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Dental Office heat gain

I don't know if the sterilizer is in a separate room but I think it is in the common area. The ops have no doors and are all wide open. There are usually 7 staff and about 10 to 12 others inside the structure. There are no windows that face south and the Northern part of the structure is in woods. There are some Westerly facing windows however. I really want to see what kinds of updates she had done in the last year. I told her to put a big supply register right under the sterilizer to try to disapate the heat but doesn't sound like that is what they did. Humidity may be a factor but nobody in the area uses a dehum function on their split systems because we generally see dry summers.

Thanks to all and happy Wednesday.


  • Darin(in Michigan)_3
    Darin(in Michigan)_3 Member Posts: 28
    Dental Office heat gains

    How would a person go about finding the heat gain(in BTU/H) of individual components in dental office. My sister has had all kinds of work done at her office to correct an overheating condition. In the morning, the office is fine and at late afternoon, it's above 80. She has a 2200 sq ft facility with seven ops and a large sterilizer. Computer terminals are in each op with two at the front desk and one in her office. I would welcome any questions but am curious about a one stop resource to get a feel for the total btu gain of the lights, comps, etc versus HVAC tonage.

    Again, I know there are too many variables not listed and I will address them later.

  • Gregg Jackson_7
    Gregg Jackson_7 Member Posts: 2
    heat gain

    its hard to say how much cooling she would need without seeing the space but i can tell you that it is possible to convert the individual electrical items to btu/h. Take the wattages of all the components and multipy by 3.5 (3.4129) to come up with the btu load. Computers (with monitor) usually are in the 200-250 watts range. The sterilizer may hae a significant increase on your load (not sure). You can also account for 400 btuh per employee. The individual numbers seem miniscule but can add up to an additional ton or ton and a half. My guess (based on square footage) is that you are in the 5 ton range with and additional 1 to 1.5 tons for interior conditions. It could be more or less though obviously. I would hire someone to do a proper heat gain calc and examine your ductwork to be sure it is sized properly with adequate return air also.
  • Darin(in Michigan)_3
    Darin(in Michigan)_3 Member Posts: 28

    Thanks Greg. She does all my dental work for zippo(can't beat that) so any help I can give her she deserves. I figure she has a five ton unit and she has had different techs tell her the unit is running as good as it can but late in the afternoon, the office is up above the 80 mark. It could have something to di with the zone kit. I just want to get my ducks in a row before I make any hasty decisions
  • don_185
    don_185 Member Posts: 312

    A commercial load calc would tell the story.

  • tim smith
    tim smith Member Posts: 2,752
    Re: load on dental lab

    I would bet that you are probably around 300sft per ton maybe higher in your location with it being a dental office. Do the windows of the procedure rooms face south or west or are they interior rooms? The lights in those rooms seem to be the biggest offenders along with the electronics. Maybe try downloading demo from Wrightsoft which may give you enough trial info to do the calculation pretty close. They never let you print or change locality so that may screw it up. Good luck, Tim
  • Brad White_185
    Brad White_185 Member Posts: 265
    All Good Advice

    All of the responses have the right nuggets. To add my $0.02 at risk of repeating or re-stating:

    I have designed a good number of medical facilities (but fewer dental facilities but still some valid experience). The last one, a few years ago, had about a dozen operatories and a full floor fit-out of a very large practice as an example. I have found much of the "load foraging" and zoning are the most crucial parts.

    In other words, if the sterilization core and back-of-house prep rooms are joined with exterior patient operatories then someone will be unhappy. One would hope that the former would be grouped on a dedicated zone. It is these loads which contribute a very strong "base" load and that does not need to be coupled to fluctuating exterior zones.

    The operatories have fairly steady internal gains, the largest variable being the exam light (with a high radiant component). That is mostly directed at the patient but the convective components do go to the space in general. I typically take those lamps at 75% diversity. They are on for about 20-25% of a given workday but the lingering off-heat goes on for a while. Regular lighting I take at 100% diversity.

    Nowadays they usually have that DVD video reel going, showing before and after shots of cosmetic dentistry. Some have plasma screens, a high radiant output to be sure. Specifically, make your own inventory of what is in the room, what is "on" and for how long. I usually count three people per operatory, sometimes four if dental surgery.

    If the dental hygienist is 19 and perky, add another 250 BTUH. :)

    The other part about operatories is latent load. Folks are gowned up today per current health protocols so keeping Dr. DeSoto from sweating up under his goggles is a mitzvah. Size sparingly for maximum dehumidification or better yet incorporate a dehumidification mode which over-rides temperature.

    Other than calculated internal gains, your exterior gains are taken as per a normal building. Note well though that most operatories use blinds for privacy so the sensible solar heat gain factors increase somewhat due to the hot buffer space created. A good program will sort this out.

    Document everything, double check, then rinse and spit. See the receptionist for a follow-up and floss daily.

  • Brad White_189
    Brad White_189 Member Posts: 16
    Sterilizer Capture

    Personally, I think the better approach to limiting the gain from the sterilizer is to put a hood over it and exhaust the heat before it impacts the space.

    Supplying below it will still impose 100% of the heat and humidity into the space and back to the system.

    A simple canopy hood with a low-speed or small fan will take away most of the jacket sensible loads and not deplete the space.

    A higher speed fan with a twist timer (or a two-speed fan to high speed) would be used when the door is open and latent loads take a jump. That mode would only run 10 minutes or so and also will limit the ventilation demand on the AC side.
  • mtfallsmikey
    mtfallsmikey Member Posts: 765
    I wrote about this one a while back

    There are 420 Dell routers located on one floor of one of my buildings in the general office space, not in a data center. And the tenant wonders why the space temp approaches 100 deg. when the system is in the unoccupied mode! After some wrangling and finegaling, I got some solid numbers from Dell on the BTU output of these devices. Enough heat generated to take care of 10 average size houses!
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