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  1. #1
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    Ultra-Aire SD-12

    Teddy Bear or anyone else have experience with these units?

    I'd like to install two of them for a 10K sq ft office space. I like the fact they have OA AND they throw cooler not warmer air.

    I have 10K of humid office space, 74 DB and 70% RH. No OA, poor insulation, design lacking, etc. Too expensive to change the building envelope.

    The existing ductwork I want to tie into isn't insulated. 550 CFM, 4000 BTU, so I'm guessing it'll throw SA at 5 degrees TD? 75 RA and 70 SA?

    Please let me know any pros or cons of these units. Thanks

  2. #2
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    The Ultra-Aire SD 12 will do what you want. How much fresh air do you want? Decide on the amount of outside air verses inside air provide ducts sized for the flow. YOu also can opt out of fresh air when the space is unoccupied.
    I am concerned about you current 74^F, 70%RH. During peak cooling load with +60% cooling cycle, your a/c should be able to maintain <50%RH if setup correctly. I would start by confirming that your a/c's air flow is adjusted to give you a 30^F split verses your return air temperature. A 44^F coil temperature should remove enough moisture to get you down to 50%RH during long cooling cycles.
    The exception is unusually high latent loads caused by high occupancy or excess outside air infiltration.
    What is your supply temp/%RH with 74^F, 70%RH? How many people in the space? What is the climate or temp/%RH outside?
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  3. #3
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    Thread Starter
    Thanks. They're ductless cassettes. All are dehumidifing well but it's on the ocean, lots of rain this year, poor building design, lots of outside air infiltration, etc.

    Yes the OA is a benefit but I'm going to close the damper initially, then revisit the OA intake, damper schedule, etc after the RH is controlled.

    I've never used this model. I like the cold air supply instead of constantly throwing warm air. How cold is the supply air? 3-5 degrees TD? Existing ductwork I'd like to tie into isn't insulated. Thanks again.

  4. #4
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    Thread Starter
    I've used ductless Daikin Quaternity models with good results but it's too small for this office. I'd love to hear any feedback on this model. I know it's not cheap but it could fit well in niche applications. Thanks

  5. #5
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    Teddy Bear or anyone, Ultra-Aire phone number? Thermo-stor in Wisconsin is the factory or a rep? Their tech support number? Any reps in Hawaii? Their home page doesn't seem to any wholesalers listed. Thanks

  6. #6
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    Therma-Stor factory, Madison, WI
    Start with Justin Mundth 800 533 7533. He will answer your questions and get up pointed in the right direction.
    Keep us posted on unanswered issues.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #7
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    Quote Originally Posted by tunaguy View Post
    Thanks. They're ductless cassettes. All are dehumidifing well but it's on the ocean, lots of rain this year, poor building design, lots of outside air infiltration, etc.

    Yes the OA is a benefit but I'm going to close the damper initially, then revisit the OA intake, damper schedule, etc after the RH is controlled.

    I've never used this model. I like the cold air supply instead of constantly throwing warm air. How cold is the supply air? 3-5 degrees TD? Existing ductwork I'd like to tie into isn't insulated. Thanks again.
    The cold dry air from the UA SD 12 is about 10^F cooler than the supply air with 10-15^F reduction in dew point. So mostly latent cooling with less sensible cooling. 8,000 btus of latent cooling per hour per unit.
    Is you current a/c setup with a 30^F split between the return air temperature and coil temperature.How many ton of a/c do you have on the space?
    I agree with your strategy of starting without OA until you get the moisture under control.
    Monitoring the CO2 levels with a number count of the occupants would give us an idea about the amount of outside air infiltrating when the space occupied.
    CO2 meter cost $100
    CO2meter.com
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #8
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    Thread Starter
    CO2 was measured many times with my nice Fluke, it's around 600-700, which is only slightly higher than the outdoor air.

    Split varies, it's ductless cassettes, probably around 13 of them, varing from 1-2 tons, with a total around 25 ton total. They maintain 40-44 degree sat temp. This isn't an AC issue, they all work well. We've replaced 4 of the 13 the last 3 months.

    Split temps or Delta T vary with ductless. Compressors have inverters that'll vary the compressor speed to maintain the sat temp. Trust me, these condensate pumps are throwing out water in all the units. It's just a porous building buildt on a sponge.

    I'll contact them tomorrow morning and let you know how these units work out in a few weeks. Thanks again.

  9. #9
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    Thread Starter
    Tedd

  10. #10
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    Teddy, you can not run 30 TD on AC units normally. I understand low evap sat temp and low air flow will increase dehumidifying but it causes other problems. SEER rating drops, freeze ups, and SA registers will rain inside the space.

    72 RA with 30 TD is 42 SA, which would be 27-32 degree evap sat depending upon the efficiency of the unit, evap approach. AC guys try for 20 TD if possible.

    You say 10-15 TD for the SD-12, is that based upon your experience with these SD-12 units? I'll look again but I thought it was 550 CFM with 4300 BTU. I was hoping for 5 or less TD, but if higher I'll make it work.

    Thanks for all your help. I'll keep you posted in a few weeks. Got approval today, so I'll order them tomorrow. Hoping these newer style units will work well, keep noise down, and be easier to service. I deplore these little bastards pushed against the trusses.

  11. #11
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    Thread Starter
    Ok. 4300 to 5100 BTUs at 350-400 CFM. This should give me a 7-10 degree TD, but that should be fine.

  12. #12
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    Quote Originally Posted by tunaguy View Post
    Teddy, you can not run 30 TD on AC units normally. I understand low evap sat temp and low air flow will increase dehumidifying but it causes other problems. SEER rating drops, freeze ups, and SA registers will rain inside the space.

    72 RA with 30 TD is 42 SA, which would be 27-32 degree evap sat depending upon the efficiency of the unit, evap approach. AC guys try for 20 TD if possible.

    You say 10-15 TD for the SD-12, is that based upon your experience with these SD-12 units? I'll look again but I thought it was 550 CFM with 4300 BTU. I was hoping for 5 or less TD, but if higher I'll make it work.

    Thanks for all your help. I'll keep you posted in a few weeks. Got approval today, so I'll order them tomorrow. Hoping these newer style units will work well, keep noise down, and be easier to service. I deplore these little bastards pushed against the trusses.
    The dew point of the air in the conditioned space is totally dependent on the coil temperature. If you want 75^F, 50%RH, a 55 dew point, your a/c must supply a lower dew point than the conditioned space. A 45^F coil will supply a +53^F 90%RH, a +48 dew point.
    Do the best you can on keeping the coil temperature lower.
    Even a better air filter will lower the air flow and improve the moisture removal of the a/c. The a/c and dehumidifier need about the same temperature to control the dew point of the air in the conditioned space.
    My comments on the SD12 are based woring with the units.
    Thanks for the opportunity.
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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