Unique system and now an addition: Opinions wanted
Page 1 of 3 123 LastLast
Results 1 to 13 of 32
  1. #1
    Join Date
    Feb 2008
    Location
    Charlottesville, VA
    Posts
    15

    Unique system and now an addition: Opinions wanted

    Hi,

    This is somewhat of a complex (and long question). Sorry.

    I am a Homeowner. We live in central Virginia. We have a 2000sqft home that is well insulated. We have hydronic RFH. For cooling we have a slightly unusual system. We have a 2 ton chiller (Aquaproducts)which feeds cooled fluid to a 2 ton Spacepak high velocity system and small diameter/high velocity ductwork. The chiller also cools water that is circulated in the radiant system for some degree of radiant cooling. The system is just barely adequate. I think that the fault is that the chiller is too small, as the fluid temperature into the Spacepak system can be as high as 55F. Because of this the chiller runs continuously during the summer. The house is just barely OK except for runs of several days over 95F when it can get pretty warm inside.

    Anyway, we want to build an addition. It will be 3 stories, with each floor being about 320 sqft (a little over 1000sq which includes a finished basement room). We have now gotten 2 proposals for cooling the addition and helping the rest of the house. I am also wondering about other options.

    Proposal #1: Increase the size of the chiller (5 tons)Unico and add an additional 1.5 ton Unico fan coil/distributor. Cool the addition with high velocity ductwork. The estimate for this is expensive.

    Proposal #2. Increase the size of the chiller to 4 tons (Multiaqua). Use some of the chilled fluid to a) feed the current Spacepak, b) feed chilled water to 2 Multiaqua air handlers in the addition situated in such a way as to primarily cool and condition the Addition as well as help the rest of the house and c) supply cooled water for the radiant system. I have gotten a quote for this and it is expensive.

    Other ideas (mine):

    1) 2-3 zone Mini-split system to cool and condition the Addition (and some of the house). This would hopefully take some of the load off of the current system.

    2) Install a small conventional heatpump/AC with conventional ductwork in the addition which would hopefully also take some of the load off the house. Right now the plans do not take into consideration conventionally sized ductwork, but I imagine we can change that.

    I do not know if anyone has done a Manual J calculation (but will be asking)

    Thanks for letting me ramble.

    Bart
    Last edited by bartmanbartman9; 02-29-2008 at 10:16 AM. Reason: removed $$$ references

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,279
    First of all, you need to remove the pricing references in your post before a moderator does that for you (and gives you a warning).

    Secondly, regarding your present chiller system's problems...are you saying that the water temperature that is ENTERING the Spacepak air handler is 55 degrees? If so, that's too warm. At minimum, the entering chilled water temperature to a cooling coil needs to be between 42 - 45 degrees for comfort cooling.

    However, you also state that chilled water is pumped through your radiant system, which at this point I'm assuming is in the floor of your home? So...perhaps the 55 degree supply water was chosen in order to keep your floor from turning into a giant water condenser. That is always the tricky part about running cold water through a floor radiant system...how to keep the floor surface above the dew point of the room.

    Without actually being at your home, just a cursory opinion of mine would be your system is not adequately dehumidifying the house (warmer cooling coil in the Spacepak air handler), and the chilled floor itself can only give you a measure of radiant cooling...in other words it feels cool to the touch, but the air in the room is sticky and warm.

    Sans discussion about your planned addition, I think your present system would be better served by removing the radiant side from the chilled water loop, lowering the supply chilled water to 45 degrees, and sending all that water to your Spacepak air handler.

    Of course, anything beyond this, when considering your present home and the planned addition, should involve a bit more intelligent system design than you've currently experienced. A Manual J heat load calculation, yes. Many more factors play into this, depending on what type of system is being considered for installation.

  3. #3
    Join Date
    Feb 2008
    Location
    Charlottesville, VA
    Posts
    15
    Actually the water to the radiant floor system is tempered by a mixing valve, so we can adjsut that temperature independently. The chiller does much of the time, inject 45F water into the SpacePak, just not consistently. My (unsupported theory) is that likely the the combined load of the Spacepak air coils and the chilled floor is diminishing the ability of the chiller to supply properly cooled water.

    Thanks for your input and the heads up!
    B

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Your addition will likelt abut some portion of the existing home,so if you have a separate system for the addition,the load for the existing drops,based on the amount of formerly exterior wals/windows that are now interior.

    I agree the water temp is to low.

    You need load calculation(Manual J) to determine the new load or loads if two systems.

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,058
    Quote Originally Posted by bartmanbartman9 View Post
    Actually the water to the radiant floor system is tempered by a mixing valve, so we can adjsut that temperature independently. The chiller does much of the time, inject 45F water into the SpacePak, just not consistently. My (unsupported theory) is that likely the the combined load of the Spacepak air coils and the chilled floor is diminishing the ability of the chiller to supply properly cooled water.

    Thanks for your input and the heads up!
    B
    I would agree with your theory and Shophound also gave you some good pointers.

    Where are you in Va.?

  6. #6
    Join Date
    Feb 2008
    Location
    Charlottesville, VA
    Posts
    15
    Charlottesville

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,697
    As the others have said. The addition will take some load of the existing structure.

    I would go with mini splits for the addition, and see how much better the existing structure does after that.

    You can always increase the size of the chilller later if need be.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,279
    Quote Originally Posted by bartmanbartman9 View Post
    Actually the water to the radiant floor system is tempered by a mixing valve, so we can adjsut that temperature independently. The chiller does much of the time, inject 45F water into the SpacePak, just not consistently. My (unsupported theory) is that likely the the combined load of the Spacepak air coils and the chilled floor is diminishing the ability of the chiller to supply properly cooled water.

    Thanks for your input and the heads up!
    B
    I think your theory has some support from both myself and my peers. Therefore, if you want to retain the radiant cooling feature, increase the size of your chiller so it can handle both the Spacepak load and the radiant floor load. Just a guess...perhaps the original system designer thought that between the well insulated house, the high velocity air movement of the Spacepak system, and the radiant floor cooling, a two ton chiller would be adequate. What I can't see from here is how well the area below your radiant piping array is insulated, being that I don't know if we're talking slab on grade or a home with a basement or crawl space. Either way, if the area beneath the radiant array is poorly insulated, you're basically heating and cooling what's below that in addition to whatever heat transfer occurs through the floor. If your house is slab on grade, and there was no insulation installed below your radiant piping, let it be known that soil is a lousy insulator. Ask anyone that has an earth sheltered house that skipped insulating the shell between earth and home.

    Initially, for your new addition, I think I'd also take a wait and see method...the exterior wall of your present home will become an interior wall once the addition is completed. You might also look at a multi-split system for the addition, such as made by Daikin, vs. increasing chiller size and running chilled water piping out to the addition, or going with one mini-split per level, which puts three condensers on the ground outside your new addition. A multi-split will have just one condenser, in addiiton to your chiller.

  9. #9
    Join Date
    Feb 2008
    Location
    Charlottesville, VA
    Posts
    15
    Quote Originally Posted by shophound View Post
    Just a guess...perhaps the original system designer thought that between the well insulated house, the high velocity air movement of the Spacepak system, and the radiant floor cooling, a two ton chiller would be adequate. What I can't see from here is how well the area below your radiant piping array is insulated, being that I don't know if we're talking slab on grade or a home with a basement or crawl space. Either way, if the area beneath the radiant array is poorly insulated, you're basically heating and cooling what's below that in addition to whatever heat transfer occurs through the floor. If your house is slab on grade, and there was no insulation installed below your radiant piping, let it be known that soil is a lousy insulator. Ask anyone that has an earth sheltered house that skipped insulating the shell between earth and home.
    Thanks again for the input. I think you are correct, that the initial installer thought that the combination of the radiant floor cooling and the Spacepak would handle it all. OTOH, I would think that cooling is cooling to some extent and that you would need a certain amount of power to extract the heat, no matter the method. I have spoken about this to him in the past, and he feels that the chiller was innappropriately labeled/marketed as a 2 ton unit, when in fact it is not that powerful. Oh well.

    The same installer is the one who wants to increase the size of the chiller by using the Multiaqua unit and cool the addition with the water-fed Multiaqua split system blowers.

    Our house is built with a basement. Beneath and around the basement slab are 1.5-2" (I can't remamber exactly) of polystyrene foam. The house is well insulated with low e windows.

    Thanks again for the rec's.

    B

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,697
    What temp do you set your thermostat at for cooling.
    Some times HV systems are designed to maintain a higher temp.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #11
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,279
    Quote Originally Posted by bartmanbartman9 View Post
    Thanks again for the input. I think you are correct, that the initial installer thought that the combination of the radiant floor cooling and the Spacepak would handle it all. OTOH, I would think that cooling is cooling to some extent and that you would need a certain amount of power to extract the heat, no matter the method.
    Not exactly, when speaking of what you just said. Cooling would be cooling if there was only one type of cooling to occur. With indoor comfort cooling, heat removal must occur in two forms; sensible (heat you can feel) and latent (heat that causes water vapor to become liquid water when this heat is removed from the water vapor). If the original installer did not perform a heat load calculation on your home, he had no idea what the sensible to latent ratio was for your particular home on a design day.

    I
    have spoken about this to him in the past, and he feels that the chiller was innappropriately labeled/marketed as a 2 ton unit, when in fact it is not that powerful. Oh well.
    That sounds like a weak excuse to me. If he's dealt with this type of equipment before, he should be more familiar with his product line than that.

    The same installer is the one who wants to increase the size of the chiller by using the Multiaqua unit and cool the addition with the water-fed Multiaqua split system blowers.
    If you seriously consider using this installer again, hold him to a higher degree of system design. You want load calculations for your existing home plus the addition. You want the existing problem remedied and no shortfall of capacity for the new addition. I can see why you might want to just upsize the chiller and expand on what it cools, since you already have the chiller and the infrastructure for it in your existing house. That being said, I would not accept him just throwing any higher size chiller in there willy nilly. He needs to crunch some good, hard numbers and get it right. You have too much at stake riding on it.

    Our house is built with a basement. Beneath and around the basement slab are 1.5-2" (I can't remamber exactly) of polystyrene foam. The house is well insulated with low e windows.
    Is the area below the first floor radiant system insulated...IOW if you were to go down into the basement and look up at your radiant system for the first floor, would there be insulation or would there be unblocked access to the radiant piping?

    Thanks again for the rec's.
    You're welcome.

  12. #12
    Join Date
    Feb 2008
    Location
    Charlottesville, VA
    Posts
    15
    the areas between the joists on both the 1st and 2nd floors are insulated, as is the basement slab (as I mentioned). All floors, including the basement slab have PEX tubing for radiant.

  13. #13
    Join Date
    Feb 2008
    Location
    Charlottesville, VA
    Posts
    15
    Quote Originally Posted by beenthere View Post
    What temp do you set your thermostat at for cooling.
    Some times HV systems are designed to maintain a higher temp.
    Typically set it for about 75F. Best it usaully does is 77F (even if we set it lower).

    B

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event