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  1. #1

    New Store Humidity issues

    Have a new 5ton carrier for approx 800sq ft - the space was just finished 2 months ago and we could feel the humidity so I brought in a thermometer/humidity gauge and checked it. Store is in Morrisville NC. System cycles about 3 times an hour, on for 10min, off for 10, on for ten etc. Originally they had a sliding door open to let in fresh air at about 10% but we completely closed it. Every 10 minutes we go from approx 50% humidity to 70+. Temp is 68 so it feels like crap when humidity is above 70%. HVAC tech came out and tapped the fresh air sliding door closed completely, and adjusted the pulley as small as he could for the direct drive motor which runs constantly, but didn't change a thing. I have asked the engineer to provide the heat load calcs because he said it came up with 6.5 tons but he moved it down to 5.0. I think the unit is WAY to big and doesn't have enough time to dehumidify. I'd rather have it run much longer for efficiency and longevity of the system. I don't cook in the place and only have 4 seats. 1 prep cooler, ice cream cooler and stand up refrigerator and all flourescent lights. HVAC guy is saying he talked to the carrier dealer and everyone is having issues because it's been so humid this summer.

    Has anyone seen humidity swing this much??????? Where is it coming from??? I have a separate unit for about 400sqft for the back of the house where I have big freezers and frig and that doesn't get as humid. On both sides of me are tenants and I have about 12X10 double paned glass facing approx SW.

    Friend said I should just call the insurance and tell them I'm afraid of mold issues and they would force someone, probably the engineer to resize the unit correctly.

    Can someone help me out here with some other ideas.

    Frustrated newbizowner!

  2. #2
    Join Date
    Aug 2004
    Location
    Tucson, Az
    Posts
    337
    Are there a lot of people in and out all the time?

    With the current info it does sound over sized but without the actual load calculations that's just a guess.

    Sounds like the unit is not running long enough for proper De-humidification, as you stated, but again, just shooting from the hip.
    Jim
    Tucson, Az
    Keeping the Ice Cream Frozen!

  3. #3
    Join Date
    Jan 2005
    Location
    Emerald Coast
    Posts
    965
    .

    You want to make sure the condensate drain is properly trapped. The unit should be making
    buckets of water under those conditions.
    ..
    Do not attempt vast projects with
    half vast experience and ideas.
    ...

  4. #4
    Join Date
    May 2009
    Location
    Cummins, GA
    Posts
    1,561
    5 tons for 800 sq ft?

    What kinda store is this? A tanning bed? Geez.

  5. #5
    Quote Originally Posted by market-tech View Post
    Are there a lot of people in and out all the time?

    With the current info it does sound over sized but without the actual load calculations that's just a guess.

    Sounds like the unit is not running long enough for proper De-humidification, as you stated, but again, just shooting from the hip.
    Received the load calcs and the engineer entered 34 people for the load without even asking me one question about my business. The NET GAIN of 19,298 or approx 1.5 tons just for people. Even the amount per person seems high from what I've found on the web. (19298/34) = 567. In a very busy hour we may have 25 people but they're in the store for 5-10 minutes, and there will be a small load from the door opening and closing. 3 working + 25/6 (6 people on average for 1 hour) = 7.16 people per hour instead of 34 or 80% too high.

    2nd problem IMHO, was the total came to 6.15 tons cooling, and he installed 7tons - A 2ton and a 5ton. If I knew that, I would have told him to put in 6 tons.

    If the # of people are corrected, the 5 ton should have probably been a 3ton, hence my humidity problem.

    What I have done to rectify the problem temporarily is turn the fan from Always ON while we're here to AUTO. This will cause more wear and tear for the fan motor but keeps the building between 43-55% humidity. MUCH BETTER but against code because the air should be moving for commercial space.

    I may need to either hire another HVAC guy to do another load calc or talk to the engineer and have him redo the numbers. Either way, I don't think I should pay for replacing the unit since the load calcs are off, but I don't think the engineer is going to come out of his pocket and replace my 5ton with a 3ton unless he is pushed to do so.

    I did talk to the Carrier rep and he said there are dehumidifiers I can use, or turn on the heat strips, which I can't because it a Heat pump and I think this is a band-aid anyway, or even use a type of CO detector which will possibly allow me to run they way I am with the fan on auto, but within the code.

    Bottom line is the unit is too big, and to fix it someone needs to pay for a new unit. I think the engineer dropped the ball on this on and should replace my unit. I know it may not sit well with people on this board because you are in the business, but I had to PAY someone to design the system but it wasn't done right. I shouldn't have to be stuck with it..

    If anyone has any other ideas or thinks I am incorrect in how I've calculated this, PLEASE let me know.

    I'll follow up and let everyone know what the outcome is.

    Thanks
    Newbizowner

  6. #6
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

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    Last edited by beenthere; 07-21-2013 at 04:22 PM. Reason: Non Pro * member

  7. #7
    Join Date
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    PA
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    highhead666, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,637
    Quote Originally Posted by newbizowner View Post
    Received the load

    Bottom line is the unit is too big, and to fix it someone needs to pay for a new unit. I think the engineer dropped the ball on this on and should replace my unit. I know it may not sit well with people on this board because you are in the business, but I had to PAY someone to design the system but it wasn't done right. I shouldn't have to be stuck with it..

    If anyone has any other ideas or thinks I am incorrect in how I've calculated this, PLEASE let me know.

    I'll follow up and let everyone know what the outcome is.

    Thanks
    Newbizowner
    Go with a small whole house dehumidifier for several reasons. This provide <50%RH during peak cooling loads.
    In your climate, even a small a/c is unable to maintain <50%RH, during no/low cooling loads and outdoor dew points are +60^F.
    You will be able to leave the fan "on" and maintain <50%RH during low/no cooling load conditions.
    Check out the Ultra-Aire 70H. Much cheaper than replacing the a/c and will maintain <50%RH during low/no cooling loads.
    Keep us posted.
    Regards TB
    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"

  9. #9
    Quote Originally Posted by teddy bear View Post
    Go with a small whole house dehumidifier for several reasons. This provide <50%RH during peak cooling loads.
    In your climate, even a small a/c is unable to maintain <50%RH, during no/low cooling loads and outdoor dew points are +60^F.
    You will be able to leave the fan "on" and maintain <50%RH during low/no cooling load conditions.
    Check out the Ultra-Aire 70H. Much cheaper than replacing the a/c and will maintain <50%RH during low/no cooling loads.
    Keep us posted.
    Regards TB
    Teddy, I agree a whole house dehumidifier would help in this situation, but it is still more of a band-aid instead of a fix. The current unit cycles a lot even on the really hot days, and it doesn't keep the RH anywhere near 50% for more than a few minutes. Additional considerations are the wear and tear on the unit cycling, plus the added cost of electricity to run the dehumidifier.

    GC discussed with the Engineer who stated he designed the system for a per sqft load of X people, and had nothing to do with the load of my store. He further stated that the Landlord may not allow me to reduce the HVAC too low because of issues with new tenants if I leave the space prematurely.

    With using the new load calcs by reducing the people load down to properly take into account my business, the engineer has agreed we could reduce the capacity by 2tons. Option 1 - reduct the back of the store so it uses the 5 ton for the whole store, and leave the 2 ton idle which was used for the back of the store, or 2 - replace the 5 ton with a 3 ton. I've discussed with the Landlord and they have a minimum of 300-325 per ton, so I'm even above that limit with the reduced size, so he approved my replacing the unit.

    I'm opting for #2 because it still gives me redundancy of 2 units, plus will improve RH because smaller unit in all cases will run longer. Now for low load days where RH is high anyway, that would be fixed with your solution, but those days should be in the minority anyway.

    I have discussed this issue with Chris, an engineer from advancedenergy.com, and I can further reduce the RH by not running the FAN continuously as it picks up moisture from the coil which was just extracted and just dumps it back into the space quickly. Setting the fan to Auto, instead of ON will only improve the RH inside the store further.

    I've left a message with the GC so hopefully it will not take long to replace the unit.

    Newbizowner

  10. #10
    From previous message, site is advancedenergy.org not .com

    Newbizowner

  11. #11
    Quote Originally Posted by newbizowner View Post
    From previous message, site is advancedenergy.org not .com

    Newbizowner
    OK. 1 Year later and I'm in the same spot I was last summer. GC stood behind the engineer, and the engineer said to change anything I'd would have to pay for new unit, or redo ducts and not use the 2nd unit! Yea thats right pay after being in my business 4 months on a system he designed.

    I talked to the Main Mechanical City Inspector who approved the permits, who couldn't do anything since the system was "designed" by an professional engineer. He suggested I call someone, and after a brief conversation, the Technician didn't do load calcs for commercial.

    I filed a complaint to the NC Board of Examiners for Engineers and Surveyors in August. Met with a rep told them everything I went through. In May I received a response, which stated they did conduct and investigation and reviewed my info and the respondent's explanation, and the results of the investigation. This is the results and I'm quoting from the letter "After a thorough review of all matters relating to the case, the Review Committee recommended and the Board closed the case. The Board's decision was based upon lack of evidence of gross negligence, incompetence or misconduct for the charge of having affixed seal to an inadequate document, failing to protect the public. The charge was deemed unfounded. The charge of having failed to properly certify documents did not rise to level requiring disciplinary action."

    After I called and complained, the rep said the only way to re-open the case was to have another Engineer do a load calc and show where his was wrong. I said no came to my store and very what I complained about. I also asked to see the response from the engineer, both of which were denied?!

    So I contacted the North Carolina State Board of Examiners of Plumbing, Heating and Fire Sprinkler Contractors, and they forwarded me to the NC Board of Examiners for Engineers and Surveyors who just closed the case.

    Decided to try and get another load calc done, so I contacted several Engineers who were referred to me by the HVAC companies they did work for and NO-ONE has called me back.

    This is ridiculous, I follow all the City, County permitting rules and regulations to build out my business and no one will help me with this poster child for an Oversized HVAC installation. During the 95 hot and humid days, I'm sitting at 68-70 degrees with 58-61% humidity.

    I don't want to have to spend good money after bad by just hiring an attorney to sue. Shouldn't there be some agency that will help me correct this, since I've followed all the rules.

    Anyone have any ideas?? I'd really appreciate it.

    Thanks
    Newbizowner

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,637
    The idea that you can have humidity control with a conventional a/c will only work when the sensible cooling load is enough to remove the latent moisture load. During peak cooling loads, yes. During low/no sensible cooling loads, not so much. If you really want 50%RH during low/no cooling loads, get a good whole space dehumidifier.
    People just learn to live with high humidity if they are not using a dehumidifier. The other option is reheat which is expensive to operate when compared to a high efficiency dehumidifier like the Ultra-Aire which remove upto 8 pints per KWH. The dehu also provides humidity control even with the a/c is off.
    Keep us posted.The a/c trade is not aware of the a/cs inability to remove moisture during low/no cooling loads?????
    Regards TB
    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"

  13. #13
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,498
    The no load is being created artificially by quickly reaching setpoint by using too large a unit.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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