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Recent content by tys90

  1. tys90

    Wood Waffle Ceiling & Ceiling Pocket Coverage

    We have been tasked with adding sprinkler coverage to a building with a historic wood waffle ceiling. We are not allowed to modify the ceiling per the State Historical Preservation Office. I believe this ceiling qualifies as having ceiling pockets per NFPA 13 8.6.7.1. They meet all the...
  2. tys90

    Emergency Generator Ventilation

    Even if it isn't in writing somewhere, it sounds like a good idea. You wouldn't want your discharge damper closed while the generator is running.
  3. tys90

    How do I quietly reduce humidity in a room?

    There are small dehumidifiers that can be ducted. Do you have a room near by with a floor drain? Basement or utility room? You could install one there and duct it to your bathroom. Probably won't be cheap and is overkill for a space that small but that should significantly reduce the sound...
  4. tys90

    Frost Protection on AHU Unit with Plate Heat Exchanger Heat Recovery

    I'm not sure I understand the question. The discharge air temperature has nothing to do with preventing damage to the coil itself during cold conditions. 35% glycol has freeze protection down to roughly -16C so you should have no issues with freezing damage to the coil. Is this a preheat...
  5. tys90

    VAV box minimum postion and ventilation equirments

    Bastiat's correction is critical to this post and it hinted at the key to determining minimum VAV box positions, which is what I believe was the OP's original question. The very basic answer is: you can set your VAV box minimum to whatever you want as long as you satisfy the requirements of...
  6. tys90

    Pressure Loss Through Symmetrical Wye

    Total pressure drop through a fitting (referred to as Dynamic Loss in ASHRAE) is your coefficient times velocity pressure. Just because the number is negative doesn't change the equation. See example 7 in your the Duct Design chapter.
  7. tys90

    Class B Operating Room

    dbill74 - can you point out the section that refers to OR air not allowed to be recirculated?
  8. tys90

    ME career limitations if leaving hospital and plant work for school and church projects

    As an ME in HVAC design, I've always viewed variety as a good thing as long as you still maintain a speciality, such as hospital design. Having a wide range of experience helps in many ways but being known as the "go to" guy for a certain market sector is extremely valuable in my opinion. This...
  9. tys90

    Chiller Optimization

    Is it possible your secondary pumps are reacting too fast to the change in pressure? This could cause it to overshoot the necessary flow required to satisfy coil demand and cause a chiller to come online too soon. Same thing would happen in the reverse. Another option would be to look at 2...
  10. tys90

    Minimum air off-coil temperature

    That's not correct. An infinitely large coil is capable of supplying air infinitely closer to the chilled water supply temperature.
  11. tys90

    Minimum air off-coil temperature

    There are a number of reasons to supply higher temp air in data centers. It's usually for efficiency and so you don't condense on the coil. Why don't you ask the vendor?
  12. tys90

    3D Printing Heat Exchangers (Air/liquid)

    There seems to be some research into smoothing 3D printed parts using acetone vapor baths but I'm not sure how that would affect the integrity of a complex part like a heat exchanger. I'd be curious to know what the temperature limits are of these 3D printed materials. A quick google makes it...
  13. tys90

    Stair Pressurisation Fans - High Rise

    Do you have a copy of the Handbook of Smoke Control Engineering? There is a chapter that extensively covers stairwell pressurization. For that building height, it recommends a thorough analysis using CONTAM. You may end up wanting multiple injection points, if they don't want a mid-level...
  14. tys90

    Design-Build competitions sustainable?

    We've worked on the design side of federal Design-Build construction projects after being selected by the contractor, who already has the contract. We are continually baffled by how the scope and budget is decided. urgross hit it on the head as to why this happens and why the design-build...
  15. tys90

    High Efficiency Furnace Roof Termination 10 feet from the property line.

    Assuming these are gas-fired, I believe you will need to follow the International Fuel Gas Code. IFGC 2009 503.8.4 indicates that you can't terminate condensing vents over walkways where water and vapor may cause nuisance or hazard (probably ice or water pooling). Otherwise I don't see any...
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