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  1. lucaspenalva

    Maintenance X Operation X Planning department

    Hello there. How is maintenance structured at your site? I mean, how is the interaction between maintenance, operation and Planning department? Who's " the boss"? Does Operation have the autonomy to allow or not a maintenance service to happen? Does planning dept plan activities without...
  2. lucaspenalva

    Acceptable current unbalance in three-phase motor

    Hello there guys, thank you all for your inputs so far! It's a 60 HP motor (nominal current @380V = 84,5 A). So to check the cause of current unbalance, I should then swap phases and see: -if current unbalance is still present in the same motor phase, its a winding/motor problem; -if current...
  3. lucaspenalva

    Acceptable current unbalance in three-phase motor

    @waross Thanks for your input !! Here's measured voltages: R-S = 384 V S-T = 383 V R-T = 382 V That's 0,3% unbalance. Therefore current unbalance is 8,7 times greater than voltage unbalance (= 2,5% / 0,3%). I've looked up that current unbalance can reach up to 10 times voltage unbalance. Is...
  4. lucaspenalva

    Acceptable current unbalance in three-phase motor

    Hello there, What are acceptable ranges of current unbalance in three phase motor? Considering: current unbalance = (max deviation from average current) / average currrent I have this motor that powers a pump: R=87 A S=91 A T=88 A AVERAGE = 88,7 A MAX DEVIATION FROM AVERAGE = 2,3 A CURRENT...
  5. lucaspenalva

    Estimating refrigerant recharge

    I want to predict how much i must expect to charge it. using calculation method. that's prior to charging itself and monitor subcooling and superheat to adjust charge. i dont want to drain it and recharge it. anybody has a objective method?
  6. lucaspenalva

    Estimating refrigerant recharge

    i have chiller with leak. after correcting leak, how can i estimate how much refrigerant to recharge?
  7. lucaspenalva

    How TXV controls flow?

    If positive displacement compressor (such as scroll) has constant flow no matter the resistance in the system, how can TXV control flow? Or it doesn't?
  8. lucaspenalva

    Pressure independent balance and control valve issue

    I have a system with several fancoils with pressure independent balance and control valve (IMI HYDRONICS TA FUSION-P 50) However, some of them are showing strange behavior: In automatic mode, at some point during operation, even though valve actuator is fully open there is no flow, so...
  9. lucaspenalva

    HVAC load calculation (former TRACE 700 user)

    Nice feedback. By the way, do you like your results for duct calculations with Revit? I always get wierd pressure loss in fittings.
  10. lucaspenalva

    Parallel or primary/backup operation - which is best?

    Hi there guys, In which type of operation (parallel or primary/backup) will chillers and pumps last longer? As: Parallel = more working hours more less stress primary/backup = less working hours / more stress
  11. lucaspenalva

    HVAC load calculation (former TRACE 700 user)

    Try CYPETHERM LOAD. It uses RTS and it's free trial. http://cypetherm-suite.en.cype.com/ What about Revit for load calculation? Although you are looking for software, what about excel sheet? It's simple as you want. offtopic = I wonder how good is Revit for duct calculations - specially when...
  12. lucaspenalva

    HVAC For E-House

    Manufacturer requests ventilation openings (with proper filtration!) to provide cooling in case you don't have HVAC unit. If you have HVAC unit, you'll only need a little bit of ventilation to keep positive pressure and avoid infiltration of untreated air.
  13. lucaspenalva

    typical hotel room hourly occupation profile

    @LittleInch, By 'typical hotel' I mean I don't have interest in those 6+ stars extremely luxury hotels - but anything below that would be highly appreciated, including business, budget and vacation hotel. In fact, right now I'm doing a study for a business hotel, so I can say it's my priority...
  14. lucaspenalva

    typical hotel room hourly occupation profile

    What I am looking for is typical hotel guest room occupancy schedule for central cooling plant sizing and energy consumption analysis during design period. I have found this information in the link below: https://www.energycodes.gov/development/commercial/prototype_models It's not for control...
  15. lucaspenalva

    typical hotel room hourly occupation profile

    Hello there, I'm doing a study on hotel's chiller sizing and I'm looking for a typical hotel room hourly occupation profile. That is: From all room that were sold, how many are actually occupied (guest is inside the room), for every hour of the day? Example: - 11a.m. = 20% (100 sold rooms...
  16. lucaspenalva

    Why pumps might not cavitate when NPSHa < NPSHr? Why smaller pumps hardly cavitate?

    Thank you all for your inputs.
  17. lucaspenalva

    Why pumps might not cavitate when NPSHa < NPSHr? Why smaller pumps hardly cavitate?

    Hello there, It is known that NPSHr provided by manufacturer is measured as the point at which the differential head drops by 3%. Therefore, it doesn't necessarily means that it will (100% for sure) cavitate when NPSHa < NPSHr. But why is NPSHr is measured like this? Why in fact cavitation may...
  18. lucaspenalva

    Reference pressure in closed loop pumping system without tank

    Thank you all for your feedback. It really helped me better understand thermal expansion tanks and reference pressures in closed systems! Hope you all have a great week!
  19. lucaspenalva

    Reference pressure in closed loop pumping system without tank

    Sorry guys, "mca" stands for (in my native language) meter of water column. So in the example I gave, there is no way to predict what will be the pressure at pump inlet? By the way, what are alternatives to expansion tanks?
  20. lucaspenalva

    Reference pressure in closed loop pumping system without tank

    How to determine reference pressure and its location in a closed loop pumping system without tank? I've drawn a really simple layout so we can work on it. Imagine a system basically composed by a pump and 2 heat exchangers located 10 meters above pump. No openings to atmosphere and no...

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