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  • Users: cry22
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  1. cry22

    Elevation Head in a Closed-loop Chilled Water System

    Pay attention to very high elevations though. If the water column is say over 350 feet high (30-story plus building), then watch for your valves and fittings pressure rating at the bottom of the riser, as they may see a pressure larger than their rating. valves rated at 125 PSI at the lower...
  2. cry22

    Hvac system in hot and humid climate

    dbill74 in a hot and humid climate, the single DX system for high occupancy is always way oversized, meaning that during low occupancy, the DX will overcool the space too quickly and then has to sit there 10 to 20 minutes without cooling (i.e without dehumidification). This kind of situation...
  3. cry22

    VAV box reheat airflow setting

    Take your primary airflow from 55 to 95 (well, 85 can be OK for not so cold climates), i.e. min VAV box setting PLUS perimeter heating load (wall, glass, infiltration loads served by the box)
  4. cry22

    Ac drain pipe size

    Just google and you get the answer http://publicecodes.cyberregs.com/icod/imc/2009/icod_imc_2009_3_par078.htm
  5. cry22

    Cooling Tower Blowdown Best Practice

    Well Bull Looks like you do not need any advice, do you? you say "IT IS the best solution". Wonder why post anything as you appear as god and his prophet in your conclusion. Your wording is weird, incomprehensible, connect blow-down to condenser water return? blow-down is to the sanitary Bull...
  6. cry22

    Cooling an Electrical Room via Ventilation

    We always air-condition switch gear rooms, whether housing transformers or not. You need to use two AC units ideally floor mounted with ductwork so you don't have to deal with condensate over electrical equipment. two 4-ton units will do you just fine. Install an exhaust fan to operate in winter...
  7. cry22

    what is maximum supply air in room without return?

    The allowable clearance for a one-hour fire rated door is 3/4" (Google it - or see NFPA-80) Typical applications are for rooms adjacent to hallways, some rooms require smoke detectors and smoke dampers (storage rooms over 100 SF), by pressurizing the room, with air ex-filtrating through the door...
  8. cry22

    Hvac system in hot and humid climate

    DOAS with enthalpy wheel and VRF is my choice. Evaluate if you need reheat at the DOAS unit depending on your load. You may be able to use DOAS air directly into the space without reheat and downsize your VRF units. DCV should be used too per new ASHRAE 90.1, Single zone VAV must be used too per...
  9. cry22

    Duct Sizing by Equal Friction Method using Varitrane Software

    I'd stay away from such software, it is hardly reliable. Take Trace 700 for example: It is what it is today because users like us keep sending questions regarding all sorts of bugs and ask for some wish lists to improve the software. Trace is at 30 years old and it is still full of bugs and keep...
  10. cry22

    DP sensor set point

    Time to move away from DP sensor set point. We are now the world of Static (or head) pressure RESET, see ASHRAE 90.1
  11. cry22

    are structural calcs required for commercial HVAC in America

    tstructural My two cents: 1. IBC certification? not aware of IBC certifying equipment. 2. Item #2 and #3 - healthcare and high tech or "high importance" (not just high tech) such as a control room in a prison - Requirements are needed for ALL seismic regions (not just medium and high) - we...
  12. cry22

    HVAC Design Software

    Irfan You are getting dangerous with your recommendations of using Revit for Load calcs. I have been using Trace since 1988 and have yet to master the software, so many things keep changing, from LCC, alternates, radiant heat, UFAD, ASHRAE 90.1 compliance, 62.1 built-in numbers, equipment...
  13. cry22

    return air outlet location

    Don't forget that you cannot return air from one room through another room (code violation) - i.e do not transfer air from rooms and return from the corridor (common mistake). Cannot use any room as a return air plenum.
  14. cry22

    A/C Area

    I said it here in teh past and I will say it again. HAP or Trace are not good software for residential single family type homes calculations (excluding high rise apartments). You should use manual J calcs fore residential, which substantially under-size equipment for residential (the way it...
  15. cry22

    Frost Protection on AHU Unit with Plate Heat Exchanger Heat Recovery

    Use face and by-pass on the wheel, by-pass the wheel when LAT (or EAT of OA after the wheel) is below freezing point. Look at ASHRAE it has LAT calculations formula - if you still can't find it, then we will. It is easy to give you the answer, but I think you should be able to dig it easily so...
  16. cry22

    Explaination of Same size Fan RPM with different Air Flow and Static Pressure

    Then they must have different wheel diameter, or different sheave.
  17. cry22

    2 heat 2 cool

    IRStuff Many of us here old timers don't have a clue of what you just wrote, Never heard of 2heat2cool business in 30 years. NOT just students.
  18. cry22

    Cooling Tower Equalizing Line

    I am not sure I understand the wording correctly. If you connect an equalizing line to the supply line, it is no longer an equalizing line, you need auto isolation valves to isolate a tower. Equalizing lines are usually made of PVC piping, no corrosion involved. You can do tower blow-down from...
  19. cry22

    Generator room ventilation

    317 air flow for radiator (when radiator part of gen set), combustion air flow, alternator cooling air flow.
  20. cry22

    Generator room ventilation

    Here is a source for details and schedules for most of young engineers that I am sure will find helpful http://www.cfm.va.gov/til/sdetail.asp check the emergency gen set detail from the same site below, this one has a radiator indoor, just edit to suit the remote radiator application. The...

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