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  1. GT-EGR

    dP Sensor Location & PICV's

    The 2/3 rule always seemed like a vague way for someone to easily call out a sensor spot without putting too much thought into it, mostly because it can be complex in theory but then you can install it in different spots and still get it to work out. The PICV will handle the over pressure...
  2. GT-EGR

    Medium pressure ductwork

    Still would be done the same way, using a damper or a VAV box which is basically an automatic damper to drop the pressure and regulate flow quantity before it is discharged into the space. Or you said valve which in a critical space is a particular type of Venturi which again just reduces the...
  3. GT-EGR

    CO2 Air to Water Heat Pump w Solar Pre-heat

    The way this information is being presented I think is the confusing part. Yes as the entering temperature gets higher, you get less heat pump heating output aka lower efficiency. This is just due to the ability to transfer heat from the refrigeration cycle if the water starts off...
  4. GT-EGR

    How well do cooling only VAV's with perimeter heat work?

    My experience is that the interior office type spaces you can usually get away with it since the minimums are so low. But the conference room high occupancy high minimum airflow spaces are the issue. You can resolve those by using minimum ventilation reset strategies which is somewhat code...
  5. GT-EGR

    Exhaust for Cannabis Cultivation

    Code doesn’t specifically require exhaust for cannabis cultivation itself. But some of the supporting elements of the operation like CO2 use and making sure you have protections and purge capabilities during accidental release would end up indirectly leading you to exhausting certain areas that...
  6. GT-EGR

    How much pressure is required by an exhaust fan when it exhausts straight up?

    Calculating on the exhaust discharge side is barely any different than on the suction inlet side You do your normal calculation and fitting loss lookups based on your exhaust airflow, and the duct size and velocity the air is traveling through. You also may have to account for velocity...
  7. GT-EGR

    Vav with FCU

    I would guess that the FCU is recirculating in the space so provides heating and cooling but no ventilation. Then the VAV provides ventilation air to the space, but not at a quantity near enough to cool or heat the space. I also see this a lot in labs with high cooling loads (FCU sized for it)...
  8. GT-EGR

    DIVERSITY FACTOR - HEAD PUMP - CHILLED WATER SYSTEM

    Here’s an example of a simple approach that is slightly conservative and doesn’t take much any extra effort. Let’s say you have 4 coils that each need 60 GPM, but your max load is 200 GPM. Identify your critical run, and do the pressure loss calc of the most remote branch at 60 GPM, when it...
  9. GT-EGR

    Reset pressure setpoint method and primary pump variable speed

    It’s very similar to the traditional way where you picked a DP reading and target setpoint somewhere remote in the system. Major install difference is you need feedback on the valve positions to your controller. Otherwise pick and design to a starting DP setpoint as you always would have...
  10. GT-EGR

    Reset pressure setpoint method and primary pump variable speed

    Secondary loop differential pressure reset algorithm generally takes feedback of some or all of the critical chilled water consumers in the loop, decides if a high quantity or all of the valves are in need of that much flow/pressure, and then resets the DP setpoint up or down in response to...
  11. GT-EGR

    Hydronic pressure loss mystery

    Twice in the past year we lost boiler pressure to the point of tripping the low water cut off devices - have you ruled out that the low after cutoff is functioning properly? I assume this 6th floor boiler is above a significant volume of the building loops it feeds correct? You’d have to...
  12. GT-EGR

    Building Pressurization

    A value like that is useful to plan some extra outside air capacity. But it really all depends on what your control method is, how tall your building is, and how extreme your summer and winter temperatures are. I’ve never seen an all encompassing approach because building pressure targets are...
  13. GT-EGR

    Ethylene or Propylene glycol for HVAC system

    See attached, just came across this brief summary in ASHRAE journal last November article about runaround glycol heat recovery loops. https://files.engineering.com/getfile.aspx?folder=f9c004f3-3101-4b8f-9745-92d46302e027&file=BC1208C7-1BDC-4718-BBF3-92F500DC7DD5.jpeg
  14. GT-EGR

    Ethylene or Propylene glycol for HVAC system

    I trace back the anti-EG sentiment to the link below. Heavily regulated and compliant Facilties see EG as one more potential item to track. PG doesn’t have anything out there like this so it is casually regarded at times as the safe alternative. https://rcrapublic.epa.gov/files/14163.pdf
  15. GT-EGR

    Walk-in Cooler/Freezer Demo

    Only thing I’d add to these answers is if you don’t remove the outdoor unit at least label it as abandoned and what it used to do. In a building with a lot of condensers this can sometimes be a big help to us poor engineers trying to trace out tiny refrigerant piping.
  16. GT-EGR

    Why Chilled Water Supply Should be Under 5°C/42°F?

    Low operating temperature for chilled water is regularly used when you need want dehumidification capabilities from a CHW coil. Since it is a lower temperature, it can cool air to a much lower temperature and extract more moisture out of the air. If the chiller serves a process and not HVAC...
  17. GT-EGR

    Duct fitting pressure loss factor for industrial fan sizing

    In addition to just using the closest ASHRAE equivalent available - I’d see if there is a trending difference as you move from Ashrae’s smallest to largest sizes with the same type of fitting. Maybe you’ll find that as you get larger but keep the same relative geometry and velocity that larger...
  18. GT-EGR

    McQuay Psychrometric Analyzer

    The dry bulb and wet bulb temperature you want to cool all that air down to. Do you want to take that mixed air temp down to 60 degrees saturated (just put 60 as top number and it will auto fill a saturated wet bulb)50 degrees saturated? Somehow you got 2880 CFM - probably based on a supply...
  19. GT-EGR

    HVAC Calculators

    Thanks, a lot of these are helpful. Don’t take this as criticism, I’m thankful for anyone who takes the time to make others lives easier for free. Feedback on two of them The air change calculator - often we need to do the calc in reverse (we know airflow and room size - what air change is...
  20. GT-EGR

    hvac,air movement, static pressure,ESP

    The reference standard would be the manufacturers stating and testing and standing by the unducted performance of the fan. I guess you could ask them for their testing documentation? If there is no ductwork, the fan is just free flowing air from atmosphere to atmosphere. All it needs pressure...

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