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  1. #1

    Do I really need hot gas reheat?

    I'm involved in the renovation of a retail building into a medical office building in Northern Indiana and the mechanical engineer is telling me I need to have hot gas bypass reheat feature on the RTU's for humidity control.

    I manage and maintain a lot of office and retail spaces and I can't recall one with this type of unit or having a problem with humidity control in any of them.

    Is this something that is really needed and are there alternatives to this option on the RTU's?

    Also, it's being suggested that I install an additional RTU for heat only to warm the 10 foot high return air plenum in the winter to keep cool air from falling back into the spaces through the return air grates. Again, I don't have this issue in any of my other spaces. Is it necessary?

  2. #2
    Join Date
    Jan 2009
    Location
    Indiana
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    3,228
    medical requires different things than just retail space. What made him come to this conclusion. Code? storage of medical devices, material, or meds that has humidity concerns?

  3. #3
    Join Date
    Apr 2006
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    mechanical room
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    1,242
    look at the Aaon rtu's, they make unit's for these type of applications, you could use elect. reheat, hot gas reheat etc., we take care of a outpatient surgical center, 2 key things for them is fresh air, and humidity, it's all in the controls though gotta have precise controls in my opinion, ask the medical facility what are there requirements and just build the system accordingly

  4. #4
    Join Date
    Feb 2010
    Location
    Cal
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    1,578
    If you have reason to believe that the engineer is not the right person for the project, hire a your own professional engineer to protect your interests.

    Comparing retail mech'l to heath care mech'l (if done right) is like comparing the people who work in each.

  5. #5
    Join Date
    Apr 2002
    Posts
    11,808
    If they perform procedures in there, quite often they may want it 68F or even chillier with humidity under control.

    There are also a lot of air change requirements, areas of positive pressure, negative pressure, good chance of more outside air than typical.

    Its not like an internet person is there or has the plans in front of them.

    I did a medical centre once, like a neighbourhood walk in clinic and I ended up with some stand alone dehumidifiers.

    I did four surgical suites and had massive reheat.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #6

    Confused Thanks for all the input!

    This is a walk-in neighborhood medical clinic. The clinic doesn't have any specific humidity control requirements, this is just coming from the mech engineer.
    If i can accomplish the same thing with electric reheat i think it would be more cost effective short term.

    Thoughts?

  7. #7
    Join Date
    Mar 2010
    Location
    Morgan Hill Ca.
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    1,171
    Quote Originally Posted by JCM1120 View Post
    This is a walk-in neighborhood medical clinic. The clinic doesn't have any specific humidity control requirements, this is just coming from the mech engineer.
    If i can accomplish the same thing with electric reheat i think it would be more cost effective short term.

    Thoughts?

    Depends on the electrical requirement for the reheat..

    A hog gas heat reclaim coil requires nothing additional as far as power....Is this an OSHPD improvement, may check that out....You may be old and gray by the time everybody is "happy"...

    It really depends on the amount of outside air required...

    GT
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

  8. #8
    Join Date
    Mar 2003
    Posts
    7,314
    your system is sized for a full load occupancy. during summer months with a load that it less than full load, you either need a way to control humidity with capacity or airflow reduction, reheat, or both. hot gas reheat is kinda free but not really. it is cheaper than electric terminal reheat though i am sure. when you pul those btu's out of the space, and are not near full load, you have a tendency to overcool the space and not properly dehmidify. in patient care areas this can be important. We deal with a lot of surgery centers who use this type of scenario, as well as hgb. it costs more obviously, but can save you on remediation costs for mold, comfort, and that spinning electric meter if those are used. as far as the above ceiling, i like the idea. many centers around here are architecturally nice, but have high, peaked roofs. the above ceiling is cold, with just batts of insulation to isolate the occupied space. As soon as a lazy tech goes in the ceiling to look for something like a wate rleak or whatever, the insulation ends up in a ball and is rendered useless.

  9. #9
    Join Date
    Feb 2005
    Location
    In a van by the river
    Posts
    618
    You can get a Lennox with Humiditrol. Controls, hot gas bypass and reheat coil already installed. Don't know if they're upgrading units but definately worth it. If high humidity exists, it'll take care of it.
    ## + years in the field never made you a know-it-all This industry is far more diverse than you are

  10. #10
    Join Date
    Apr 2002
    Posts
    11,808
    york has the DR and ZR series packages
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #11
    Join Date
    Sep 2008
    Location
    Cedar Rapids, IA
    Posts
    476
    Quote Originally Posted by JCM1120 View Post
    This is a walk-in neighborhood medical clinic. The clinic doesn't have any specific humidity control requirements, this is just coming from the mech engineer.
    If i can accomplish the same thing with electric reheat i think it would be more cost effective short term.

    Thoughts?
    If the clinic is associated with a hospital it will be held to very strict standards. Most hospitals are JCAHO certified and in order to get that certification their clinics must meet the same standards as the hospital itself. Also HCFA (the federal agency that controls medicare funds) has a lot of specs that are only listed in the federal register. Your local bldg code enforcement people will not have a clue. If your architect / engineer are experienced with medical facilities let them do what they are paid for. If they do not have the experience get someone who does. It will be less expensive in the long run.

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