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  1. Replies
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    1. Use a psychrometric chart with the protractor...

    1. Use a psychrometric chart with the protractor looking thing sitting above the saturation curve with sensible heat ratio markings on it.
    2. You take your space sensible heat ratio and plot that...
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    VRV or VRF + hydronic heat

    Apologies if this has been posted before, wasn't having much luck with my searching. I'm designing a job where we may be using a combination of a VRF with perimeter or radiant floor hydronic heat. ...
  3. Typically CO2 should be a maximum of 700-900 ppm...

    Typically CO2 should be a maximum of 700-900 ppm or a maximum of 400 ppm over ambient. Also sensors need to be calibrated and in every zone to make a VAV or multiple zone system work right with DCV....
  4. All of the above. Your local building code may...

    All of the above. Your local building code may have higher rates than would be determined based on a performance method based on people and occupancy or chemical contaminants as can be found in...
  5. Best bet in this scenario is to measure the...

    Best bet in this scenario is to measure the number of rows, tube size, face area and fin density (count the number of fins in 10cm). Then give that information along with the flow and return temps as...
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    Things to check: 1. Can your chemical go down...

    Things to check:
    1. Can your chemical go down the local sanitary sewer?
    2. Are storm and sanitary combined (like nyc)?If 1&2 are yes then you're done.
    3. If not then maybe you use containment and...
  7. Running VAV w/o reheat is doable but it requires...

    Running VAV w/o reheat is doable but it requires return air reset, average or critical space reset (easy with DDC boxes). For return air reset make sure that sensor doesn't see mixed air or you...
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    Line volt wiring not to code due to inadequate...

    Line volt wiring not to code due to inadequate support.
  9. Run through diagnostics with your LG rep. ICs can...

    Run through diagnostics with your LG rep. ICs can be damaged without it being visually apparent. IC damage is typically only functionally apparent.
  10. I've run into this on VRF units with the same...

    I've run into this on VRF units with the same story. You need a robust ground (CW lines don't cut it according to the engineering manuals, you need a proper grounding rod) and I'd suggest TVSS for at...
  11. Multistack like any other brazed plate condenser...

    Multistack like any other brazed plate condenser system cannot be used on open condenser systems due to fouling. Full stop. A proper multistack design must incorporate a plate and frame in the...
  12. If there are balance valves on the bypass legs...

    If there are balance valves on the bypass legs (there should be to mimic the pressure drop of the coil) then you can add VFDs to your pumps and go to variable flow pumping and save a boatload of...
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    This sounds like it could be a typical thermally...

    This sounds like it could be a typical thermally broken construction. The panels would overlap the frame on the unit interior so the frame isn't exposed to the air stream and the neoprene gasket...
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    Yeah Munters and similar desiccant systems are a...

    Yeah Munters and similar desiccant systems are a better option performance wise but I think $/CFM is too high for the developer. The architect won't give me the space either. My battle is for...
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    DX dehum makeup air units

    Looking at Reznor, Aaon, Daikin-McQuay Rebel, other mfg's hot gas reheat units. For a luxury condo corridor unit. Any experience good or bad? The Rebel is new, and I see a lot of substitutions to...
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    Retail, office, residential, everything. It has...

    Retail, office, residential, everything. It has to meet natural ventilation requirements or be provided with mechanical ventilation. Even when you satisfy natural vent requirements, there's no...
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    Min OA depends on occupancy. IMC2009 and ASHRAE...

    Min OA depends on occupancy. IMC2009 and ASHRAE 62 are 0.06 CFM per sq ft plus 5 CFM per occupant for most occupancies. Gyms, classrooms and other spaces with higher activity rates or space rather...
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    It's in all IMC based codes and just about...

    It's in all IMC based codes and just about everything else. When a space is occupied you have to ventilate it mechanically or naturally (5% of floor area in operable window free area and nothing more...
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    The economizer module also handles the min OA...

    The economizer module also handles the min OA position for ventilation needs during occupancy. If your OA and relief dampers aren't at least slightly open when your space is occupied, you likely have...
  20. Not sure. I wasn't on the survey, a colleague...

    Not sure. I wasn't on the survey, a colleague took the picture. We were only concerned about moving flues out of the way of some planned higher work. This was interesting but out of my scope.
    ...
  21. Gooseneck + Exhaust fan = Exhaustneck or Goosefan?

    Nice, eh?
  22. Replies
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    I used to work in patents. Patent quality is...

    I used to work in patents. Patent quality is often so incredibly poor. Things that ought not to have been patentable get patent protection due to sloppy prior art examination. Also the people who are...
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    Copper can be easier to deal with if you don't...

    Copper can be easier to deal with if you don't want to pay attention to water quality on closed systems. Copper won't develop flaky rust prior to installation which can be a problem when...
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    Shouldn't the fan starter or VFD have contacts...

    Shouldn't the fan starter or VFD have contacts for shutdown by the FAS? The controls either keep power and are aware the FAS has shut down the fan or could also lose power and shut the unit down...
  25. At nominal 200-250 of borehole ft/ton equipment,...

    At nominal 200-250 of borehole ft/ton equipment, that sounds like it would be 20 to 25 k to drill plus equipment and installation less the tax credit. Which isn't bad, I guess. I'm not sure how...
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    Typically existing only needs to comply with the...

    Typically existing only needs to comply with the code in force at the time of building permit for the work being done. Certain activities will trigger a need to comply with current code. Basic...
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    In an office with lots of rooms and one stat it...

    In an office with lots of rooms and one stat it will help keep the air turned over and reduce hot rooms when rooms have loads out of balance. But if the RTU is not intended to provide ventilation fan...
  28. Agree. Resi is not the place for complex...

    Agree. Resi is not the place for complex controls. Although, I've had a job or two come through my office where something like that would be applicable due to the scale of the project. But those are...
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    Wrong voltage? More likely, too much airflow or...

    Wrong voltage? More likely, too much airflow or static. Did you check amps? Another possibility is if you're drawing through a heating section, excessive air temps.
  30. If you went with Mitsubishi, you'd put small DX...

    If you went with Mitsubishi, you'd put small DX fan coils in each room and a hydronic heat exchanger on a recirc loop with domestic. They have a product called HydraDan that's just like Altherma but...
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    thanks techreptdh

    Thanks again. Never heard that before. I'll start putting that in my TAB specs. There also appears to be a distinct operational advantage to removing adjustability after TAB so that someone silly...
  32. 1. You could set the ground side up as variable...

    1. You could set the ground side up as variable primary and variable secondary. The equipment controls its circulator to get the ground water flow it wants and then your main pumps could control to...
  33. First cost and design cost has always been an...

    First cost and design cost has always been an issue with GSHP. If its cheap and easy to put pipe in the ground where you are, GSHP is great, but you need to make sure you have enough pipe in the...
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    Ventilation is required in occupied mode

    And you can't ventilate continuously during occupancy times without the fan running. That is a code requirement in all NYC 1968 code, NYC new code, IMC based jurisdictions, CA and probably...
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    Typically all of that stuff is provided packaged...

    Typically all of that stuff is provided packaged by the VFD vendor. The local rep may or may not understand this stuff, so call the rep and then if you don't get a clear or convincing answer escalate...
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    Yeah. Sorry about that. I think a lot of...

    Yeah. Sorry about that.

    I think a lot of older VAV box controllers have proprietary interfaces with the stuff that goes on the wall. Basically any analog electric VAV controller will be...
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    Nice. Didn't notice the date on the drawing. The...

    Nice. Didn't notice the date on the drawing. The interface between the VAV controller and the wall sensor looks non standard. If you can't find the stat you could just replace the VAV controller with...
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    FPB without fan control...

    make sure you wire up the fan relay somehow. Titus aren't showing that. the fan will run 24/7 on this if it's just line voltage. typically you only want to run the fan when the AHU is running or...
  39. I'm specifying TVSS at the disconnect or panel by...

    I'm specifying TVSS at the disconnect or panel by electrical on all my VRF jobs for the system. They do not seem hardened against surges. Also Daikin has a warning about grounding and checking the...
  40. Replies
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    Nest self programs based on an occupancy sensor,...

    Nest self programs based on an occupancy sensor, user input and measured system responses. Most VAV AHU controllers won't even adjust PID gains automatically. It has limitations in application and...
  41. Replies
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    100% OA needs discharge air temp control with a...

    100% OA needs discharge air temp control with a heating cooling and neutral setpoint based on t-stat calls. Then it also needs to dehum to maintain max leaving air dewpoint or at least max space RH....
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    Put utility submeters on your plant. Put Btu...

    Put utility submeters on your plant. Put Btu meters on your plant. Take the consumption and demand share of the utility bill for the plant and parcel it out to tenants based on their monthly W hr...
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    I used to work in a patent law firm. I moved to...

    I used to work in a patent law firm. I moved to HVAC for a reason. Patent law is a much better way to make money than HVAC, but HVAC is more fun and saving Btu's saves the world (at least I hope it...
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    The basis of design may be a different level of...

    The basis of design may be a different level of comfort than we typically design to with this kind of aystem, and the client might not have understood the implications. If the solution is adding...
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    Get a DC bus choke. Most facilities I deal with...

    Get a DC bus choke. Most facilities I deal with are ABB or Yaskawa as basis of design, but that doesn't mean other companies don't make good stuff.
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    Where is this?

    Where is this?
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    Suggest move to AOP commercial... There are a...

    Suggest move to AOP commercial...

    There are a couple of ways. Some details about how it should or can be done should be included in the lease agreements the tenants have signed.

    1. Use the sum...
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    I like that you're checking the OA damper...

    I like that you're checking the OA damper position, but if the facilities guys closed the OA damper over the winter "to save energy" or "because it was cold" the unit needs to be rebalanced for the...
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    KSA is 230/380 like most of EMEA but they're 60...

    KSA is 230/380 like most of EMEA but they're 60 Hz. Equipment out there all has beefier condenser fans due to high ambient (120 F). Water cooled comes into play for district systems.
  50. This was done in Vancouver for the Olympics. Also...

    This was done in Vancouver for the Olympics. Also been done in Scandinavia for district heating systems.
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