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I have a 1929, 1+1/2 story house that I’d like to have a mini-duct air conditioning system installed in. I’ve been looking at the Spacepak and Unico systems. I was wondering if anyone had any comments on those systems and/or if there were other systems I should be considering.
I was also wondering if these systems can have dehumidifiers installed with them like a traditional forced-air system has.
Finally, are any of these systems do-it-yourself systems? (and, by that, I am just referring to duct installations). If so, should that be done by the home owner or is it a good bet to hire an HVAC specialist for the installation of the duct work? I wouldn’t mind installing the duct-work myself over the winter, as we are also finishing the basement, and then just have the condensor/dehumidifier/fans of the system installed come spring by an HVAC specialist.
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Darrell, I am not familiar with the system you are talking about but, all air condionng systems are dehumdifiers. As warm moist air is passed over the evaporator coil it is cooled below the dew point( the point at witch water vapor will condense out of the air in simple terms). Free standing dehumdifiers are in fact small a/c compressors and evaporator coils. You don't get any sensible cooling from them because the condencer side that exhaust the heat is in the same cabinet with the evaporator. You will feel more comfortable because the relative humidity will be lower. One of the major problems in the HVAC buisness is over sizing units. To large an a/c unit will cool the air in a space before it has time to dehumidfy it. You end up with a cool, yet stuffy feeling living space that doesn't feel like it is actually cooled to the thermostat set point.
Hope this mini lesson helps a little.
Dave
*darrell, I wish the search function was working...we had a couple of extensive high-velocity AC threads a while ago.For the most part, there are three companies to look at:Unico, SpacePak, and Hi-V. Here's another Unico link with some partial on-line installation guides. Old links, I hope they're still active...Unico has great boxes...air handlers, etc. Their mini-ducts are pretty good, their "proprietary" trunk ducting is junk...fiberboard. If you use their fiberduct I'll come over with extra long tweezers to help you pull all the Unico fibers out of your family's lungs. Then I'll slap you silly.Spacepak has pretty good hardware. I think their mini-ducts are superior to Unico's, in that it's more of the twist-lock variety. Pretty easy to assemble.Unico and SpacePak are pretty close in price...Unico slightly more...it's more of a household word due to advertising and them shmoozing the boys on certain PBS television shows.Hi-V is kind of the DIYer of high velocity air conditioning. It's priced below the others, and for a reason. You'll essentially get a box full of parts and it's up to you to assemble the pieces into a functioning system. I'm embellishing some...but whereas Spacepak is twist-lock, and Unico is maybe screwing two pieces together, Hi-V is a jumble of parts. It's workable, it's just more labor intensive.Regardless of which system you use, you can assemble a useable setup.I'm more familiar with Unico and Spacepak literature/product, so these comments are directed towards them:Once you get an ACCURATE set of BTU numbers, the layout is fairly easy. There are certain rules that must never be violated. NEVER use a 2" mini-duct run shorter than 10' (or 12', depending on manufacturer). Shorter means too much noise from the airflow. While I'm on noise, it is the main criticism of these type of setups. Even a well-installed setup will be noisier than conventional. Yeah, it bcomes background noise after a while, but the unit kicking on at night can be startling. Many advise running the fan 24/7. You get so many BTU's of cooling with each full duct. If a room requires two "full" ducts (10 or 12' long is a "full" or "whole" duct) to cool it, sometimes it's better to instead use three "partial ducts." A "partial duct" is simply longer than the minimum required (10 or 12'), thus less efficient...as when ducts get longer than 10 or 12', you lose about 5% efficiency (or airflow/cooling capacity) for each additional foot of duct length. So, a 15' duct only provides 75% of the cooling airflow that a 10' duct supplies. The key is that three "partial" ducts pushing out less air per duct is quieter than two "full" ducts pushing out more air per duct...and with these sytems, noise control is tha name of the game.The literature has lots of tips on layouts...duct bends, etc.One other thing to keep in mind is that these systems are slightly less efficient, cooling-wise, when it comes to the condenser. I think each ton of condenser cooling is worth 10800 BTUs instead of the conventional 12000 BTUs. Sometimes that may require you to up the condenser size by a half-ton.No need to add dehumidification as Dave noted...these hi-velocity systems pull about 20-30% more moisture out of the air than conventional systems.If you're skilled, if you're relatively smart, if you can read and follow written instructions, you should be able to run the ductwork yourself. To get a quiet installation may require installing more product, thus spending more money. It's up to you how good of an installation you want.Also, realize Unico and Spacepak can cost about 30% more than conventional installations...if you can even find a supply house to sell to you. Your labor will offset much of that.Good luck!
*Dave:Thanks for clearing up the dehumidifier issue. That was something I probably should have figured out on my own. ;-)Mongo:Wow. Thanks for all the advice! I did a search for the Hi-V systems, but didn't find a web site. Do you know if they have one?i If you're skilled, if you;re smart, if you can read and follow written instructions, you should be able to run the ductwork yourself.Oh. Good. I'm all for doing the labor. My only concern was how much knowlege of the actual physics of the installation I'd need to know. It sounds like that go through all of the formulas for me, though.Do these systems all hook up to your standard out-door central air conditioning unit? (I assume they do).The noise is a good point to bring up. Though, admittedly, give me noise over 96 degree weather with a dew point of 70 anytime!Actually, I'll probably end up with a few runs pushing 50' anyways, so the multiple-ducts to one room will work well.Off hand, do you know if these ducts can be branched, or do you need to run individual ducts back to the main blower unit? In otherwords, can I run a 4" duct to the top floor and branch it into two 2"ers? I do realize that at 4" they probably aren't considered mini-ducts anymore.
*ERROR: My apologies...I just re-read and caught an error in my previous post. With Unico, you lose 2% for every foot the supply duct is over 10 feet. I wrote "5%."I did a search for the Hi-V systems, but didn't find a web site. Do you know if they have one? I included a Hi-V link in my post.My only concern was how much knowlege of the actual physics of the installation I'd need to know. It sounds like that go through all of the formulas for me, though. The books have rudimentary BTU calc charts. These calculations will lead you to how many outlets you need per room. Your supplier may offer to come out to your house, take measurements, and run the numbers for you. There are some pretty good directions on how to and how NOT to install the ducting.Do these systems all hook up to your standard out-door central air conditioning unit? (I assume they do). Yes.Actually, I'll probably end up with a few runs pushing 50' anyways, so the multiple-ducts to one room will work well. Remember, you lose 2% for each foot that the 2" supply duct exceeds 10 or 12 feet. A 50' duct would lose 50-10=40; 40 x 2%=80%; 100%-80%= 20%...not too efficient, and very expensive regarding that amount of dusting for that little amount of airflow.Off hand, do you know if these ducts can be branched, or do you need to run individual ducts back to the main blower unit? Take a closer look at the links I had on my first post. In general, you'll have a main trunk line (8-10" diameter or equivalent) coming out of your air handler. This is typically run in tha attic or basement. Your 2" ducting will branch off from this main trunk line and supply cooling air either through ceiling or floor vents in the living spaces. Each manufacturer has max duct length guidlelines...usually 20-25' maximum.Take a look through those links, see if they help you at all...
*Darrell, I have just finished the installation of my ac system retrofit. The house is a cape cod in NY. The house has hydronic heating and we did not plan on instaling ac when we built the house. One hot summer changed our minds on the whole ac idea. I researched the different systems and chose to go with Unico. Just had the compressor and evapoator installed two weeks ago and the system works beutifully. Very quiet cool and dry. Some things to cosider. I installed all of the duct work myself. Huge savings in labor. Must follow Unico's instructions precicely. I called Unico directly and "lead" them to believe that I was a large installer. This serves two purposes. First they will continue to talk to you and actually answer your questions. Second free stuff. I asked if they had some liturature and or traing videos to help train my "crew" (me, myself and I). Withing a couple of days the complete Unico system manual and a instalation training video came in the mail (no charge). This inoformation is invaluable weather or not you plan on doing the install. One problem I had was finding anyone locally that had experince with high velocity high pressure sytems. I ended up sending a cad drawing of my floor plan to the local consultant for Unico (two states away). He overlayed all the outlet location on the print and sent it back. First thing you need to do though is have the system sized by a credible AC installer. You need this information to plan the duct work and number of outlets. I recommend dowsizing slightly from the recommended size. Two reason are 1.) most installers oversize and 2.) there is a higher temp drop across the Unico's coils so it is more effective at removing latent heat (moisture). The house ends up with dryer air thus allowing you to keep the setpoint higher. I have my set at 75 and it somtimes feels chilly. I down sized from 3 ton two 2 ton. House = 1800 sqft. only shade on north end. The duct instalation was fairly easy but pretty time consuming. One word of caution. Ask the installer if he has experience with the type of system you choose. Mine said yes but the guy that showed up had never worked with these systems before. Subsequently I had to fix his mistakes, nothing to serious though.Good luck and stay cool.
*Mongo:My error. I was figuring the main duct into the run lengths. With the main duct running through the attic, the longest run shouldn't be any more that 15' - 20'Thanks for the links. I'm plowing through those sites this weekend. I do really wish one of them would reply to my emails, though. ;-)Boydman:Thanks for the first-hand experience. My brother is an architect, so maybe I can have him convince the companies to send the info his way. ;-)It hit 96 today. I think I'm already sold on the system!
*Mongo is the expert, and Boydman had some good things to say. This is my first summer with the Unico I've put in my own house. I don't know how much is just good luck, but I'd have to say that the air conditionig works just perfectly. Single system in a 2 story house- 74 degrees up, 74 down. Hot like hell outside. It pulls so much moisture out I'm going to have to finally figure out where to drain it to, its flooding the back patio now. Heat pump this past winter another story- froze my feet all winter except when big fire in fireplace, but my wife was comfortable. I still need to tweak a couple of my duct runs to quiet them down, but I seem to be the only one who really notices the loud ones. Unico wouldn't even sell me some clamps, had to get the HVAC cat to order them for me. I did all that duct work in a gutted house, can't imagine it being very easy when all the walls and ceilings are done.
*lonecat, I was thinking of emailing you and asking how the system was working. Glad to see that it all came together for you.Stay cool!Mongo
*Darrell-Do I remember from a previous thread that you are in MN? If so where...? In MN here too, just finished an install of a Unico in my own house, never done one before, turned out well. Agree with everything Mongo says except the noise. I've got a lot of info but way too much to get into here for my typing speed...-Brian
*Hi Brian. I'm in St. Paul.And, as you know, it's sill hitting the mid-90's with 70% humidty. Every house remodel project is on hold until I get that air conditioning unit installed! :-)Just a quick thanks to everyone who posted. I have literature coming from each of the three companies so hopefully I can start making some decisions in the next few weeks...Brian...do you install HVAC systems professionaly? If so, I'd be interested in talking with you. I'm leaning towards getting the duct work installed myself over the fall/winter, but I'm always for 'doing it right' vs. 'doing it myself' and am open to any advice you have. Oh, and I have one more small follow-up question. Can these systems have house-wide humidifiers hooked up to them for use in the dry winters? I'm guessing it may not be a good idea to pump moisture through these, but thought I'd ask.
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I have a 1929, 1+1/2 story house that I'd like to have a mini-duct air conditioning system installed in. I've been looking at the Spacepak and Unico systems. I was wondering if anyone had any comments on those systems and/or if there were other systems I should be considering.
I was also wondering if these systems can have dehumidifiers installed with them like a traditional forced-air system has.
Finally, are any of these systems do-it-yourself systems? (and, by that, I am just referring to duct installations). If so, should that be done by the home owner or is it a good bet to hire an HVAC specialist for the installation of the duct work? I wouldn't mind installing the duct-work myself over the winter, as we are also finishing the basement, and then just have the condensor/dehumidifier/fans of the system installed come spring by an HVAC specialist.