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Unico system vs forced air

BrentBrent Member Posts: 81
I can't comment on many things about hi velocity systems but the comment about being more efficient got my attention. One knock on hi vel (besides the high price) is they are not more energy efficient. I've found it very difficult to find tables listing the seer and capacity ratings with different condensing units. However if you can find them you will see that you have to use a 12 seer outdoor unit to get 10 seer and you usually lose capacity. ie with a 3 ton condensing unit you get maybe 31,000 btu.
For new construction I personally don't see why you would go with hi vel. For less money you could get a variable speed blower and a true 12/13 seer.



  • Annie HallAnnie Hall Member Posts: 28
    Latest and greatest (sort of)?

    Our builder is not a fan of radiant heat (probably because he's never had it before) and, as you can tell from my posts, doesn't know much about it. He disapproves of my heating choice, and now wants me to explore something I've never heard of -- Unico heating, which, I gather is a sort of forced air system that uses smaller ducts and somehow eliminates the large air movement and accompanying drafty feeling. No one in the local area is familiar with it, so I am hoping I can get some knowledge about it from you...please!
  • ScottScott Member Posts: 5,884

    Unico is the brand name of a company that makes a type of air conditoning system. This is referred to as a high velocity or mini duct system. There are other companys that make this style of A/C system, Unico is one of the better know and the type that my company uses.

    A hot water coil can be added to this system so that one system does A/C and heating. This would need a boiler to provide the hot water for heating. It allows a greater amount of flexabilty as the system can do hot water heat, radiant, indirect hot water heaters, and is easier to zone , just to name a few.

    Many feel this type of A/C is preferable to a traditional ducted system as the design of air flow does not move a large volume of air but instead by " aspirating " air or blending the air in the room, the ocupants of the room would not "feel" the air moving and would be more comfortable.

    Also I believe the high velocity systems removes a higher amount of humidty and there for are more efficient.

    All that being said you will pay a premium for a systems like this. You will gain smaller duct work, less soffits and pipe chase to be built due to the size of the duct along with the benifits I mentioned above.

    I am sorry that your builder does not like Radiant. Maybe its time to remind him just who's house he is building ! Maybe let him know who's money is being spent here and what YOU would like to have in your home ! There is NO style of heating that is more comfortable than Radiant !

    I have a customer who has hot air in his home. When he did the addition to his kitchen we installed a radiant floor. He is now building a small home for his mother-in-law and told me he wants radiant heat because " I have never been more comfortable than in my new kitchen " !

    Hope all this helps and I am sure there are others on this site who can offer you more advice.


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  • Steve EbelsSteve Ebels Member Posts: 904
    I agree with Scott

    On all the points he made regarding the Unico heat/a-c system. I've installed more than a few and customers are happy with the results. I'd still opt for a radiant system ANY day in my own home.

    That being said, the point I agree the most with is ditching your builder. Maybe it's to late for that and he's already started the construction but..... Don't let him dictate to you what HE wants to put in YOUR house. Sorry, I just don't understand why the great majority of builders don't want to learn anything new. What you put in your house is your decision, your money, and therefore your choice, not his. If he isn't willing to accomodate your wishes or learn something new, I have to wonder if he's the "right" carpenter. Remember, that's all he is. Just the contractor that plays with wood. The guys that play with pipes, ducts and wires have just as much, if not more to do with how your house actually works and feels than he does.
  • BillBill Member Posts: 345
    Great reply Scott...(nm)

  • J MatthersJ Matthers Member Posts: 24

    I have radiant in the basement, garage, first and second floors. My ac is with unico. I was going to heat the third floor and the garage loft with unico but decided to go with radiant in those areas as well. Why? Becase it is the best way to heat. It is also more efficent than forced hot air.

    Steve is right about the GC. The walls, windows and doors are the easy parts when it comes to home building. To design and install efficent and reliable machanical systems is a real talent. I did both in my house and the machanicals were far more challanging.

    As for your other post, build a tight, well insulated house and put in a good, well balanced HRV or ERV. You don't need to "exchande air between rooms", you do need fresh air in your home to keep it healthy. The best way is to build it tight and change the air saving as much heat as possable with a HRV unit properly sized for all the things in the house that use air and produce moisture (including humans).
    Good luck

  • kfkf Member Posts: 118

    SEER ratings don't take things like T-Stat settings into consideration. Being able to keep someone comfortable at a higher thermostat setting, say 75 with Unico vs 72 with conventional, because of greater latent heat removal and less draft areas.

    Also, if you match any manufacturers 10 seer condenser with its appropriate evaporator you will find that you don't get the total nominal BTU's either. I know that the difference in these numbers is closer with conventional however, did you no that ASHRAE assumes a 20% - 25% duct loss with conventional ducted systems while Unico only looses less than 5%. So in a conventional ducted system, although the evaporator/condenser may be providing closer to the nominal BTU's, 20%-25% is ending up in your basement or attic and not in the conditioned space.

    I could write for another ten minutes just on the comfort difference alone.

  • SteveSteve Member Posts: 3
    cleaning unico evaporators

    What about future maintenance? Ever try to clean the evaporator on a unico a/h? The 5-7 pass coil is extremely difficult to remove debris from the middle areas. Yes, I agree that this would not be an issue if the homeowner maintained the system properly (changed the filter on a regular basis) but the truth is it doesn't happen. Out of sight, out of mind. They'll remember when the system doesn't keep up because the plugged filter has the condensor cycling on the freeze stat. Several complexes in our area have Unico systems from the early 80's and most suffer from this above stated problem. If space is not an issue, a radiant heat system with a conventional variable speed air handler would be where I'd put my money. Humdity removal 3 times more than standard blower systems with Trane/American Standard timed blower sequence (comfort R). Just my 2 cents worth. Good luck
  • clammyclammy Member Posts: 1,996
    stanard verses unico

    with all said and done all unico i've done where in all 100 year old houses where there no clsets or room for standard a/c and as for effecieny unico will only give you a 10 seer but they remove more humidity then standard because of less cfm across there multi pass coil all aside there great for old plaster houses as for conv a/c if done right with seperate supply and returns and large grills instead of stanard 8x8 and properly sized duct work and properly sized unit cost less and performs as well as a unico for less money then the register and muffler kits for unicos.i've seem a few bad unico install in places where you wonder what where they thinking every system has it's place unico for old house retro and standard a/c with the ducts and the rest done right a variable speed system is nice but it won't correct undersized tin and one big return
  • BrentBrent Member Posts: 81

    Do you have a link to ratings from unico or one of the other manufacturers that show the btu capacity and seer for different condensing units. It seems like that information is guarded closely. I could not be looking in the right place though. I would be surprised if the same person could have the setting 3° higher with a hi vel system. Maybe 1 or 2°.
    I agree with your statement on btu ratings. A typical matched 3 ton system might have 35,000 btu.
    I haven't seen the ashrae report about duct loss. A 20% loss might be likely in your standard tract home but not every duct system will have that loss. A quality installer can have leakage that matches a hi velocity system.
    I find it interesting that that the dept of energy is requiring a minimum of 12 seer starting Jan 2006. The hi velocity systems lobbied and are going to be exempt from that requirement.
    I am not against hi vel systems. I think they have their place in old homes. I don't see why someone would want one for new construction.

  • John MillsJohn Mills Member Posts: 221
    I'm with Brent

    Yes, the HV do suck some more moisture but take the same money or less and use a variable speed blower getting 13 SEER not 10 SEER and put a dehumidistat on it. Probably end up with similar indoor conditions but still getting high SEER.

    You can have leaky duct systems with either type. Anything HV around here is a Space Pak put in 30 years ago. Just as leaky as conventional ducting.
  • Dianeb126Dianeb126 Member Posts: 1
    Don't do UNICO

    We put in a Unico system 10 years ago.  Saw it on This Old House and said yea that would work great for us.  We always had issues with the unit freezing up and not shutting off.  The installer would come back replace the switch 4x.  We had them checked nothing wrong with them.  Added more holes to balance the system.  I finally got in touch with a rep to come out and look at the system.  It was leaking freon every year so that was why is was freezing up.  When I started looking more closely at the system I saw the installer had left openings and mice have gotten into the tubes that feed air out and in the return ducts.  For 3 years I tried to work with Unico to "Make it Right", they said they would send replacement tubes but we would have to pay for the labor.  They never sent the items that was last Aug 2012.  If mice can chew threw the mesh then rats would love it.  It can't be cleaned because the tubes are fiberglass.  It is going to cost 17,000 to rip it out and put a conventional system. (mice can't chew threw medal).  Oh did I mention we have a son that has had 2 heart transplants and they want me to run the system after what I have seen in the area?  I want people to be aware there is a BIG con to this system.
  • ZmanZman Member Posts: 3,517
    Sorry to hear...

    Sorry to hear about your Son's health.

    It is also unfortunate that your Unico system was installed so poorly.

    A house with a rodent problem is also unfortunate.

    It is unclear to me what this problem has to do with Unico.

    Many conventional systems use flex duct. The often have freezing and electrical problems when installed incorrectly.

    This site is awesome for helping people sort out heating problems. There are plenty of other sites that are designed to help consumers to rip on manufactures.

    Are you looking for assistance so you don't duplicate your past bad install or just looking for a 10 year old post to rip on?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • heatpro02920heatpro02920 Member Posts: 991
    Sounds like you had a bad installer

    I have installed my share of unico systems including multi zone heatpump/condensing systems with auxilary electric and hydronic coils.. They have their place, by all means when you can fit conventional duct work and a real air handler, do it, but some properties will not allow this with out major renovation, so this can be a less invasive install for a Forced air heating cooling system... They tend to be much louder, more expensive, and a trickier install but by no means are they all bad, when installed and designed properly they work very well, and can provide very comfortable indoor temperature control...

    But sadly, I think {or hope} the original poster already bought a system since this post is indeed 10 years old, he probably doesn't even own that property any more {the people that bought it after him may not have it anymore at this point, lol}. So you may not get the friendliest replys here to a post like this, we try to be positive and constructive vs what ever this is supposed to be... I know how you must feel after 10 years of problems, but do your self a favor and get a good tech in there to straighten it out once and for all, you may have to spend a few bucks but it will be worth it in the end....

    PS if there is a problem we can help you with by all means, post some pics, let us know what the issues are and we will put our heads together and get you on the rite track...
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