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Community and Q&A

Has anyone had experience with the Unico small duct system?

Andrew Bennett | Posted in Mechanicals on

I was looking at the top finishers for the department of energy’s “Race to Zero Student Design Competition” ( http://energy.gov/eere/buildings/2015-results ) and found the winner used the Unico system. http://www.unicosystem.com/the-system/how-it-works/air-handlers/. I recall actually being in a home in Chattanooga once 15+ yrs ago that I believe had one of these systems, but I really know nothing about them. With the problems associated with finding small enough systems for well insulated homes and cost effective systems…does anyone know if I should be looking at this as an alternative? Is it efficient? Is it cost effective? Bueller…Bueller…Bueller?

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Andrew,
    The only advantage of these systems is that they have small diameter ductwork that is easier to snake through the framing cavities of older buildings than conventional ductwork.

    Unico air conditioners are less efficient, not more efficient, than ductless minisplits or ducted minisplits.

  2. Andrew Bennett | | #2

    Mr Holladay, you know a good bit more than me about all this stuff, but I'm thinking that if the winner of that competition used this system it can't be too inefficient. There's gotta be more there than small ducts.

  3. Andrew Bennett | | #3

    So, I think I figured out part of it. Unicorn now has a mini-split system...so that'should part of the answer, but the design used in the competition also uses an air handler. So there's something else going on as well.

  4. Scott Intagliata | | #4

    Andrew, thanks for your interest. I am one of the owners, as well as the Marketing Director for Unico. Our products are very efficient, and they are also able to achieve, and have been documented to achieve, zero thermal loss and zero air leakage. Our product has been successfully used in over 100 LEED Platinum projects. And now, with our iSeries Multi Split line, you can achieve rated performances of between 16.5 and 20 SEER. I would strongly encourage you to visit our site for the Green market, http://www.unicosystemgreen.com. Also, please feel free to contact me directly at [email protected]. We offer free design services and have a lot of experience in the sort of projects you may be interested in. Thanks.

    1. Burninate | | #32

      Scott,

      "zero thermal loss and zero air leakage"

      I understand that you may have a marketing background? But when someone says these words to me about a physical system, they are a major red flag. There are few absolute zeroes in the physical world, and in thermodynamics they're actually against the law. If you honestly think it has zero air leakage that means you've never bothered or aren't capable of setting up something sensitive enough to test what the air leakage rates are. If you honestly think it has zero 'thermal loss' you don't understand what the word means. The right way to report near-zero figures for these topics to engineers is to measure them being fairly close to zero, put it in a white paper with the precise methodology (methodology defines what you actually technically mean when you say these things in summary), put it on your website, and quote the precise numbers, or at least the threshold for your measurement error.

  5. Scott Intagliata | | #5

    Mr. Holladay, I have read your blog on a number of occasions and find it interesting and thought provoking. I would very much like to connect you with other principals at our firm who could bring you up to date on our product and our progress in incorporating it into new, energy efficient structures with great success. Please give me some dates and times when you could be available for a Skype call or web conference and we will have a good chat with you. I think you will find it well worth your time. Thanks, Scott Intagliata [email protected]

  6. User avatar GBA Editor
    Martin Holladay | | #6

    Andrew,
    If you use a powerful fan to overcome the considerable static pressure of undersized (3-inch-diameter) ducts, you can still deliver the air that would normally be delivered by a smaller fan through generously sized ducts. But the decision to use a powerful fan and tiny ducts exacts an energy penalty.

    That's why Unico has tried to use litigation to argue that it should be exempted from minimum energy efficiency standards. See this legal brief: The brief begins, "This Decision and Order considers Applications for Exception filed by SpacePak and Unico, Inc. (Unico), seeking exception relief from the provisions of in C.F.R. Part 430, pertaining to energy conservation standards for central air conditioners and heat pumps (Air Conditioner Standards). SpacePak and Unico are manufacturers of small duct, high velocity (SDHV) air conditioning equipment. In their exception requests, SpacePak and Unico assert that they will suffer a serious hardship and an unfair distribution of burdens if forced to comply with the 13 SEER energy efficiency standard."

    Similarly, the company wrote a letter to Energy Star, complaining that the company finds it difficult to meet Energy Star standards -- and that Energy Star should therefore carve out a special category for companies like Unico that use small-diameter ducts: "The SDHV [small-duct high-velocity] minimum efficiency is near the maximum technology for this product class. We propose that the Energy Star specification for SDHV products include requirements that go beyond SEER and HSPF. Other criteria including quality installation, duct design, and system commissioning are equally important to the overall efficiency of the product class and should be included."

  7. Andrew Bennett | | #7

    This reminds me of when I was working on my masters degree. I had a job in a running store in Louisville, KY. Consumer Reports had some shoe rankings that were published. None of us could make any sense of their rating methodology. Then I worked for Whirlpool and even though we knew dryers used a lot of energy there were no Energy Star ratings for them. There are all sorts of rankings and certifications that need examination. I've read on quite a few websites, including this one, about the importance of well sealed ducts and commisioning a HVAC system. All that to say, I still don't know much more about this system than I did this morning, but...taking, "other criteria including quality installation, duct design, and system commisioning" into account may actually make some sense. You shouldn't necessarily be such a curmudgeon...course somtimes, sometimes we need a curmudgeon. Let's give them a chance to explain and see if we need one or not,

  8. User avatar GBA Editor
    Martin Holladay | | #8

    Andrew,
    Unico systems are great for certain applications, and if you want one, by all means install one.

    It's hard to defeat the laws of physics, however. Undersized duct systems are a nationwide problem. ECM blowers overcome these problems easily, by ramping up the fan speed to overcome high static pressure. You get the air delivered where it belongs, of course -- but the energy penalty is real.

    The difference in efficiency between ductless minisplits (which have a higher efficiency) and ducted minisplits is due entirely to the fact that ducted minisplits have a duct system. You can't move air through ducts without using energy. The smaller the diameter of the duct, the more energy you need to deliver the air where you want it to go.

    That said, Unico systems are a great solution for certain problems, especially retrofits.

  9. Andrew Bater | | #9

    Andrew, I have a Unico system in my new SIP/ICF home. For heat we have radiant tubing embedded in concrete on the ground and first floors, panel radiators in a couple second floor locations. The Unico system is utilized only for air-conditioning via a chilled water feed from the geo system buffer tank.

    For me Unico (or SpacePak) was a necessity, my wife considers seeing any evidence of mechanical equipment as evidence of poor design. Unico's small mains and ducts allowed us to run in areas where larger and yes probably more efficient ducts would have required soffits. Our home is extremely tight (about .9 ACH), has a cold roof etc, so our cooling system run times are short and that inefficiency isn't of much worry.

    Works great for us. (I didn't answer your question about "cost effective", but refer to my note about keeping my wife happy...)

    Andy

  10. Andrew Bennett | | #10

    I'll be interested to see how Mr. Intagliata responds. One of the things that intrigues me is how the handle bringing fresh air into the house. Their literature indicates that one can often due without a separate HRV or ERV which would (possibly) lower the overall initial cost of the whole HVAC system. IF their system brings in enough fresh air and IF it is priced right that could be an advantage on the front end. That's two IF's I don't have an answer to. As far as the fan goes, I would think (and I really don't know...just trying to reason through the system till he posts some answers) the fan ..big or small...is tyically a fairly efficient part of the system. As opposed to say the piston in a car engine or older compressor that accelerates, decelerates, changes direction, and then does it again a fan motor is always going in the same direction.

    So a fan, generally speaking isn't going to be horribly inefficient. Now, if the work of that fan is constrained by the small diameter of duct either the fan has to work harder or there will simply be less air blown through the duct. Their website indicates the use a lower volume of air. For filtration with an 11 MERV filter I would think that would be a substantial drag on any fan motor (I'm sure "drag" is not the proper term here, but I'm not an HVAC guy so I'm just gonna use the term drag). Could a ducted mini-split handle filtration like that over the long haul? What do people use for air filtration with mini-splits?

    The other issue with non-ducted mini's is getting the air to all the rooms. From case studies I've read on this site and the phius site some people are content to sleep in colder rooms and bundle up while indoors. As per Mr Bater above...my wife is NOT going to be putting up with that. If I told her I was going to build a super insulated house, but she would have to sleep in cold rooms or wear sweaters she would aske me what I've been smoking.

    To get air distribution done right (right being defined as where all rooms are comfortable...which is in and of itself a matter of perception) I haven't read of a solution the doesn't involve ducts or a mini head unit in each room. A minisplit head in each room woukd get a little pricey I think.

    With our last house built with SIPS we had a traditional 2 stage 16 SEER heat pump using flex duct. Though we used open web floor trusses and had all ductwork inside the heated/cooled cavity of the house we still had air distribution problems. Because of solid support beams (LVL's) that flex duct had a lot of up and over and under...bends and stuff. So my home office was sometimes warm in summer and cold in winter... As well as one of the rooms upstairs. If we had trouble with those issues with a ducted system I can only imagine they would have been worse with an unducted min-split.

    Returning to the topic of the Unico system with the small diameter ducts. It does remind me of something else from when I worked for Whirlpool Corp. That is the Jenn-air downdraft ventilation system with their cooking products. It had lower CFM's than many/must high powered high end hoods but worked better. Part of the reason was proximity...it was closer to the cooking surface. However, I remember it was a pressurized system. The number one complaint when the systems didn't work was generally fixed with the proper installation of the doodad (another techinical term to be sure) that helped the pressure build up. Could there be something in this system that works better for air distribution because of the latent pressure in a small duct? Again, I don't know, but I hope the reply from Mr Intagliata is able to address that.

    The system looks like it works WITH a mini-split. So you have an efficient compressor. You have a pressurized duct work system that (hopefully) gets air to the right places. It brings (supposedly anyway) in fresh filtered air so you don't need a separate HRV. Is there an efficiency price that goes with all that? Propably. Is it a big price? No idea. What's the up front price for one of the octopus lookin' thingy's vs a traditional or house full O mini's? Again, no idea. Let's see what the company rep cooks up for us.

  11. Greg Sutor | | #11

    As an HVAC contractor who stumbled upon this website I was pleased to see a thread with information about The Unico System. Even better to have a post listed from one of the principals at Unico to help explain their newest high efficiency product, the iSeries line. Our HVAC company has installed many Unico systems over the past 20 years as a solution for applications with challenging design parameters. It is commonly requested by architects for LEED projects or other high efficient home applications. The iSeries product they now offer is truly unique in its ability to combine the best features of mini-splits and small duct systems with authentic high efficiency ratings.

    It was disturbing to read the narrow minded and technically incorrect posting by Mr. Holladay. To state matter of factly that the only advantage of a Unico System is its smaller diameter ductwork completely ignores the issues of humidity removal and proper air distribution that it excels in addressing. Mr. Intagliata responded respectfully with a brief explanation of the features and benefits that Mr. Holladay was clearly not aware of, along with a personal invitation to learn more directly from the source. Mr Holladay didn't see it fit to respond to Mr. Intagliata directly, but instead chose to present evidence to Andrew that Unico Systems are inherently inefficient.

    As I mentioned I am new to the Green Building Advisor website, but I did read the impressive biography of Mr. Holladay, who appears to have extensive experience in many areas of green building. That makes it all the more surprising that he would comment so definitively on a product that he knows so little about. His statements about the amount of energy required to deliver air at different velocities may be true on the surface, but it pays no attention to the realities of efficiently delivering conditioned air in real world situations. Lower velocity air delivery systems may use less energy in some applications, but they also may not be able to deliver the air properly to the areas that require it. It's just not that simple.

    Unico ducts are not undersized, they are matched to the air delivery system that they are designed to work with. If Mr. Holladay took the time to read ACCA manuals on designing proper air distribution systems, he would understand that determining if a duct is undersized is not based solely on its size. Noise level, air distribution and energy consumption all play into this equation. Static pressure that is unacceptable in one system may be perfectly suitable in another. The efficiency and comfort that an air delivery system provides to the living space it serves is based on overall system design, not simply the size of a duct.

    Unico Systems are not trying to overcome the laws of physics, they are a good energy efficient solution for the right application. Mr. Holladay provided the example of a wall mounted ductless mini-split versus a ducted mini-split. It is true that the ducted model would use more energy to deliver the conditioned air through a duct, but why? In many cases you would find that the ductless model is not capable of properly delivering air to all the areas that need it. It uses less energy but it may not be able to achieve its intended goal.

    If ductless units were the recommended option for that type of application, it may be necessary to install multiple wall mounted units in remote locations to achieve proper comfort. So which system uses more energy, one ducted mini-split or three wall mounted ductless units? It's not that simple of an answer anymore. Let's not forget about aesthetics either. Surface mounted supply grilles as part of a ducted system are going to be quite a bit more inconspicuous than three wall mounted ductless mini-splits. In that same vein, the soffit needed to cover 3" Unico ducts is much smaller than what would be necessary with a typical 6" duct used in a conventional low velocity system. Maybe we should consider that another point of view that suggests low velocity ducts are oversized. Some applications are perfect for SDHV systems like Unico, which is why they are used in so many LEED projects.

    I certainly understand why Mr. Intagliata would choose not to respond to the biased postings Mr. Holiday made. He is more interested in proving that Unico products are inherently inefficient than learning about how they really work. That is very disappointing considering that he is a senior editor for this website. I don't work for Unico or any other SDHV manufacturer, I just use their products and don't like to see people being mislead to believe that they are something less than what I know they are. We have had great luck with Unico products over the years, it's a great equipment option for the right application.

  12. User avatar GBA Editor
    Martin Holladay | | #12

    Greg,
    Thanks for your comments.

    First, I'd like to stipulate that I believe that high-velocity Unico systems work. They deliver cold air to the places they need to, and customers with these systems are generally satisfied.

    The question under discussion is whether these systems use the same amount of energy as more conventional systems, or more energy.

    There are two striking features to your comments:

    1. You have provided no data relevant to the issue at hand.

    2. You haven't even proposed a mechanism to explain a phenomenon which, on its face, defies the laws of physics.

    A good example of data would be a study of two similar (or identical) houses in the same climate, one equipped with a conventional forced air system, properly designed and commissioned, and the other equipped with a Unico system. A year of energy monitoring data would be revealing. Ideally, the study would be performed by a third-party lab.

    The second issue concerns the question of the fan energy required to send large volumes of air through small diameter ducts. The laws of physics tell us that the energy required to do that is more than the energy required to send the same volume of air through generously sized ducts. If you want to champion a counterintuitive proposition that appears to defy the laws of physics, then (absent any data to support your proposition) you should at least propose a mechanism to explain it.

    Greg, I have an open mind. I just remain unconvinced.

  13. Greg Sutor | | #13

    Martin, I'm not sure what you mean when you say that I don't provide any data on the issue at hand. As far as I see there is no specific application data available. Andrew asked a general question about anyone who had experience with Unico's small duct system. You chose to compare the Unico systems efficiency level with a ductless or ducted mini-split, and made the blanket statement that it is less efficient.

    I would ask where is your data to back that up. Are you comparing it to a high static or low static mini-split ducted system? What manufacturer? What size system? And what Unico system are you comparing it to?

    If you were comparing Unico's new iSeries equipment you would have to start with the fact that they offer the ability to combine a ducted high velocity air handler with a wall mounted mini split. They both connect to a single inverter driven outdoor unit, something that no other manufacturer offers. Unico offers their own wall mounted mini splits with the iSeries, so in one example you could be comparing the efficiency of a mini split to a mini split.

    If you compare the energy use of a Unico iSeries high velocity air handler with a low static mini-split air handler (like Mitsubishi or one of many other manufacturer's) the Unico will of course use more energy for air delivery. That is because it is capable of over 1.5" of static pressure versus a typical maximum of less than .1" for low static mini split air handlers.

    In the real world that means that the maximum supply ductwork length is only 3' to 10' for a low static mini-split, versus well over 100' for a Unico air handler. It's an apples to oranges comparison you proposed. It's like saying that a moped has a better MPG rating than a hybrid Camry, and therefore a hybrid Camry is an inefficient vehicle. Let me know how that moped works out for you when you need to deliver 3 kids to school every day and pick up groceries on the way back. You might have to defy the laws of physics to make it happen.

    So let's take your example of two identical homes in the same climate, one with a conventional low velocity forced air system, and the other a base model Unico high velocity system. Both would be connected to an identical standard efficiency outdoor condensing unit. We can assume neither system has variable speed motors or multi stage capability, as I would assume you would want to use Unico's highest energy consumption models as an example to prove that it's not efficient.

    So assuming proper design and system commissioning, the conventional system will have greater duct loss to start with, because of the standard materials that are typically used on those systems. So already the Unico gets points for having more efficient duct work (another reason why it is why it used frequently on LEED projects).

    Next we approach cooling efficiency which can be assessed by each system's SEER rating as listed by AHRI. A typical base model conventional low velocity ducted system may have a SEER rating of 13, and the base model Unico with the same outdoor condensing unit may be 12 SEER.

    So it appears the Unico is just less efficient and proves your point. But wait a minute, that year of energy monitoring data you mentioned might be very helpful in this case. Which region are these homes located?

    In a high heat and low humidity zone in Arizona the conventional system may have saved considerably on utility costs while performing very well in every aspect. In a high humidity area like Florida we may find that the home with Unico System was able to keep the indoor temperature set point 2 to 4 degrees higher than the conventional system because of its increased ability to remove humidity. The conventional system in Florida at a lower set point may have used the same amount or even more energy than the Unico System to achieve the same level of comfort.

    If we choose to ignore indoor humidity levels and compare these systems only at identical indoor temperature set points, then maybe we should look past the 3rd party lab and ask our inhabitants about their comfort level. The Unico System typically removes 30% more humidity than a conventional system, which greatly effects the overall results. Imagine comparing a swamp cooler to mini-split. When properly designed they both can cool a space to 75 degrees, but one system removes humidity while the other adds it. Latent heat removal cannot be ignored when properly designing an HVAC system.

    Now let's move our comparison to Chicago. This climate zone requires about 700 cooling hours per year on average, and experiences high humidity conditions during the summer months. If we again choose to ignore comfort and perform a test based on identical indoor temperature settings, we can look specifically at how much more energy the Unico System will use.

    A 30,000 BTU system at 13 SEER would consume about 2.3 KW per hour (30,000 BTUs divided by 13 SEER = approx 2300 Watts divided by 1000 = 2.3 KW). At 700 cooling hours per year we are looking at 1610 KW annually. At $0.15 per KW the conventional system would have an annual operating cost of about $240.00.

    When we do the math on the Unico we will get an approximate annual operating cost of $263.00 (30,000 divided by 12= 2500 divided by 1000 = 2.5 times 700 = 1750 times 0.15 = 263). So at identical indoor set points you will save a whopping $23 per year with the conventional system (I think I paid more than that for an extra gigabyte of data on my smart phone this month). If you make the study require that each system maintain an equal indoor humidity level, that small savings would either reduce or completely disappear for the conventional system.

    You mentioned that Unico can be a good choice for retrofits because of its small duct work that can fit with less disruption, which is the most common application we use it in. The environmental impact of cutting open walls and ceilings to fit large conventional ducts would in many cases counter the small increase in energy costs that could be incurred by a base model Unico System. Using high efficiency iSeries equipment would result in a system that exceeds the SEER rating of many low velocity conventional alternatives. The aesthetic and historical preservation issues that Unico solves cannot be ignored either, that's why they used Unico equipment in the White House for its retrofit application.

    Have I mentioned low ambient heating capability yet? The iSeries heat pump can produce heat at outdoor ambient temperatures as low as -25 degrees Fahrenheit. When you have an application where natural gas and propane are not available or practical, these heat pumps could save hundreds of dollars each year in energy costs against the alternative of electric resistive heat.
    It's not even necessary to use an air handler, you could connect to multiple wall mounted Unico mini splits only and achieve exceptionally high SEER ratings.

    Again I do not work for Unico or any other SDHV manufacturer, I'm just a contractor that uses their equipment on a regular basis and knows from experience that they are not inefficient systems. Their company has made huge investments in the research and development of high efficiency products for high velocity applications worldwide. I have met Scott Intagliata on several occasions and I know that his decades of experience with The Unico system greatly exceeds my knowledge of their products. I would recommend you take him up on his offer to speak in more detail about their new products, as they may be a perfect fit for some of the high efficiency homes that you and your members deal with.

  14. User avatar GBA Editor
    Martin Holladay | | #14

    Greg,
    You have conceded that the energy required to send high-velocity air through small diameter ducts is more than the energy required to send low-velocity air through larger ducts. That was my point.

    If someone wants to buy a Unico system because they want to install small diameter ducts, they should. In most cases, however, other types of equipment -- including especially either a ductless minisplit of a ducted minisplit -- make more sense.

  15. Greg Sutor | | #15

    Martin,
    I did not have to concede that a high velocity fan requires more energy than a low velocity fan to move air because neither I nor anyone else contributing to this thread ever tried to claim that.

    What I took exception to is your statements:

    "the only advantage of these systems is that they have smaller diameter duct work"
    So latent heat removal, duct loss and air delivery methods must not have any place in your assessments of HVAC systems

    "Unico air conditioners are less efficient, not more efficient, than ductless or ducted mini splits"
    Beyond the fact that I've given examples of where the opposite is true, this statement ignores that Unico air conditioners in many configurations ARE ductless or ducted mini splits. Are you trying to say that Unico air conditioners are less efficient than themselves?

    "you can still deliver the air that would normally be delivered by a smaller fan through generously sized ducts."
    And then again no, there are countless situations, many that I am sure you have personally experienced where that is just absolutely false. Generously sized ducts don't fit in every application anymore than ductless mini splits being the solution for every problem.

    I understand that you don't want to concede to the bias and lack of evidence to back up your statements, but having an open mind may not be the best way to describe yourself. It would seem that as a senior advisor to this website your time would not be best spent recommending against using products that you're not fully educated on, especially ones that have already been used in many applications as high efficiency solutions for green home building.

  16. Andrew Bennett | | #16

    Mr. Sutor,

    Can you explain to me how the system meets the ASHRAE 62.2 standard. The literature says it is the only system that is third party certified to meet that standard. I don't understand that. Does it just have a damper door that lets in some air and is then tempered as it' make's it's way though the "octopus duct" (that's my own technical derived term for the ductwork). Also, the literature claims up to 30% better dehumidification. These two claims can be verified it makes the system much more attractive as I don't have to have a separate HRV or ERV and no separate dehumidifier. However, I"ve not located anything on the websites or literature that tells me the mechanism of how these things are accomplished.

  17. Greg Sutor | | #17

    Andrew,

    One of the ways Unico achieves increased humidity removal is with a much colder evaporator coil. Typical ducted low velocity systems have a temperature drop of approximately 15 to 20 degrees Fahrenheit (the temperature difference between the return air going in to the system and the air conditioned supply air going out). Unico high velocity air handlers average a 25 to 30 degree temperature drop. When room temperature air hits the colder evaporator coil, the larger delta results in more humidity being removed while the air is cooled. 50% cooler discharge air and 30% more humidity removal as an average.

    The other way that Unico or any other cooling system achieves better humidity removal is with longer cooling cycles. The 30% number for average increased humidity removal is based on both systems being single stage equipment, but there are other options available for multi stage operation.

    With a Unico Green Series air handler you can connect a conventional 2 stage condensing unit (Carrier, Trane, or one of many other manufacturers). With the iSeries you use their high velocity handlers, wall mounted mini splits or a combination of both. Instead of using a different manufacturer's outdoor unit, they developed their own. It uses Inverter technology that controls the compressor speed to modulate refrigerant flow. This is the same technology used in most mini split units.

    By using multi stage or modulating compressors, the cooling cycle runs much longer, resulting in better humidity removal. The only time the system removes humidity is when the compressor is running, so the longer it runs the more humidity it will remove.

    Again, this is true for any cooling system, not just Unico. But even when comparing a conventional ducted system to a Unico high velocity ducted system, and even when both use inverter technology for modulating refrigerant flow, the Unico will still usually have better dehumidification ability because of its colder coil temperature.

    As far as the ASHRAE 62.2 standard, I honestly don't know the answer to that question. I do talk with Unico's technical support team on a regular basis and I will make sure to ask about it the next time I do.

    By the way, their product support is stellar. Some large manufacturers are better than others in this area, but none of them compare to the responsiveness of Unico. They are a family run company and its just a different experience from our end dealing with them. We can get answers for our more complex applications straight from the engineers who help design the equipment. Even better, they are also more than willing to talk to consumers directly about their products.

    I'll post again when I get an answer to your question.

  18. Greg Sutor | | #18

    Andrew,

    I did talk to some people at Unico recently and found out a little about the feature you mentioned. The Unico Green Series air handler has a programmable control board on the air handler that includes a set of contacts that can control a damper connected to an outdoor air intake. The damper and the duct work must be field supplied, this feature just provides a way to control it.

    The idea is that you program it specifically for your application to open the damper for the minimum required time to satisfy the ASHRAE 62.2 standard (non-continuous ventilation). This damper could be connected to a duct supplying outdoor air directly, but in many climates I would think you'd need an ERV or HRV to avoid condensation during extreme temperatures. This relay can also control the HRV/ERV.

    As far as I know they have only included this feature on their Green Series air handlers, not their standard air handlers or the iSeries air handlers. The Green Series air handlers are used along with conventional unitary manufacturer's air conditioners or heat pumps (Trane, Carrier, etc.), using either single stage or two stage compressors, but not inverters.

    I also just read that Honeywell has incorporated a similar feature into some of its thermostats, but I do not know which models specifically. They call it a built in ventilation controller for satisfying 62.2 that includes temperature and humidity lockouts.

    As I understand it they are both basically timers for a relay that with the right programming input will limit outdoor air intake (whether direct or through an ERV/HRV) to the minimum amount required to achieve the 62.2 standard for non-continuous ventilation (or more if that's what you want). Hope that helps.

  19. Andrew Bennett | | #19

    Thanks for the answer Greg. I think were the Unico system could have an advantage over normal duct systems is this feature, but the devil is in the details. Looking at most install photos of Unico there is a lot of duct. It may be small in diameter, but there's a lot of it. The air spends a good deal of time in the plenum and then the supply tubing before being exhausted. IF (and that is an I-F...if) the conditioned air is less humid than a normal system because their coil runs cooler and the make-up air to coming in through the damper is spending a long enough time in the plenum, being blended in with conditioned air, it could very well have less of a need for a ERV or HRV. This is really the only kind of scenario I can see where the Unico system becomes more cost effective both short term and long term. The cost of running ductwork for a ERV/HRV in addition to the regular HVAC ductwork is added expense with any solution. My understanding is that Unico installs are typically higher ($) than "conventional" (who on this site really uses anything conventional) systems. So if the Unico system does NOT require the addition of an HRV/ERV then I would think the costs come back into line. One think I am thinking of is if I frame my floor with 2x product instead of open web trusses or I joists and I could have some savings there. However, that creates a requirement for bulkheads to run ducts...at least in some areas. With the Unico perhaps I could realize some cost savings by framing with 2x, not having a separate ERV/HRV, and still be aesthetically pleasing with lower profile bulkheads (that might not end up being obtrusive at all if I can put them in a closet or something. Or....it could be 6 of one and half a dozen of another. There are a lot of ways to get from point "A" to point "B." Point "B" in this case is a cost effective solution to be energy efficient AND comfortable WITH good indoor air quality.

  20. User avatar GBA Editor
    Martin Holladay | | #20

    Greg,
    The feature you describe (one that controls a motorized damper in an outdoor air duct) is part of a central-fan-integrated supply ventilation system. For a thorough description of this type of ventilation system, see Designing a Good Ventilation System.

    The described control offered on some Unico equipment substitutes for a FanCycler control (also known as an AirCycler control).

    The important point here is that any ventilation system designer needs to choose between several options when selecting a ventilation system. A central-fan-integrated supply ventilation system is one option; an HRV is another; and an ERV is a third.

    But once you have chosen your ventilation system, you're done. You don't need two ventilation systems. If you have decided to install a central-fan-integrated supply ventilation system, you don't have to rush out and buy an HRV.

    Similarly, if you want to install an HRV, go ahead. But if you do that, you don't need to connect an outdoor air duct to your Unico.

  21. Andrew Bennett | | #21

    Okay...so that is the answer to my assumption that you don't need the HRV or an ERV if you have that feature. What I don't know is if the cost differential evens out (separate conventional system and ERV or HRV complete with separate ductwork) vs Unico. My guess is that is going to be a case by case design issue that the two part system could win sometimes and the Unico could win sometimes.

  22. Andrew Bennett | | #22

    So...from an April Post to some final September answers. Luckily, my whole project has gone sideways and I am all the way back at the design stage instead of having my house built at this point as was the original plan.

  23. User avatar GBA Editor
    Martin Holladay | | #23

    Andrew,
    If you like the idea of a central-fan-integrated supply ventilation system, you aren't limited to Unico equipment.

    These ventilation systems are installed every day (quite inexpensively) on ordinary forced air systems (central air conditioners with air handlers, or furnaces, or both).

  24. Andrew Bennett | | #24

    My experience has been that the typical "open the damper door" solution to ventilation does lead to humidity issues because there is very little tempering or blending of the humid outdoor air and the conditioned air. Is there a way to address that issue in ordinary systems without an HRV/ERV? If so then that really is probably what I am looking for as I am on a tight budget.

  25. User avatar GBA Editor
    Martin Holladay | | #25

    Andrew,
    In hot, humid weather, all ventilation systems will add moisture to the indoor air. The best way to limit this problem is to make sure that your ventilation system is adjusted to provide the smallest acceptable volume of ventilation air.

    The problem of an "open damper door" ventilation system sounds like a central-fan-integrated supply ventilation system that was poorly designed -- one where the installer forgot to include an AirCycler control and a motorized damper. (It's also possible that the installer failed to commission the system, and the system is adjusted to over-ventilate.)

    If adjusting the ventilation rate isn't enough to solve your problem (and I'm assuming we're talking about an air conditioned house that uses the air conditioner to lower the indoor relative humidity), you could consider installing an ERV. ERVs also introduce humidity into a house when they ventilate during hot, humid weather, but they add a little less humidity to the house than other ventilation systems.

    Finally, if all else fails, you may need to install a dehumidifier.

  26. Andrew Bennett | | #26

    Thank you to both Martin and Greg for helping me understand these systems and options.

  27. bugofclutter | | #27

    In the event that anyone is lurking on this forum looking for advice, we have had this system in our home for about 1o years and just recently found that ALL the tubing has disintegrated. It was showed to Unico who denied any responsibility and instead claimed that the tubing was "exposed" to something. Hmmmm. Really? An entire house. Moisture was suggested. Hmmmmm, like our entire house had an interior rainstorm repeatedly for 10 years?. I'd seriously recommend against using this system if the manufacturer can't make tubing that lasts more than 10 years. See the attached photo. We have to replace ALL the runs in our home.

  28. FluxCapacitor | | #28

    Awful. Sounds like a $$$ repair.

  29. bugofclutter | | #29

    Thanks, yes. By the time we're done, we'll be halfway to a brand new system again. The tubes were sent back to Unico via the supplier, to have them examine, but Unico refused to see them or examine them. Just looked at photos and denied responsibility and put the blame on the tubes having been "exposed" to "something". We're just disappointed in the manufacturer's product and response. This is not an inexpensive system to install.

    1. Lance Peters | | #30

      WOW! Thanks for sharing!!! I'm going to post a related question as to not hijack this thread focused on Unico.

  30. luceyda | | #31

    It appears that our Unico high velocity system installed 9 yrs ago for $32k by Innovative Air has leaked out all of its coolant. We have serviced it annually on contract and changed the filters regularly. We had to spend $3k to replace the evaporator coil 2 years ago after it leaked out and dripped through the ceiling. Innovative says it may be the best option to replace everything for $12k. It was great while it worked, but I'm concerned that Unico's product may be a lemon to be in this situation such a short time after installation. Advice appreciated!

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