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  1. lilliput1

    Heat Gain for Computers

    Using 1/3 the full rated power use of electrical equipment is a good approximation.
  2. lilliput1

    Use of recirculated air as a make up in clean rooms?

    The outdoor air required must equal the exhaust air plus the air required to pressurize the space. This would be more than that required for ventilation. You can not reintroduce exhaust air into the space. You need to add DX cooling coil to the makeup air system and introduce some of the supply...
  3. lilliput1

    Electric Water Heaters in Mechanical Closet Plenums

    You have to work with the architect to provide you with space to run return air ductwork within the closet to meet code requirement.
  4. lilliput1

    Determine right pressure setpoint

    Ok then if the 3rd loop really turns out to the the run resulting in highest pressure drop then the differential pressure setpoint will be the pressure drop through the piping, fittings, equipment and valves through the 3rd branch loop. For balancing all equipment should have combination...
  5. lilliput1

    Pump calculation in high rise continued

    You have to break off piping loops to not exceed pipe equipment pressure rating by using separate heat exchanger for each loop. Allow for approach temperature difference between fluids and always design for counterflow.
  6. lilliput1

    Single duct several diffuser

    You have to understand that for a ductwork system to be balanced to design flows the air pressure drop to each diffuser must match the pressure drop to the most remote diffuser. Note the fan discharge pressure must be dissipated to zero which is the pressure at each air outlet. So plan on...
  7. lilliput1

    Energy Reclamation Project

    Are you sure the heat from the exhaust air in not recycled by it passing through the approximate half of the desiccant enthalpy wheels while outdoor air for the intake air blower goes through the other half of the wheels thereby absorbing the heat from the exhaust air as the wheels rotate? There...
  8. lilliput1

    Design of the ducts and outlet surfaces

    You need to have fire damper, access door, and volume dampers to create pressure drop such that the pressure drop here can equal the pressure drop from the main to the worst run of ductwork so flows can be balanced to design values. So fogure on FD w/ AD then Y split and total 4 branches spaced...
  9. lilliput1

    Determine right pressure setpoint

    Moideem you are confusing a pressure regulating valve for a differential pressure sensor. The pressure regulating valve is not used to control AFD pumps.
  10. lilliput1

    Formula help Please

    Instead of coming up with a formula why not sort all the rows and column with ascending X value then the the left and right hand part number and their location number will be displayed next to each other. If you are looking for a specific value in a particular column you can make it easier to...
  11. lilliput1

    Hydronic pressure loss mystery

    Did the pressure drop when the pumps were turned on?
  12. lilliput1

    Ahu coil Pump

    Don't mess with it if it is for preheat coil freeze protection using preheat heating water. It works fine.
  13. lilliput1

    Determine right pressure setpoint

    First off the location of the differential pressure is wrong. The high and low pressure sensor of the DPS are located at the same pressure point so here is no differential. Second you should delete the end of the loop connection because you are just providing a bypass that would negate the use...
  14. lilliput1

    Is pumping away from chillers technically okay?

    To be ok the following must be met: the NPSH at the pump inlet must be greater than the pump minimum NPSH requirement; air in the piping must be automatically vented by automatic air vents located at all high points of piping; the expansion tank initial pressure must be set such that minimum 10...
  15. lilliput1

    Uneven heating on HVAC heating coil (air-water HEX, copper fin tube)

    There should be a strainer on the HWS piping upstream of the coils. There should be a manual air vent valve at the top of each coil and automatic air vents at the high point of the HWS and the HWR piping above the coils. There should have been plugged tees at each coil offset HWS and HWR piping...
  16. lilliput1

    Condensation Problems in multiple rooms

    I have run across this. Now in normal HVAC design the space is pressurized with conditioned outdoor air at about 0.5 CFM/SF to prevent infiltration of outdoor air. The condensation is caused by infiltration of outdoor air which is caused by 2 things. First there is a crack or opening that lets...
  17. lilliput1

    Pump suction strainer dilemma

    How about using filters in parallel valved manifold and differential pressure gauges so you can shut and replace one while the other is in service. Consult filter manufacturer to determine size and filtration capability.
  18. lilliput1

    Why do portable ACs have filters for the evaporator but not the condenser?

    The filter is for the air supply going into the room. The condenser coil (or cooling coil in reversed heat pump operation) discharges air to the outdoors so it is not filtered.
  19. lilliput1

    Uneven heating on HVAC heating coil (air-water HEX, copper fin tube)

    Can the coil be piped reverse return? Either reconfigure the return or the supply to accomplish this.
  20. lilliput1

    minimum air intake distance between two cooling towers

    The engineer may have oversized the cooling towers per manufacturer’s recommendation to make up for this installation.

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