1. Welcome to Hvacproforums, an interactive community exclusively for HVAC professionals. The collective years of HVAC experience and the knowledge our forum members share make this an invaluable resource for those in the HVAC industry. We have a lot of fun, but make no mistake, we are pros. Hvacproforums is self supporting ...there are NO advertisers here. Do-it-yourselfers and Homeowners are encouraged to seek information elsewhere. Those involved in the HVAC industry are urged to register. its 100% free and easy, Once registered you will have access to the technical forums, Be sure to click over to the new members forum and introduce yourself after registering!

Chilled water fan coil

Discussion in 'Commercial' started by frozensolid, Jun 28, 2012.

  1. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    I was wondering if I can get a little input from you chilled water gurus. I don’t design much chilled water and I want to get it right.

    I have a unit a ground floor unit in a 10 story building that has a 50 year old chilled water fan coil ceiling mounted. It is working like sh!t and the new owners want to change it. The apartment originally had a 3 ton load from what they tell me and that seems about right to me. The old owner closed in a terrace added a couple hundred square feet and the total is now 1800 to 2000 square feet. And the old terrace is 8’ high glass 30 feet long I would say.

    I figure a 4 ton load is closer to being correct and I am told others in the building have increased their units when changed to 4-5 ton coils. The building is supplying 44 degree water with a ¾ chilled water pipe coming in to the apartment. I cannot access the duct work and if it were designed at 3 ton using 300 CFM per ton for chilled water. This would be about 900 cfm.

    I am figuring a ¾ pipe will give me about 8 GPM to the coil I have found a First Co coil that with a six row config will provide 48.0 MBTU at 8 GPM and 1200 CFM. I think I can push the ductwork static a bit higher to accommodate the higher airflow.

    Does this sound about right or am I missing something here.
     
  2. flange

    flange Act like you care and do SOMETHING!!

    Messages:
    12,967
    Location:
    IMT--in my truck
    probably fair, but consider a few things. First and foremost, being a residence, what will new air velocity be? will you create too much air noise? will your new fancoil handle your new static? will your proposed unit handle the building pressure?(often times they do not). oh, and what exactly will all that glass do to your space conditions? you may need to deal with that area by adding a diffuser or two.
     
  3. Catpower

    Catpower The Crowd Pleaser

    Messages:
    22,466
    Location:
    in the Cabana
    Which way does the glass face?

    If it is facing east or west, when the sun is shining in it's going to take about 96000 btu just for the solar gain

    Besides that your numbers look like they would work, might be a little noisier but they will get used to it

    Or they will be hot

    First Company units are good, hell they have to be they are made in Texas, well at least they used to be
     
  4. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    Its noisy as hell already and windows face south and they are the only real load the place has. There is no roof load, one window wall, and one block wall everything else is conditioned space.

    Flange the duct is one straight line and I am looking at .1 one static now. The existing unit is just loud so I think the new unit will actually be quieter than the old.
     
  5. tuna

    tuna New Member

    Messages:
    2,930
    Thats a lot of glass. The cost of a five ton fan coil should not be much more than the cost of the four ton. I think Id go with the five as long as it had a fan that could be slowed down if it was to noisy. Id look at how much capacity the five ton would do vs the four ton with both moving 1000cfm or so before deciding for sure.

    If you have to make any duct transitions 1/2" liner makes a big difference in "unit" noise. Wont help much if its just wistling out the grilles.
     
  6. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    But will I get the tonnage with a 3/4 pipe? Also the first co coil can be ordered with a four speed auto fan package and stat. It slows the fan down the closer you get to set point.

    I am worried that too big may cause humidity problems. Do you think the auto fan will help that?
     
  7. Snoring Beagle

    Snoring Beagle Need Little - Want Less - Love More

    Messages:
    11,148
  8. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    Pretty cool beagle I put it on my Ipad Could come in handy. Bell and Gossett has always had some good tech info.
     
  9. tuna

    tuna New Member

    Messages:
    2,930
    Your 3/4" pipe could be a problem. Looking at a pipe sizer a 3/4" pipe can carry 4 gpm on the high end. With enough pump pressure you could get more flow, but 8 gpm might be tough. You should be able to get the salesperson you are dealing with to figure the capacity of the unit with different flowrates.

    When I suggested the 5 ton unit it was more to get the bigger coil than move more air. Maybe figure you can get 5 gpm of flow. Just let the leaving water temperature be whatever it is, dont worry about normal temperature rise. See what the capacities would be with the 5 ton unit set to move 1200 cfm, and then see the capcacity of the 4 ton with 5 gpm and 1200 cfm. They should be able to plug this information into a computer and get the capacities.

    To me humidity control is all about how cold you make the air. With chilled water you have the ability to slow the air down and get lower temperatures without worrying about compressor issues. Also as AbbyNormal used to stress, turn the fan off when the chilled water is not flowing.
     
  10. Snoring Beagle

    Snoring Beagle Need Little - Want Less - Love More

    Messages:
    11,148
    That auto fan feature is cool. Essential for humidity "semi" control since it doesn't have a humdistat. Comfort levels are a lot higher with the auto fan feature.

    Is the controller wi-fi too? Does it have occupancy and economiser features.

    Also like Tuna brings up by channeling Abby, Does the controller handle the chilled water too?

    Valves? 2 way or three? any hot water? Piping 2 pipe or 4?
     
  11. Catpower

    Catpower The Crowd Pleaser

    Messages:
    22,466
    Location:
    in the Cabana
    The southern exposure on the glass will give minimal solar gain in the summer, it will give quite a bit in the winter though but that would probably be good, but maybe not, might be like a multi story/high rise, might need cooling in the winter
     
  12. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    I Though I could get 8 Gpm out of that 3/4 you think five is my limit?

    No humidistat and the stat does control the water valve, no wifi and only auto changeover.


    We cool 11 months a year down here.
     
  13. Catpower

    Catpower The Crowd Pleaser

    Messages:
    22,466
    Location:
    in the Cabana
    If you are short of water if there's room you can put in a booster pump

    I know it isn't the right way to do it but I've had to do it before and it works, but sometimes the building engineering dept will pitch a bitch, but I doubt an apt has an engineering dept
     
  14. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    I am trying to get with someone at First Co. to see the if a bigger coil will do the trick as Tuna suggested. If not I will likely see If I can retap the branch circuit to inch or inch and a quarter. I won't do a hot tap (ever since I saw a blowout) so either they shut down so I can have a weld-o-let put on or maybe it will be better to walk away.
     
  15. Catpower

    Catpower The Crowd Pleaser

    Messages:
    22,466
    Location:
    in the Cabana
    We have companies around here that specialize it doing hot taps, I've never had one fail from them and then they are liable if SHTF
     
  16. Tap

    Tap i hate it when a velociraptor throws poop at me

    Messages:
    10,253
    Location:
    Lost
  17. Tap

    Tap i hate it when a velociraptor throws poop at me

    Messages:
    10,253
    Location:
    Lost
    You might get away with a 4 ton if your duct work can handle the extra huff n puff. I mean its gonna have a 3 speed motor just slow the fan down........
     
  18. Tap

    Tap i hate it when a velociraptor throws poop at me

    Messages:
    10,253
    Location:
    Lost
    You might get away with a 4 ton if your duct work can handle the extra huff n puff. I mean its gonna have a 3 speed motor just slow the fan down........
     
  19. tuna

    tuna New Member

    Messages:
    2,930
    Looking at a B&G pipe sizer and the "normally used design range" for 3/4" type l copper is 1 1/2 to 4 gpm. I think you could get 5 or so and maybe 8 but that is pushing it.
     
  20. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    12,348
    Location:
    Earth
    I spoke with first co and if I bump up to a 1600 CFM 6 row coil at 5 GPM I can get 47.0 MBTU which I think will do it. I see what you were getting at now Tuna. With the auto fan I likely will be running in med -low at most times except maybe during a hot start. Abby gave me a formula to calculate how much static increase I will get when adding CFMs I will have to find it and see if the ducts can take it.