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  1. Replies
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    Yes. It’s pretty standard operation. The savings...

    Yes. It’s pretty standard operation. The savings are larger if the chillers are variable speed, but it’s true for fixed-speed as well.
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    557

    It is more common to have multiple chillers, all...

    It is more common to have multiple chillers, all of which are in operation. For example, if you have a building with a 1000 ton design load, you might have two 600-ton chillers so that if one goes...
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    One reason is microchannel evap and...

    One reason is microchannel evap and condensers.Also, I believe the current refrigerants run at higher pressure than the older refrigerants, so smaller tubes.
  4. Replies
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    220

    No - there are no more energy efficient electric...

    No - there are no more energy efficient electric furnaces. Every electric furnace is nearly 100% efficient - the problem is the cost of the electric itself. Yes, a mini- or multi-split that gives...
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    You should consider a multi-split with either...

    You should consider a multi-split with either high-wall mounted units (probably the best choice) or low-profile ceiling-mounted cassettes. With the wall-mounted unit ceiling height is not an issue....
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    For York products J07 almost always means 7.5...

    For York products J07 almost always means 7.5 tons.
  7. Replies
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    Yes, it is. Here is an excellent article on the...

    Yes, it is. Here is an excellent article on the topic. Read the comments too. A lot of very knowledgeable people contributed.
    ...
  8. 4 to 8 ventilation air changes per hour is more...

    4 to 8 ventilation air changes per hour is more than most hospital spaces require. As noted by others, unless there is something special about what is to be stored, or there is vehicle traffic that...
  9. Replies
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    314

    When Nirvana told you that the fault was sand in...

    When Nirvana told you that the fault was sand in the HX, what had you told them to make them arrive at this conclusion?
  10. The coil wraps around, and those are slots to...

    The coil wraps around, and those are slots to allow the air to flow over the side of the coil.



    Hot air floats up and is trapped under the deck. There is negative pressure over the unit, so a...
  11. While the overhead clearance is an issue, your...

    While the overhead clearance is an issue, your biggest problem is the lack of clearance between the wall and the unit. Airflow is going to be terrible. While this might not hurt the unit, it will...
  12. Replies
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    498

    When you have a fan downstream of the coil, the...

    When you have a fan downstream of the coil, the air pressure at the drain pan is less than atmospheric pressure. Without a P-trap air would actually be sucked into the AC unit through the pipe and...
  13. While the suggestions above may be correct, I...

    While the suggestions above may be correct, I think there is a good chance that it is residual oil on the fins from when they were stamped into shape prior to assembly of the coil. I used to run a...
  14. Replies
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    I just noticed that I mistyped the blend of...

    I just noticed that I mistyped the blend of R-410A. It's 50-50 R-32 and R-125.
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    The change happened fairly early in my career...

    The change happened fairly early in my career with a big AC manufacturer, and I was not in compressorized products at the time, so I am not 100% sure about this, but pretty sure:

    Back then, the...
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    566

    Disclaimer - I am not an engineer and do not have...

    Disclaimer - I am not an engineer and do not have specialized knowledge in this area. These are my thoughts based on my years working for an air handler company and chatting with lots of engineers....
  17. Replies
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    406

    Could be that at the time the basement was...

    Could be that at the time the basement was finished the homeowner was planning for a future ducted AC system.
  18. Replies
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    357

    A relative humidity of 45% is lower than...

    A relative humidity of 45% is lower than necessary, but not bad for you or the humidifier. 60% humidity is considered the upper limit to avoid mold growth and most buildings in humid areas are...
  19. Replies
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    347

    For what it's worth, here is the definition of...

    For what it's worth, here is the definition of plenum from ASHRAE 90.1:

    plenum: a compartment or chamber to which one or more ducts are connected, that forms a part of the air distribution system,...
  20. Replies
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    Yes, it's technically possible, but not a good...

    Yes, it's technically possible, but not a good idea to try to kluge it together. You can buy ducted multi-split systems. The only question would be whether the fan coils could be installed where your...
  21. Replies
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    The VFD is probably the way to go, but here are...

    The VFD is probably the way to go, but here are some other thoughts:

    1. I noticed that the high-static fan was selected. If you do not actually have high static pressure to overcome, you may be...
  22. Replies
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    685

    This post really should be in the chillers open...

    This post really should be in the chillers open forum. You would get better answers there. Though you are designing for residential units, this forum is for the type of equipment that goes into...
  23. You can measure at the return grille if the...

    You can measure at the return grille if the following conditions are met:

    1. That grille is the only source of return air to RTU or you are highly confident the dry bulb and wet bulb at the other...
  24. Deleted - mistaken answer

    Deleted - mistaken answer
  25. This is required in a reverse-return system so...

    This is required in a reverse-return system so that the difference in the water column height of the supply and return risers is the same on each floor.
  26. Yep, that is a reverse return system. The idea is...

    Yep, that is a reverse return system. The idea is that the difference in pressure between the supply and return will be the same on all floors. With the growth of variable speed pumping and...
  27. Replies
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    Just curious - what State is using this for a...

    Just curious - what State is using this for a rebate program?

    I also wonder if by "heat economizer" the rebate program really means a device that recaptures heat from the flue. I searched the...
  28. Replies
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    I agree with @Malmo. That equation does not make...

    I agree with @Malmo. That equation does not make sense. Which ASHRAE book is it from? Can you post screenshot of the page?
  29. Thread: Solx energy

    by coolcoil
    Replies
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    1,032

    This system is a fraud. Adding heat to...

    This system is a fraud. Adding heat to compressed refrigerant before the refrigerant enters the condenser would only reduce the cooling performance. Any heat added to the gas would only increase...
  30. Replies
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    That is correct - Europe accounts for water...

    That is correct - Europe accounts for water pressure drop through the chiller only. I was at the ASHREA meeting this week and was told at one meeting that AHRI is considering doing the same in...
  31. Replies
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    Agreed. Manufacturer-rated chiller performance...

    Agreed. Manufacturer-rated chiller performance does not include tower or pump power.
  32. Replies
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    16,527

    Using waste heat from a building to supplement...

    Using waste heat from a building to supplement pool heating has been done for a long time. It is very common in schools and gyms. I've not heard of it being done on a house, but I suspect that is...
  33. As far as I know, there are not any packaged...

    As far as I know, there are not any packaged air-cooled mag bearing chillers on the market. If there are, I'd like to see some links, as I think it's a product that would be valuable.

    Assuming...
  34. Replies
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    I don't disagree with your assessment. However,...

    I don't disagree with your assessment. However, I was talking about the location of the cooling coil upstream or downstream of the fan, not the location of the HX. As noted above, the HX must...
  35. Replies
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    I suspect that in residential systems the coils...

    I suspect that in residential systems the coils are typically after the fans because the coil section is an add-on to the furnace. Ideally, you would stick the coils below the furnace instead of on...
  36. Replies
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    Fans are always upstream of gas heat exchangers...

    Fans are always upstream of gas heat exchangers for safety reasons. Any combustion HX needs to be in the positive pressure section of the air handler so that if it leaks, the products of combustion...
  37. Replies
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    1,498

    Other than putting on a soft starter, how would...

    Other than putting on a soft starter, how would you fix too much torque? The only two options that I can think of are:

    1) Put on a smaller motor, which may or may not have enough power to operate...
  38. Replies
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    Ah...I did not pick up on that, even though it...

    Ah...I did not pick up on that, even though it was mentioned in a previous post. So multiple sheave (non-adjustable) would be the way to go. Or a soft starter, though I think that would be a less...
  39. Replies
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    1,498

    This is exactly the right question to ask. The...

    This is exactly the right question to ask. The problem is not a poor quality belt. The problem is that you don't have enough contact surface between the belt and the pulleys, and that's why you...
  40. Replies
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    I work for York, though not in the Chiller group,...

    I work for York, though not in the Chiller group, so take this for what it's worth:

    York Titan OM chillers are extremely large custom-made chillers. They are designed for each job. There are not...
  41. Replies
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    1,813

    Actually, I was told this by one of the...

    Actually, I was told this by one of the manufacturers of compressors that are suppliers to some of the companies listed earlier in this thread. I was involved with the early stages of the redesign...
  42. Replies
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    812

    First try closing the vent into the basement, as...

    First try closing the vent into the basement, as it would achieve the same thing. Both that and insulating will reduce the quantity of heat entering the basement.

    Is the ceiling of the...
  43. Replies
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    ASHRAE just recently published Guideline 36 -...

    ASHRAE just recently published Guideline 36 - High Performance Sequences of Operation for HVAC Systems. It has recommended sequences for VAV systems. It is a compilation of the latest research and...
  44. Replies
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    Digital scrolls? They have long since been sent...

    Digital scrolls? They have long since been sent to the dustbin of history. They were just a temporary answer back when very few companies had variable speed drive technology for compressors. ...
  45. Replies
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    1,813

    I assume you are doing this for LEED credits. If...

    I assume you are doing this for LEED credits. If so, you will likely get a better answer on one of the many LEED forums out there. Whether LEED will accept something as "new" technology can be...
  46. Replies
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    Yep - both of the above are true, though the coil...

    Yep - both of the above are true, though the coil temp difference will be very small. The filters are a bigger problem, and we have definitely seen that happen. In the article that I linked, the...
  47. Replies
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    2,112

    It is true that if you have two identical fans...

    It is true that if you have two identical fans running at the same speed, and the one with the higher density entering air will use more power because it is moving a larger mass of air. In the...
  48. Replies
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    I am an engineer for a large company that makes...

    I am an engineer for a large company that makes air handlers. This is a very common question.

    In North America, it is much more common to place the fans after the cooling coil. This is called...
  49. Replies
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    The cassette unit itself could be dirty and/or...

    The cassette unit itself could be dirty and/or have mold growing in it. Go on Youtube and enter "cleaning VRF fan coil" and you will have your eyes opened. VRF has a lot of good things going for...
  50. Replies
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    686

    300 GPM for a 200-ton chiller is a typical flow...

    300 GPM for a 200-ton chiller is a typical flow in new designs. It yields a design temperature rise of 16 degrees F. The days of 2.4 GPM (10 degrees rise) are passing, though there are still a lot...
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