Help reviewing 3 Unico HV AC proposals ...
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  1. #1
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    Feb 2008
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    Help reviewing 3 Unico HV AC proposals ...

    ... to add AC only for a small 2 bedroom slab-on-grade home which has radiant in-floor heat. Upper Midwest, 1 mi. from a Great Lake. Main house is 890 SF: Living/Dining combined and Kitchen face east, Kitchen is on southeast corner; on the west side, the Bedrooms flank one Bath and central Hallway/Attic access. Utility room 130 SF is attached on south, access door from Kitchen is often closed. Garage attached on south side of Utility. Large east windows at Living and Dining and Utility. I understand load calculations need to be done abstractly, however seasonal canvas awnings limit solar gain on Living, Dining, and Kitchen. House is clad in stone, together with the concrete slab it tends to provide a stable environment. Attic insulation is original mineral wool plus 3 1/2" batt for total ~6", some additional batts around eaves; exterior walls 3 1/2" batts; windows mostly original single-pane with new wood storms. Attic storage space is important use. Corner lot, condensing unit must be on southwest corner of garage. Condensate drain line must go to laundry standpipe in Utility.
    I am not seeking traditional system proposals, I've focused on Unico, I have three proposals, I'd appreciate comments before I seek some clarifications from some of the proposers, I'll identify them as $, $$, and $$$. I only have direct experience (positive) w/$$$, all three are mentioned as reputable by local Unico distributor. So ...
    - Size unit: $ 1.5T; $$ 2.5T; $$$ 2.0T. (I have not yet asked $ to double-check his load calc; $$ states he had a Unico engineer double-check the load calc; $$$ recommended not including Utility outlet to keep unit from being 2.5T.)
    - SEER: $ states 13; $$ did not note; $$$ states 13.
    - Air handler placement: $ and $$ south end of Attic near Utility; $$$ central area of Attic.
    - Return: $ Kitchen; $$ and $$$ central Hallway.
    - # Supply outlets: $ 12; $$ 17; $$$ 14 ($$$ no outlets in Utility).
    - Condensing unit: $ Carrier; $$ Amana; $$$ Armstrong.
    - Supply plenum: $ and $$ Gustafson pre-insulated metal; $$$ "sheet metal w/ ext. ins."
    Any comments on any of these details or additional thoughts are appreciated, thanks.

  2. #2
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    Quote Originally Posted by 1634j View Post
    ... to add AC only for a small 2 bedroom slab-on-grade home which has radiant in-floor heat. Upper Midwest, 1 mi. from a Great Lake. Main house is 890 SF:

    Condensate drain line must go to laundry standpipe in Utility.

    I am not seeking traditional system proposals,

    ... or additional thoughts are appreciated, thanks.
    Use a multi-split heat pump

    http://www.mrslim.com/Products/subCa...CategoryID=151
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
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    [QUOTE=1634j;- Size unit: $ 1.5T; $$ 2.5T; $$$ 2.0T. (I have not yet asked $ to double-check his load calc; $$ states he had a Unico engineer double-check the load calc; $$$ recommended not including Utility outlet to keep unit from being 2.5T.)[/Quote]

    I wouldn't use a "Professional Company" that can't do its own load calcs. Anyone in the busines seriously should have either the long form manually or software to do the load calc. If they don't have something to calculate the HV ducts, that's not quite so bad but if they're quoting Unico, they should have the software to do the whole calc. We don't recommend HV systems but we do have the software to do the load calcs if needed.

    - SEER: $ states 13; $$ did not note; $$$ states 13.
    You won't get 13-SEER on an HV system. The HV manufacturers had to get a waiver on the 13-SEER minimum just to stay in business. You'll get a 13-SEER condenser because that's the minimum efficiency available but you'll be lucky to get 11.5-SEER actually.

    - Air handler placement: $ and $$ south end of Attic near Utility; $$$ central area of Attic.
    My preference is to go nearest the center when able. That helps to even the static pressure losses and aids in balancing the system more easily.

    - Return: $ Kitchen; $$ and $$$ central Hallway.
    Return in a kitchen??? Not legal in our state. I can't speak for yours but I certainly would look askance at a company recommending a return air be installed in the kitchen.


    - # Supply outlets: $ 12; $$ 17; $$$ 14 ($$$ no outlets in Utility).
    The number of supply outlets varies with the tonnage of the system. 7-outlets per ton of AC is the current recommended number, up from 5/ton when the systems first came out. All to diminish noise complaints.
    - Condensing unit: $ Carrier; $$ Amana; $$$ Armstrong.
    The manufacturer of the equipment is not nearly as important as the company installing. Get recommendations either written or verbal from satisfield clients. Ask what job went badly and call the client to see how well it was handled.

    - Supply plenum: $ and $$ Gustafson pre-insulated metal; $$$ "sheet metal w/ ext. ins."
    I don't like interanl insualtion. Health issues over the long term. I'd recommend having an externally insulated duct system throughout.

    I don't know why you don't want a conventional system. They're quieter and when properly installed will take up certainly not more and possibly less space than the HV system. Just the number of run-outs from the HV system will infringe on your space. A properly installed conventional system can be suspended with the ducts run high, leaving plenty of storage space. You might consider reputable companies that do conventioal systems. You might be pleasantly surprised at the costs and the outcome.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  4. #4
    Join Date
    Apr 2004
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    420
    Quote Originally Posted by 1634j View Post
    ... to add AC only for a small 2 bedroom slab-on-grade home which has radiant in-floor heat. Upper Midwest, 1 mi. from a Great Lake. Main house is 890 SF: Living/Dining combined and Kitchen face east, Kitchen is on southeast corner; on the west side, the Bedrooms flank one Bath and central Hallway/Attic access. Utility room 130 SF is attached on south, access door from Kitchen is often closed. Garage attached on south side of Utility. Large east windows at Living and Dining and Utility. I understand load calculations need to be done abstractly, however seasonal canvas awnings limit solar gain on Living, Dining, and Kitchen. House is clad in stone, together with the concrete slab it tends to provide a stable environment. Attic insulation is original mineral wool plus 3 1/2" batt for total ~6", some additional batts around eaves; exterior walls 3 1/2" batts; windows mostly original single-pane with new wood storms. Attic storage space is important use. Corner lot, condensing unit must be on southwest corner of garage. Condensate drain line must go to laundry standpipe in Utility.
    I am not seeking traditional system proposals, I've focused on Unico, I have three proposals, I'd appreciate comments before I seek some clarifications from some of the proposers, I'll identify them as $, $$, and $$$. I only have direct experience (positive) w/$$$, all three are mentioned as reputable by local Unico distributor. So ...

    - Size unit: $ 1.5T; $$ 2.5T; $$$ 2.0T. (I have not yet asked $ to double-check his load calc; $$ states he had a Unico engineer double-check the load calc; $$$ recommended not including Utility outlet to keep unit from being 2.5T.)
    The different sizes is a red flag. Off the cuff, 2.5 sounds way too high, but then again, get the load calcs in hand for review, even if they won't leave you with a copy, ask them to go over them with you in person. Unico is premium stuff and pricey. Check references from previous SDHV installations of all.
    - SEER: $ states 13; $$ did not note; $$$ states 13.
    SEER rating suffers a bit with Unico. You'll usually end up somewhere around 11. However, due to lower duct losses and a drier overall indoor ambient because of the 30 degree delta across the coil, overall net efficiencies can actually increase. The theory being that the drier the home, the higher you can set the thermostat at while remaining comfortable. Oversize the system however, and you'll be miserable (with less money in your pocket then you would've spend on a conventional system to boot).

    - Air handler placement: $ and $$ south end of Attic near Utility; $$$ central area of Attic.
    The layout of ductwork is slightly different with SDHV systems then with conventional. Unico pushes a "horseshoe" shaped plenum or "perimeter" loop as the most desirable supply plenum styles. Either of these methods requires the air handler to be placed in the center of the attic. Having the return in the center of the house would keep thing nice and balanced too, so I have to say the third co. has it right. Take that with a grain of salt though, as I haven't seen the attic myself.
    - Return: $ Kitchen; $$ and $$$ central Hallway.
    Center hallway over the kitchen anyday
    - # Supply outlets: $ 12; $$ 17; $$$ 14 ($$$ no outlets in Utility).
    These vary due to the varying sizes. A minimum of 6 per ton--assuming each supply duct is not longer than 10', is Unico's suggestion. More is better IMHO, all else being equal.
    - Condensing unit: $ Carrier; $$ Amana; $$$ Armstrong.
    If it were me, I'd match with the condensing unit containing a scroll compressor with the longest warranties. Any can be used with Unico.
    - Supply plenum: $ and $$ Gustafson pre-insulated metal; $$$ "sheet metal w/ ext. ins."Incredible attention must be paid to sealing all seams and takeoffs really well. Use the greatest R-value you can afford, don't compress the insulation if exterior.
    Any comments on any of these details or additional thoughts are appreciated, thanks.
    Answers above...
    Get the sizing right and most of the other stuff will fall into place. We have installed more than a dozen Unico systems. They are awesome systems, nearly invisible and utterly quiet and I sometimes wish we could go Unico only. FWIW, I wasn't sold on Unico before I installed my first one, and have heard all the downsides relating to efficiency, noise and whatever else. Can now say, have it installed by the book and you'll be very happy.

  5. #5
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    May 2000
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    Indianapolis, IN, USA
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    Here's what high velocity does to you

    Since you mention Armstrong, take a nice 4SCU13LE136 which would get a nice 36,000 BTU 13 SEER on a matching Armstrong fan coil or 14 SEER with a variable speed air handler.

    With the Unico, the SEER is 11.00 and the capacity is down to 28,600.

    The "2 ton" outdoor unit gives under 1.5 tons of cooling.

    So just remember you are killing SEER and capacity with your Unico and spending a lot more than you have to for it.

  6. #6
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    Lancaster PA
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    If there's room in the attic for a conventional. then go conventional.
    You can have a conventional VS blower for about the same money as a HV blower.

    Return in kitchen, Is against national code.
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  7. #7
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    Jan 2004
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    Location: Tulsa Oklahoma
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    Talking

    We have installed several Unico systems and for your application they would work great. I would imagine that you would be dealing with high humidities in
    the area where you live so the Unico is going to work wonders removing the humidity from inside your home. You need to be sure that your installers are Certified by Unico. If you get Certified installers Unico will give the equipment
    a 5 year parts warranty. Contact Unico directly if you can't get the answers
    you need they are very friendly up there.
    Whoa Maynard - that's not how it works.

  8. #8
    Join Date
    Feb 2008
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    20
    Thanks for all the comments so far, very helpful. More from me ...

    Other systems - I have heard and read pros/cons about Unico HV, it's a bit hard to sort out for this layman. I am focusing on HV because dehumidification and finished appearance are very important to me. I have let the 3 contractors know that if they wished to quote conventional also I would be open to reviewing such an option: none have. I may still ask another contractor if they might be interested in quoting conventional, I would tell them this is in the context of 3 quotes I already have for Unico. I looked at Mr. Slim and similar and do not like the appearance.

    Load calculations - Each contractor did their own field measuring and calculations, $$ just mentioned he had a Unico engineer double-check to confirm. I am very concerned that I not buy more capacity than is really needed, either now (some tree shading, use of awnings, window treatment control) or future owner (perhaps less trees, may not use awnings or window treatment wisely). I believe this house is a bit unusual with the masonry mass, south side buffer zones of Garage and Utility, the interior temperature environment stays more stable than other homes I have lived in.

    SEER - I should have clarified the SEER quotes I have received are related to the condensing unit. I am hopeful that my actual operation of the system on peak demand days will not be 72 degrees, I expect I'll be pleased at ~75 *if* dehumidification is very efficient.

    Air handler placement - The main house Attic inside dimensions are about 36' N to S by 23' E to W, the gable roof ridgeline runs N to S, there is just under 6' clearance from the underside of the ridgeline. If the air handler is placed at the south end (as $ and $$ proposed), it would be at about the center of a 'U' of two plenum arms running from S to N under the E and W slopes of the roof. Contractor $$$ proposed central air handler placement near a central hall return, he would install one central plenum under the roof ridgeline.

    Return - The Kitchen return proposal bothers me, I need a clarification from him and I'll probably contact our village inspector also. Seems like a generally unwise practice, but for a very small house it may not practically be a big deal. "BeenThere" could you please cite a "national code" reference that disallows this so I can review with the contractor?

    Plenum insulation - I have little information on the Gustafson pre-insulated, but I don't think it's interior, one phrase from the literature I have is a spec mention: "The spiral pipe is pre-insulated with R8 eight foot section on a six foot pile giving the contractor enough insulation to wrap the fitting."

    Unico certification - $ noted Unico trained certification in his proposal, the other two did not list, but I can seek clarification.

    Thanks again for any and all comments.

  9. #9
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    From the International Residencial Code

    M1602.2 Prohibited sourses.
    4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, or other dewelling.
    5. A room or space containing a fuel burning appliance where such room or space serves as the sole sourse of return.
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