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  1. #1
    Join Date
    Aug 2009
    Posts
    154

    Is there any way to have an efficient high velocity system?

    Is there a spacepak or unico system that can provide high energy efficiency? Everything i read seems to say that i will only get about 11 seer with high velocity which sucks. I see spacepak now makes something called an air space with an ec motor... Is this something better?

    Also, would my current 2 stage Lennox xc21 4 ton unit be compatible with a hv system? I have not found any info on using 2 stage ac units with high velocity systems.



    I am planning an addition and have so many challenges with running large ductwork that it almost makes it impossible.

  2. #2
    Join Date
    Nov 2011
    Location
    Central Va.
    Posts
    1,043
    We do not install Unico though we have taken classes, so my advice would be to talk to a local company that not only installs this type of system, but might have jobs they have done documented for you to look at. I was actually impressed with a few of the features and am keeping this system as a "ace in the hole" for that job that I cannot get traditional ducting into (still waiting...lol).

    If there is a local R.E. Michel, contact them and they should be able to give references for the local companies that install this product.

    Just as a side question, Tom, what are the "challenges" you face on the project?

  3. #3
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,698
    High velosity systems are expensive but there is a place for them. I've installed quite a few when nothing else would work. They work great and are very quiet, which doesn't make sense for "high-velosity".

    Now there are more and more "mini-splits available if you don't mind having a "box" on the wall. They do make ducted models, but it sounds like you have a room issue.

    Regarding efficiency........I would say half the "hi-eff. systems are not achieving the SEER they are rated for. At least the high velosity system will dehumidify better than most and thus you can keep a higher stat setting.

    I have seen people install a new "hi-eff." A/C and need to lower the stat 6-7 degrees to have the same comfort as before. Is that efficiency?

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Exclamation

    Efficiency and High Velocity and mutually EXCLUSIVE !

    1st Option - Mini-split
    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

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,292
    +1 for the mini split.

  6. #6
    Join Date
    Aug 2009
    Posts
    154
    The challenges I face... My house is a split level and only has a partial basement. In addition many of the floor ceiling joists change direction making duct runs near impossible (unless i move the system to the attic) Perfect example, one of my kids bedroom is 10x12 and has (2) 6" ducts while another 10x12 bedroom in my house only has (1) 5" duct. Not good and no way to get the proper ducts to certain rooms if i keep the system in my partial basement -- especially when we add an addition. I considered the mini split but don't like the wall units, plus I have to figure out heating. I don't think the ductless heat pumps can work on the coldest NJ days.

    I think I am going to keep my Lennox G71v furnace and xc21 ac unit (which are top notch products) and move it to the attic. The pro is that I could have much better duct runs without a million turns. If i had a full basement then i would be in a better situation, but i dont. The con is that the ductwork and equipment will have to endure attic temp swings (NJ climate). While attic hvac systems are not the best choice, I think I am going to have to go with it. Use r8 insulation and seal everything with mastic. Something is going to have to get sacrificed.

  7. #7
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,698
    Just a thought for you to consider. Make a room on the main level for the furnace and then run the supply line through the attic. This keeps the furnace out of that enviroment and easy to service.

    You may even be able to keep the return air duct out of the attic with a little planning.

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Exclamation

    Quote Originally Posted by tomwk View Post
    The challenges I face... My house is a split level and only has a partial basement. ... I considered the mini split but don't like the wall units, plus I have to figure out heating. I don't think the ductless heat pumps can work on the coldest NJ days.

    I think I am going to keep my Lennox G71v furnace and xc21 ac unit (which are top notch products) and move it to the attic. The pro is that I could have much better duct runs without a million turns. ,,, Something is going to have to get sacrificed.
    Envelope the attic with foam insulation to develop a conditioned space.

    How many hours does it go below 20'F in NJ?
    Mini-split heat pump with its various configurations can be used.
    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

  9. #9
    Join Date
    Aug 2009
    Posts
    154
    I looked into spray foaming the attic to make it conditioned space. The town inspectors and architect did not love the idea because 1) the cost around 10k and 2) if you ever re-roof or re-side all the nails will puncture your foam defeating its purpose. Obviously I would foam all attic floor penetrations as best as possible but not going to the extent of foaming the whole attic.

    I will try to designate at least a closet for the equipment on one of the living floors. That way at least the equipment is out of the attic. That is a good idea. Maybe even the return air.

    Of the contractors I asked about the mini splits most said they would only use them in like a 1 room addition. I don't think they were well versed with mini splits.

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    1) Most town inspector are idiots and don't know what they are talking about. Some do, but many are uninformed or misinformed. 2) If a nail penetrates the foam, it won't affect it's performance, anymore than the existing nails do. 3) Get multiple bids. Pricing and quality just like with HVAC can vary greatly. However, I can't argue that it will be a 15+ year payback.

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