduce the intake of outside air. Or are the Aprilaire designers way ahead of me?

    With recent weather not calling for cooling in humid S.Texas, I am just possibly selling myself on adding such a device. It's a whole set of reasons, not least of which is ventilating with that fresh air intake. Although I own a Santa Fe Rx stand-alone, I am just about enthusiastic enough to have a "do again" type of purchase.

    Thanks very much -- Pstu

  2. #2
    are we talkin air comfort or air control? if its air comfort i just open the windows when its nice outside. if its air control (like preserving objects that could become damaged) then again why bring in fresh air? it just makes the thing work harder! unless you have high occupancy, gas make up, exhaust make up, etc.

  3. #3
    put simply, What are we tryin to do here? does the structure have concerns or past issues/tendencies? specific reason to control humidity? specific reason for fresh air? sooooo many choices and methods to address specifics... humid basement? even a lil portable may be an appropriate and cost effective method...

  4. #4
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    no I don't think so

    >>are we talkin air comfort or air control?

    You need to define your terms just a little clearer. I myself am comfortable when the air is dry and it smells/feels like outdoors. I live in a semi-rural neighborhood so air pollution is not the same problem it is for most city folk. I live in S.Texas which has a near-tropical climate so humidity is a problem more often than not.

    >>if its air comfort i just open the windows when its nice outside.

    Where are you from Kmills? Can you tell me what is the humidity in your house? Do you watch such a thing?

    Opening a window "when it's nice" may work for you but the number of hours that is true in S.Texas is strictly limited. This is basically a hot climate and the air carries humidity in proportion to temperature. When the thermometer is in the range of 60-65 I can usually do what you do -- any higher and the humidity is unacceptably high. There are occasionally days when the temperature is 65-75 and the humidity is low. There are NOT a lot of hours when either condition applies in this climate.

    >>if its air control (like preserving objects that could become damaged) then again why bring in fresh air?

    Again *you* know what you are thinking but I am not understanding you. You clearly want to ignore ASHRAE standards for ventilation do you not? A lot of people ignore it from a basis of ignorance, but do you have any clear and coherent arguments why it's OK to do that?

    Regards -- Pstu


    P.S. This thread was intended to be about some specific questions about 1 or 2 specific products. If you really want to discuss basic questions such as "why do you ask" then I can converse about that. Hopefully for your benefit.
    But I sincerely hope that sooner or later a product-knowledgeable person will see this thread and point to some answers about how the actual product works.

    [Edited by pstu on 03-08-2006 at 12:54 PM]

  5. #5
    im sure S. Texas and SE Florida have pretty similar climates and humidity throughout the year. humidity that gets handled by tightly sealed homes and the AC unit. is there a reason you need additional dehumidification? and if im ignoring ASHRAE standards, then i am not alone. been in SE Florida doing AC work for 14 years (res and commercial construction, service and install) put in literally thousands of units of all sorts and have YET to even see a dehumidifier OR fresh air in a residential application around here...dont get me wrong though fresh air is a nice concept you reduce negative pressure, ventilate stale air, BUT at the cost of ADDITIONAL moisture in the home that makes your air conditioner work even harder.... new fan/speed controls on existing equipment and the new variable speed A/Hs deal with the issue of humidity very nicely.

    just in doubt about you needing one at all...

    oh let me clarify air comfort and air control
    air comfort = gee it feels nice in here
    air comfort = gee it feels nice but its clammy humid too
    air control = my picasso i paid big $$ for is gonna be ruined if i dont keep the humidity at %50
    hope that clears things up

  6. #6
    Join Date
    Jun 2004
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    4H: Hot, Humid Houston H.O.
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    Alien to one another

    Kmills, the answer is AIR COMFORT. In additon I am providing myself a safety margin to minimize the likelihood of ever having a mold problem. I would call that AIR CONTROL too. Actually I hate having to justify myself to someone who is unqualified to help with my project -- having lived in a hot-humid environment for 14 years and never having seen a residential dehumidifier, nor residential fresh air system, I would never call that qualified for *this* project.

    I am beginning to regret saying I would be willing to converse on this subject with you. It seems more and more clear that you are inclined to deny that this is even a valid concern. I disagree and it is my perogative to choose what to do in my home. Also I believe that my steps are very well respectful of the best ideas in Building Science. Maybe not best practices, but I try to get closer with each step.

    So you are content with the hot-humid climate in Florida. I asked if you know the humidity in your house and you ignored the question. By contrast, I own 6 meters to test humidity in various parts of my house. I read them all the time. That just appears to prove how different we are in wants and expectations. I have benefitted from the Thermastor Santa Fe Rx dehumidifier for a couple of years now, you cannot tell me it's not helping me. For me it is time to consider how I might do the similar task, but better. It is my firm opinion that I want mechanical ventilation, and I think that using a ventilating *dehumidifier* is a definitive answer to the problem of latent load from that air.

    If you would read the general direction of what Teddy Bear and Carnak say, you would have a much better understanding of my perspective. I don't really have much enthusiasm for going through every little part of past discussions all over again.

    I am stubborn about knowing what I want. If you are stubborn about it not making sense to you, then we would be best off agreeing to disagree.







    Regards -- Pstu

    [Edited by pstu on 03-08-2006 at 11:56 PM]

  7. #7
    http://www.energystar.gov/ia/new_hom...20Builders.pdf

    try this. ASHRAE 62.2 was developed without doing a cost study of any detail. no wonder states aren't in a rush to make it part of their mechanical code.

  8. #8
    Join Date
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    Please stop hijacking this thread

    Dude, you are hijacking this thread!!! If you want to have a different thread titled "Questioning the need for ASHRAE ventilation", I think that's a much better idea than educating you and me here!

    If indeed somebody evolved ASHRAE standards without cost study THAT IS IRRELEVANT TO ME. I have seen excellent cost studies. I will offer to show them to you ON ANOTHER THREAD. My project is for my house, not yours. For you to persistently insist on this thread that I am a fool for wanting mechanical ventilation and humidity control, is somewhat less than good manners.

    As of now my offer to discuss your subject, is valid only on a new thread with a different title. Do you like the title I suggested above? You should have the honor of choosing the thread title, as all discussion has been according to your agenda.

    Good day sir -- Pstu



    [Edited by pstu on 03-09-2006 at 08:10 AM]

  9. #9
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,261
    Originally posted by pstu
    I would like to clarify how a ventilating dehumidifier I also understand the 1700 has a somewhat better control system.

    Is the 1700 designed to ventilate whenever the AC runs? The furnace? My thought here is that it might over-ventilate in the peak summer conditions if something does not reduce the intake of outside air. Or are the Aprilaire designers way ahead of me?
    With recent weather not calling for cooling in humid S.Texas, I am just possibly selling myself on adding such a device. It's a whole set of reasons, not least of which is ventilating with that fresh air intake. Although I own a Santa Fe Rx stand-alone, I am just about enthusiastic enough to have a "do again" type of purchase.
    Thanks very much -- Pstu
    There is a little life in the "Indoor Air Quality" forum yet. My hat is off to both kmills &Pstu. Most of us "old timers" have come down the road that kmills is on. It's the "why do need this new stuff for anyway" road. I was at the spot where kmills is now about in 1984. I depended on a 3 ton heat pump for humidity control. I finished my basement which became musty in about a year. My wife and kids started with puffy eyes and allergys occasionally. As I investigated the problems found mold in damp corners of my basement and dust mites in our beds. After a residential dehumidifier and tweaking the heatpump trying for <50%RH but unable, used a commercial 100 pint dehumidifier. This fixed all the problems. No allergies, dust mites, or must odors and a vary comfortable home. My people are not sensitive to these problems or do not care about the better comfort levels. So we all try get along.
    But to the original post. I hoped an Aprilaire(AP) supporter would explain their control. AP suggest connecting the supply/return to the airhandler(AH). Also suggest operating the AH when ever the AP operates. Optional fresh air connected to the AH instead of the AP. AP ventilation timer is with 30 min, 1 hour, 2 hour, or 3 hour cycle. You select 1-60 minutes per cycle of AH fan/open fresh air damper open. The selected cycle is repeated throughout the day. Other controls and connections can be used.
    Ultra-Aire"(UA) suggest fresh air connected to the UA direct along side the a return from the home. The adjusted blend of air is filtered and blown into the supply side of your AH. UA control options include remote a low voltage dehumidistat and fan control as basic. When the UA fan is "on" or dehumidifying, fresh and house air is distributed throughout the home. Most use the digital ventilation timer option which is adjusted to provide a life stlye schedule providing fresh air ventilation when your are routinely in your home. This includes various schedules and a electric fresh air damper. In addition to the standard merv 11, various filter upgrades including merv 14/activated are available. UA is available in several capacities. A new AP competive unit with better eff. is also being introduced Ultra-Aire 90H. AP is much farther down the road than kmills but still a ways behind UA. TB (Trying to stay ahead of a slowly building croud)


  10. #10
    Join Date
    Apr 2002
    Posts
    11,808
    Lead story in the current ASHRAE IAQ newsletter, "Over Ventilating in Hot Humid Climates".
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #11
    Join Date
    Apr 2002
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    Teddy check email when you get a chance
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  12. #12
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    Jun 2004
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    details

    Thanks Teddy Bear, for that very helpful specific information. Would you mind if I asked some detail questions? I would very much like to because I am at the stage of window shopping, just prior to making a project and writing a check to pay for it.

    Has Thermastor told anyone a release date or estimate, for their newer model? Does it cut features in order to be more strongly price competitive?

    If you would like my uninvited opinion, it looks to me Thermastor needs a version redesign, to make their product less expensive to factory build. When I bought my Santa Fe Rx, there was a wheel broken in shipping and I had the experience of disassembling it enough to replace the castor. What I saw looked like fine craftsmanship, but many discrete parts where with American industry I am used to seeing fewer and more specialized parts. It looked rather more like a prototype. I am sure it does not affect operation except some pieces are fiendishly hard to access if/when repairs are needed. But I said to myself "if some company makes one with the same specs but for mass production, they could really bring the cost down". IMO Thermastor is uncomfortably close to being hand built and vulnerable to competition from a company with deep enough pockets to build a more efficient assembly line. I would hate to see Thermastor suffer from competition but my business schooling tells me it might, regardless of the fine design and technical excellence.

    I'd like to continue pestering you with questions if you have the time, for example is even air distribution the primary reason one would connect a whole-house dehumidifier to the supply plenum? My observations are two: 1) the dehu blower must overcome a serious pressure in that plenum, possibly 0.5 inch w.g.(see postscript below),
    and 2) BSC (Lstiburek's Building Sciences Corp) in a 2002 paper titled "Conditioning Air in the Humid South" apparently connected one this way, and at the end of the study recommended a different configuration. They recommended that *not* connecting to the supply but rather a dedicated vent into a room, would improve dehumidification performance. Evidently BSC believes there are performance issues, which I interpret this way: the dehu might push air over a wet coil, and compromise the humidity removal.

    If one is easily amused, it is a little bit funny to see Lstiburek and company try one specific design feature, then after an experiment recommend something completely different. That's the scientific method for you. It reveals just how much this exalted guru is guessing -- at least he tests his theories.

    Best wishes -- Pstu

    P.S. Second thoughts a day later: that 0.5 figure will seldom apply. I was thinking of one particular configuration, where the dehu pulls air from a return plenum and pushes it into the supply plenum. The dehu blower will be working against the total ESP of the central air handler, minus the pressure drop of the coil. With some homes such as mine the ESP has been measured around 0.7 inch w.g. (improved since then). It would seem this air resistance is serious enough to consult the fan table for the dehu blower, for the usual reasons of adequate air flow (in doubt I think) and fan electric usage (minor issue I think).

    [Edited by pstu on 03-12-2006 at 11:06 AM]

  13. #13
    Join Date
    Jul 2005
    Location
    Orange County, NY
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    936
    Originally posted by Carnak
    Lead story in the current ASHRAE IAQ newsletter, "Over Ventilating in Hot Humid Climates".
    Like I always said “Demand Ventilation” is the new way of thinking.


    Core

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